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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Mech. Eng</journal-id>
<journal-title>Frontiers in Mechanical Engineering</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Mech. Eng</abbrev-journal-title>
<issn pub-type="epub">2297-3079</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="publisher-id">1225682</article-id>
<article-id pub-id-type="doi">10.3389/fmech.2023.1225682</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Mechanical Engineering</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Kirigami-inspired deployable mechanisms with a type-preserving feature and controllable Poisson&#x2019;s ratio</article-title>
<alt-title alt-title-type="left-running-head">Wang et al.</alt-title>
<alt-title alt-title-type="right-running-head">
<ext-link ext-link-type="uri" xlink:href="https://doi.org/10.3389/fmech.2023.1225682">10.3389/fmech.2023.1225682</ext-link>
</alt-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Wang</surname>
<given-names>Jianzhi</given-names>
</name>
<uri xlink:href="https://loop.frontiersin.org/people/2178873/overview"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Xiao</surname>
<given-names>Hang</given-names>
</name>
<uri xlink:href="https://loop.frontiersin.org/people/2178689/overview"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Ding</surname>
<given-names>Xilun</given-names>
</name>
<uri xlink:href="https://loop.frontiersin.org/people/789572/overview"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Lyu</surname>
<given-names>Shengnan</given-names>
</name>
<xref ref-type="corresp" rid="c001">&#x2a;</xref>
<uri xlink:href="https://loop.frontiersin.org/people/2178775/overview"/>
</contrib>
</contrib-group>
<aff>
<institution>Robotics Institute, School of Mechanical Engineering and Automation, Beihang University</institution>, <addr-line>Beijing</addr-line>, <country>China</country>
</aff>
<author-notes>
<fn fn-type="edited-by">
<p>
<bold>Edited by:</bold> <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/265018/overview">Andreas Mueller</ext-link>, Johannes Kepler University of Linz, Austria</p>
</fn>
<fn fn-type="edited-by">
<p>
<bold>Reviewed by:</bold> <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/1717282/overview">Fengyu Xu</ext-link>, Nanjing University of Posts and Telecommunications, China</p>
<p>
<ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/1501664/overview">Nicola Cappetti</ext-link>, University of Salerno, Italy</p>
</fn>
<corresp id="c001">&#x2a;Correspondence: Shengnan Lyu, <email>shengnan_lyu@buaa.edu.cn</email>
</corresp>
</author-notes>
<pub-date pub-type="epub">
<day>16</day>
<month>11</month>
<year>2023</year>
</pub-date>
<pub-date pub-type="collection">
<year>2023</year>
</pub-date>
<volume>9</volume>
<elocation-id>1225682</elocation-id>
<history>
<date date-type="received">
<day>19</day>
<month>05</month>
<year>2023</year>
</date>
<date date-type="accepted">
<day>10</day>
<month>10</month>
<year>2023</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2023 Wang, Xiao, Ding and Lyu.</copyright-statement>
<copyright-year>2023</copyright-year>
<copyright-holder>Wang, Xiao, Ding and Lyu</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p>
</license>
</permissions>
<abstract>
<p>A spatial deployable mechanism is capable of adapting to different operating requirements by adjusting its shape and size. However, most current deployable mechanisms fail to maintain the type of their reflective surface during the folding process, which limits their ability to adjust the optimal operating frequency. To address this issue, this paper presents a novel design of a deployable mechanism with a type-preserving feature inspired by kirigami techniques. By preserving the type of its reflective surface, this mechanism allows for the adjustment of the optimum operating frequency according to specific requirements. This makes it well-suited for deployment on commercial satellites that undergo constant mission variations. The mechanism is constructed using porous kirigami cells, ensuring that the type of the working surface is maintained throughout the deployment process. The construction of deployable units and networks based on porous cells is also discussed. Additionally, deployable mechanisms with controllable Poisson&#x2019;s ratios are developed. The kinematics of the mechanism are analyzed to verify the type-preserving characteristics. Finally, four case studies are conducted to illustrate and validate the proposed design and analysis.</p>
</abstract>
<kwd-group>
<kwd>kirigami</kwd>
<kwd>deployable mechanism</kwd>
<kwd>type preserving</kwd>
<kwd>controllable Poisson&#x2019;s ratio</kwd>
<kwd>cylindrical surface</kwd>
</kwd-group>
<custom-meta-wrap>
<custom-meta>
<meta-name>section-at-acceptance</meta-name>
<meta-value>Digital Manufacturing</meta-value>
</custom-meta>
</custom-meta-wrap>
</article-meta>
</front>
<body>
<sec id="s1">
<title>1 Introduction</title>
<p>A deployable mechanism can be compactly folded into a small size for easy transportation and expanded to a large structure at working conditions, meaning they have been widely utilized in different applications (<xref ref-type="bibr" rid="B4">Ding et al., 2020</xref>; <xref ref-type="bibr" rid="B15">Shi Chuang et al., 2021</xref>; <xref ref-type="bibr" rid="B8">Lim et al., 2022</xref>). Many studies on deployable mechanisms have been conducted in recent years. Ramadoss et al. summarized a family of deployable mechanisms that approximated a series of curves and surfaces using the polygonal approximation technique (<xref ref-type="bibr" rid="B12">Ramadoss et al., 2019</xref>). Xu et al. designed and analyzed a truss deployable antenna mechanism based on a 3UU-3URU unit (<xref ref-type="bibr" rid="B18">Xu et al., 2019</xref>). Duan provided a survey of research activities of Large spaceborne deployable antennas (LSDAs) in the past, present, and future (<xref ref-type="bibr" rid="B5">Duan, 2020</xref>). Dai and Xiao designed a new deployable truss structure for large caliber antennas (<xref ref-type="bibr" rid="B3">Dai and Xiao, 2020</xref>).Shi et al. proposed a new type of cable-strut antenna mechanism; optimization of the mechanism synthesis was established (<xref ref-type="bibr" rid="B14">Shi C. et al., 2021</xref>). Most researchers focus on the folded and deployed states of deployable mechanism while ignoring the intermediate configuration. The deployable mechanism will be sufficiently utilized if the intermediate state can maintain a type similar to that of the deployed state.</p>
<p>Kirigami is a combination of paper cutting and folding. It can obtain a three-dimensional structure with a certain functional type from a compact storage (flat) configuration. Kirigami can effectively provide new ideas and solutions for the design of deployable mechanisms. Saito et al. proposed a novel method to construct arbitrary cross-section composite honeycombs by changing the crease and cut pattern (<xref ref-type="bibr" rid="B11">Nojima and Saito, 2006</xref>; <xref ref-type="bibr" rid="B13">Saito et al., 2014</xref>). Broccolo et al. described the development, manufacturing, and testing of a zero Poisson&#x2019;s ratio cellular structure using kirigami-inspired techniques (<xref ref-type="bibr" rid="B1">Broccolo et al., 2017</xref>). Calisch et al. designed an algorithm for producing a processable cut-and-fold pattern from a three-dimensional volume (<xref ref-type="bibr" rid="B2">Calisch et al., 2018</xref>). Neville et al. presented a shape memory polymer honeycomb with tunable and shape-morphing mechanical characteristics (<xref ref-type="bibr" rid="B10">Neville et al., 2017</xref>). Lyu et al. developed a novel family of cellular mechanical metamaterials based on rigid-foldable square-twist origami (<xref ref-type="bibr" rid="B9">Lyu et al., 2021</xref>).</p>
<p>Inspired by the porous unit structure in kirigami, a novel deployable mechanism with a type-preserving feature is proposed in this paper. A parabolic cylindrical surface can be approximated not only at the fully deployed state but also at the intermediate state. Different Poisson&#x2019;s ratios of the mechanism can be realized by the design of a unit combination scheme.</p>
<p>In the following section, the introduction of the type-preserving feature is described. In <xref ref-type="sec" rid="s3">Section 3</xref>, the typical basic cells and units are presented; the construction of networks is undertaken to obtain different Poisson&#x2019;s ratios. Two geometric methods are proposed to obtain the parameters to approximate cylindrical surface. One method is specifically designed to approximate a parabolic cylindrical surface, while the other is suitable for approximate arbitrary cylindrical surface. In <xref ref-type="sec" rid="s4">Section 4</xref>, position analysis is performed and the type-preserving feature is proved. Three cases with different Poisson&#x2019;s ratios are performed and validated by simulations in <xref ref-type="sec" rid="s5">Section 5</xref>.</p>
</sec>
<sec id="s2">
<title>2 Type-preserving feature</title>
<p>
<xref ref-type="fig" rid="F1">Figure 1</xref> presents the three different configurations of a typical deployable mechanism, namely the folded, intermediate, and deployed configurations (<xref ref-type="bibr" rid="B16">Xiao et al., 2018</xref>). It can be easily transported and stored at the folded state. The mechanism in the fully deployed configuration can fit a cylindrical surface, which is usually utilized as the reflector of an antenna. Little attention had been paid to the intermediate configuration of the mechanism, since there is hardly any practical application value with its irregular outer contour.</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption>
<p>Configurations of a deployable mechanism.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g001.tif"/>
</fig>
<p>To fully use the deployable mechanism, it is desired that the mechanism in the intermediate configuration can have a working surface. A novel kirigami-inspired deployable mechanism, which has the feature of type preserving, is proposed in this paper. Herein, type preserving indicates that the fitted surfaces in the intermediate and deployed configurations are of the same type, for example both are parabolic cylindrical surfaces. Parameters of the fitting surface may change while the type of the surface remains the same.</p>
<p>An example of the proposed mechanism is shown in <xref ref-type="fig" rid="F2">Figure 2</xref>. From the side view, it can be found that the mechanism can approximate cylindrical surfaces whose directrix is a biquadratic curve. With the changing of deployable angles, coefficients of the directrix varies but the type of the curve is invariable.</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption>
<p>An example of a kirigami-inspired type-preserving mechanism.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g002.tif"/>
</fig>
</sec>
<sec id="s3">
<title>3 Construction of the deployable mechanism</title>
<p>The designed deployable mechanism is inspired by kirigami, which integrates both folding and cutting. The mechanism can be constructed from a flat sheet with creases and cuts. Three typical cells are selected for forming the basic units with different Poisson&#x2019;s ratios. Type-preserving networks based on the units are established to approximate parabolic cylindrical surfaces.</p>
<sec id="s3-1">
<title>3.1 Basic cells</title>
<p>Three typical basic cells, namely the hexagonal cell, the re-entrant hexagonal cell, and the semi re-entrant hexagonal cell, are adopted in the design of a type-preserving deployable mechanism in this study (<xref ref-type="bibr" rid="B6">Grima et al., 2010</xref>; <xref ref-type="bibr" rid="B7">Li et al., 2021</xref>). The cross-sections of the basic cells are illustrated in <xref ref-type="fig" rid="F3">Figure 3</xref>.</p>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption>
<p>Cross-sections of typical basic cells <bold>(A)</bold> Hexagonal cell <bold>(B)</bold> Re-entrant hexagonal cell <bold>(C)</bold> Semi re-entrant hexagonal cell.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g003.tif"/>
</fig>
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<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msubsup>
</mml:mrow>
</mml:math>
</inline-formula> , and <inline-formula id="inf9">
<mml:math id="m10">
<mml:mrow>
<mml:msubsup>
<mml:mi>l</mml:mi>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msubsup>
</mml:mrow>
</mml:math>
</inline-formula> is the length of the edge connecting two adjacent cells in the three cases, respectively.</p>
<p>The Poisson&#x2019;s ratio of cells is defined as<disp-formula id="e2">
<mml:math id="m11">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mi>v</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:mo>&#x2212;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b5;</mml:mi>
<mml:mi>x</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b5;</mml:mi>
<mml:mi>y</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(2)</label>
</disp-formula>
</p>
<p>Then for three different cells, the Poisson&#x2019;s ratio can be calculated as<disp-formula id="e3">
<mml:math id="m12">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="center">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>v</mml:mi>
<mml:mrow>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>tan</mml:mi>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>v</mml:mi>
<mml:mrow>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>tan</mml:mi>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>v</mml:mi>
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mn>0</mml:mn>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(3)</label>
</disp-formula>
</p>
<p>Here, if <italic>&#x3b8;</italic>&#x2208; [60&#xb0;, 160&#xb0;], then the variation of Poisson&#x2019;s ratio of cells with respect to the deployable angle <italic>&#x3b8;</italic> is shown in <xref ref-type="fig" rid="F4">Figure 4</xref>.</p>
<fig id="F4" position="float">
<label>FIGURE 4</label>
<caption>
<p>The variation of Poisson&#x2019;s ratio of cells with respect to the deployable angle <bold>(A)</bold> Hexagonal cell <bold>(B)</bold> Re-entrant hexagonal cell <bold>(C)</bold> Semi re-entrant hexagonal cell.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g004.tif"/>
</fig>
<p>As shown in <xref ref-type="fig" rid="F4">Figure 4</xref>, the hexagonal cell exhibits a positive Poisson&#x2019;s ratio, the re-entrant hexagonal cell displays a negative Poisson&#x2019;s ratio, and the semi re-entrant hexagonal cell has a zero Poisson&#x2019;s ratio. The distinct structural styles of these three basic cells lead to variations in their respective Poisson&#x2019;s ratios.</p>
<p>In the proposed design, the cells are 3D honeycomb structures. Kirigami is considered as an innovative and effective method for advanced three-dimensional fabrication through cutting and folding thin sheets. Inspired by kirigami, a novel single-layer-folding method is proposed to obtain the 3D cell from flat paper. The crease and cut patterns of the three basic cells are shown in <xref ref-type="fig" rid="F5">Figure 5</xref>. The structural parameters are illustrated in the figure. The solid and dotted lines represent the mount and valley creases, respectively. The sheet is cut along the bold lines.</p>
<fig id="F5" position="float">
<label>FIGURE 5</label>
<caption>
<p>The crease and cut patterns of the three basic cells <bold>(A)</bold> Hexagonal cell <bold>(B)</bold> Re-entrant hexagonal cell <bold>(C)</bold> Semi re-entrant hexagonal cell.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g005.tif"/>
</fig>
<p>According to the geometric constraints, parameters <italic>a</italic>, <italic>b</italic>, <italic>c</italic>, and <italic>D</italic> of the cells satisfy the following conditions<disp-formula id="e4">
<mml:math id="m13">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="center">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mo>&#x2264;</mml:mo>
<mml:mi>b</mml:mi>
<mml:mo>&#x2264;</mml:mo>
<mml:mi>c</mml:mi>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:mi>D</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>c</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>2</mml:mn>
<mml:mi>b</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:mfrac>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(4)</label>
</disp-formula>
</p>
<p>The folding process of the hexagonal cell is shown in <xref ref-type="fig" rid="F6">Figure 6</xref>. It is similar to the folding process of the re-entrant hexagonal cell and the semi re-entrant hexagonal cell.</p>
<fig id="F6" position="float">
<label>FIGURE 6</label>
<caption>
<p>The folding process of hexagonal cell.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g006.tif"/>
</fig>
<p>There is no need to stick the sheet using the single-layer-folding method, which makes it easy to obtain the deployable mechanism from a flat sheet. The proposed single-layer-folding method is suitable for small curvature directrix and sheets with a certain thickness.</p>
</sec>
<sec id="s3-2">
<title>3.2 Units with different Poisson&#x2019;s ratios</title>
<p>By combining the basic cells, three basic units with different Poisson&#x2019;s ratios are obtained. The unit with a positive Poisson&#x2019;s ratio is obtained by combining three hexagonal cells. Three re-entrant hexagonal cells are connected to get a negative Poisson&#x2019;s ratio unit. The zero Poisson&#x2019;s ratio unit is obtained by arranging the three basic cells, which is named the integrated unit. The three basic units, the corresponding crease, and the cut patterns are shown in <xref ref-type="fig" rid="F7">Figure 7</xref>. The left side of <xref ref-type="fig" rid="F7">Figure 7</xref> shows the top view of the three basic units. Black lines indicate that the unit is in the fully deployed configuration; the intermediate configuration of the unit is shown in red. The front view and axonometric view are shown in the middle. The crease and cut pattern of the three basic units is on the right side of <xref ref-type="fig" rid="F7">Figure 7</xref>.</p>
<fig id="F7" position="float">
<label>FIGURE 7</label>
<caption>
<p>Three basic units <bold>(A)</bold> Hexagonal unit <bold>(B)</bold> re-entrant hexagonal unit <bold>(C)</bold> integrated unit.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g007.tif"/>
</fig>
</sec>
<sec id="s3-3">
<title>3.3 Network of the basic units</title>
<p>The size of a unit is limited. Thus, the large-scale deployable mechanism should be constructed by networking the proposed units. Different deployable mechanisms with positive, negative, and zero Poisson&#x2019;s ratios are constructed with the three kinds of units.</p>
<p>It is assumed that the mechanism is in its fully deployed configuration when the deployable angle <italic>&#x3b8;</italic> is 120&#xb0;. As shown in <xref ref-type="fig" rid="F8">Figure 8A</xref>, in the first network, three hexagonal units with the same size but different colors are patterned along the horizontal and vertical directions. The Poisson&#x2019;s ratio of the mechanism is positive. Similarly, a mechanism with negative Poisson&#x2019;s ratio is obtained by networking the re-entrant hexagonal units, as shown in <xref ref-type="fig" rid="F8">Figure 8B</xref>.</p>
<fig id="F8" position="float">
<label>FIGURE 8</label>
<caption>
<p>Network of the basic units <bold>(A)</bold> Positive Poisson&#x2019;s ratio network <bold>(B)</bold> Negative Poisson&#x2019;s ratio network <bold>(C)</bold> Zero Poisson&#x2019;s ratio network <bold>(D)</bold> Another zero Poisson&#x2019;s ratio network.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g008.tif"/>
</fig>
<p>Two networking patterns are presented in <xref ref-type="fig" rid="F8">Figures 8C, D</xref> to obtain mechanisms with zero Poisson&#x2019;s ratio. <xref ref-type="fig" rid="F8">Figure 8C</xref> shows the tessellation of the integrated units; two magenta semi re-entrant hexagonal cells need to be added between two integrated units. Since the Poisson&#x2019;s ratio of this unit is zero, the composed mechanism is zero Poisson&#x2019;s ratio accordingly. In <xref ref-type="fig" rid="F8">Figure 8D</xref>, hexagonal units and re-entrant hexagonal units are patterned with the semi re-entrant hexagonal cells. Some parts of the mechanism are positive Poisson&#x2019;s ratio and other parts are negative Poisson&#x2019;s ratio. The Poisson&#x2019;s ratio of the whole mechanism is zero.</p>
</sec>
<sec id="s3-4">
<title>3.4 Geometric methods for approximating cylindrical surfaces</title>
<sec id="s3-4-1">
<title>3.4.1 Approximating parabolic cylindrical surface</title>
<p>Parabola has the advantage of gathering signals to its focus, and is widely used in antenna reflectors (<xref ref-type="bibr" rid="B17">Xiao et al., 2020</xref>). Based on the proposed deployable mechanism, continuous tangents are selected to fit the directrix of the parabolic cylindrical surface, as shown in <xref ref-type="fig" rid="F9">Figure 9</xref>. The points of tangent are exactly located on the parabola.</p>
<fig id="F9" position="float">
<label>FIGURE 9</label>
<caption>
<p>Approximation of parabolic cylindrical surface.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g009.tif"/>
</fig>
<p>The continuous tangents are the projection of the upper surface of each unit on the plumb surface. The horizontal length of the fitted tangent is the width of the projection of its corresponding unit on the plumb surface, which is denoted as <italic>w</italic>. Therefore, the <italic>x</italic>-coordinate of the first fitting point is <italic>w</italic>/2.</p>
<p>According to the geometric relationship between the tangent and parabola, the tangent slope <italic>k</italic> can be deduced as<disp-formula id="e5">
<mml:math id="m14">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mi>k</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mn>4</mml:mn>
<mml:mi>g</mml:mi>
<mml:msub>
<mml:mi>x</mml:mi>
<mml:mi>t</mml:mi>
</mml:msub>
<mml:mo>&#xb1;</mml:mo>
<mml:msqrt>
<mml:mrow>
<mml:mn>16</mml:mn>
<mml:msup>
<mml:mi>g</mml:mi>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:msubsup>
<mml:mi>x</mml:mi>
<mml:mi>t</mml:mi>
<mml:mn>2</mml:mn>
</mml:msubsup>
</mml:mrow>
</mml:msqrt>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:mfrac>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(5)</label>
</disp-formula>where <italic>g</italic> is the parabola coefficient and <italic>x</italic>
<sub>
<italic>t</italic>
</sub> represents the <italic>x</italic>-coordinate of the fitting point.</p>
<p>The intercept <italic>e</italic> of the tangent is<disp-formula id="e6">
<mml:math id="m15">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mi>e</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>y</mml:mi>
<mml:mi>t</mml:mi>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>g</mml:mi>
<mml:msub>
<mml:mi>x</mml:mi>
<mml:mi>t</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(6)</label>
</disp-formula>where <italic>y</italic>
<sub>
<italic>t</italic>
</sub> is the <italic>y</italic>-coordinate of the tangent point.</p>
<p>For a given parabola with the coefficient <italic>g</italic>, the expression of the tangent corresponding to the first fitting point can be obtained through Eqs <xref ref-type="disp-formula" rid="e5">5</xref>, <xref ref-type="disp-formula" rid="e6">6</xref>. Then, the coordinates of the next fitting point can be calculated similarly. By analogy, all the tangents and fitting points can be obtained.</p>
</sec>
<sec id="s3-4-2">
<title>3.4.2 Approximating arbitrary cylindrical surface</title>
<p>The fitting method for a cylindrical surface with an arbitrary curve as the directrix is different from the method of fitting a parabolic cylindrical surface mentioned above. Though the method is not as effective as the method for fitting parabolic cylindrical surfaces, it is also applicable. Taking a cylindrical surface with sine curve as the directrix, its approximation is shown in <xref ref-type="fig" rid="F10">Figure 10</xref>. In this method, continuous polylines are used to fit the directrix; the intersection point of two adjacent polylines is exactly located on the directrix. The continuous polylines are the projection of the upper surface of each unit on the plumb surface. The horizontal length of the fitted tangent is the width of the projection of its corresponding unit on the plumb surface, which is denoted as <italic>w</italic>. Therefore, the <italic>x</italic>-coordinate of the first fitting point <italic>P</italic>
<sub>1</sub> is 0.</p>
<fig id="F10" position="float">
<label>FIGURE 10</label>
<caption>
<p>Approximation of an arbitrary cylindrical surface.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g010.tif"/>
</fig>
<p>Therefore, when the function of the directrix is given as <italic>F</italic>(<italic>x</italic>), the <italic>x</italic> and <italic>z</italic> coordinates of the fitting point <italic>P</italic>
<sub>
<italic>i</italic>
</sub> can be obtained as<disp-formula id="e7">
<mml:math id="m16">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="center">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>w</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>F</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(7)</label>
</disp-formula>
</p>
</sec>
</sec>
</sec>
<sec id="s4">
<title>4 Kinematic analysis</title>
<p>In this section, the kinematic model of the proposed kirigami-inspired deployable mechanism is established. Based on the position analysis, the feature of type preserving of the mechanism has been analyzed. Since the two methods have different approximations for cylindrical surfaces, they are discussed separately.</p>
<sec id="s4-1">
<title>4.1 The method for approximating parabolic cylindrical surface</title>
<sec id="s4-1-1">
<title>4.1.1 Position analysis</title>
<p>As shown in <xref ref-type="fig" rid="F11">Figure 11</xref>, the coordinate system of the proposed deployable mechanism is established using the method for approximating parabolic cylindrical surfaces; the blue panels of the mechanism are always parallel to the plane <italic>O</italic>-<italic>YZ</italic>, while the red panels and green panels remain parallel to themselves, respectively. The origin <italic>O</italic> is located at the midpoint of the upper surface of the first unit of the mechanism. The lengths of the mechanism along the <italic>x</italic>-axis and <italic>y</italic>-axis change with the deployable angle <italic>&#x3b8;</italic>. To reduce the analysis complexity, the position analysis is decomposed into two parts, namely motions on the plane <italic>O</italic>-<italic>XZ</italic> and <italic>O</italic>-<italic>YZ</italic>, respectively.</p>
<fig id="F11" position="float">
<label>FIGURE 11</label>
<caption>
<p>Coordinate system of the kirigami-inspired deployable mechanism using the method for approximating parabolic cylindrical surfaces <bold>(A)</bold> Front view <bold>(B)</bold> End view <bold>(C)</bold> Vertical view <bold>(D)</bold> Axonometric view.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g011.tif"/>
</fig>
<p>
<xref ref-type="fig" rid="F12">Figure 12</xref> presents the view on <italic>O</italic>-<italic>XZ</italic> of the mechanism. <italic>L</italic>
<sub>
<italic>x</italic>
</sub> indicates the length along the <italic>x</italic>-axis of the designed mechanisms. It only relates to the number of cells along the <italic>x</italic>-axis and the value of <italic>&#x3b8;</italic>. The type of cell has no effect on <italic>L</italic>
<sub>
<italic>x</italic>
</sub>. Therefore, the <italic>L</italic>
<sub>
<italic>x</italic>
</sub> of the four networks in <xref ref-type="fig" rid="F7">Figure 7</xref> can be expressed as<disp-formula id="e8">
<mml:math id="m17">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>L</mml:mi>
<mml:mi>x</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mn>2</mml:mn>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mi>x</mml:mi>
</mml:msub>
<mml:msub>
<mml:mi>l</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mo>&#x2061;</mml:mo>
<mml:mi>sin</mml:mi>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(8)</label>
</disp-formula>where <italic>n</italic>
<sub>
<italic>x</italic>
</sub> is the number of cells along the <italic>x</italic>-axis. The length <italic>L</italic>
<sub>
<italic>x</italic>
</sub> declines when the deployable angle <italic>&#x3b8;</italic> decreases, namely it is compressed along the <italic>x</italic>-axis with the folding of the mechanism.</p>
<fig id="F12" position="float">
<label>FIGURE 12</label>
<caption>
<p>View on <italic>O</italic>-<italic>XZ</italic>.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g012.tif"/>
</fig>
<p>The slope of the tangent and coordinates of the fitting point vary with the change of <italic>&#x3b8;</italic>. According to the analysis of the basic cells and units, the slope <italic>k</italic>
<sub>
<italic>i</italic>
</sub> of the <italic>i</italic>th tangent is<disp-formula id="e9">
<mml:math id="m18">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>k</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mn>2</mml:mn>
<mml:mi>g</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:msub>
<mml:mi>l</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mfrac>
<mml:mrow>
<mml:msup>
<mml:mi>sin</mml:mi>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(9)</label>
</disp-formula>where <italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub> is the deployable angle at the fully deployed configuration.</p>
<p>The coordinates of point <italic>P</italic>
<sub>
<italic>i</italic>
</sub> can be obtained as<disp-formula id="e10">
<mml:math id="m19">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="center">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mn>3</mml:mn>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:msub>
<mml:mi>l</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mo>&#x2061;</mml:mo>
<mml:mi>sin</mml:mi>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>h</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(10)</label>
</disp-formula>where <italic>P</italic>
<sub>
<italic>ix</italic>
</sub> and <italic>P</italic>
<sub>
<italic>iz</italic>
</sub> represent the <italic>x</italic> and <italic>z</italic> coordinates of the point <italic>P</italic>
<sub>
<italic>i</italic>
</sub>; hi denotes the height of the corresponding cell.</p>
<p>The length <italic>L</italic>
<sub>
<italic>y</italic>
</sub> along the <italic>y</italic>-axis of the mechanism is determined by the number of cells, cell types, and the deployable angle. The number of positive Poisson&#x2019;s ratio cells, negative Poisson&#x2019;s ratio cells, and zero Poisson&#x2019;s ratio cells along the <italic>y</italic>-axis is denoted as <italic>n</italic>
<sub>
<italic>hex</italic>
</sub>, <italic>n</italic>
<sub>
<italic>r-hex,</italic>
</sub> and <italic>n</italic>
<sub>
<italic>s-r-hex</italic>
</sub>, respectively. The length <italic>L</italic>
<sub>
<italic>y</italic>
</sub> can be derived as<disp-formula id="e11">
<mml:math id="m20">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>L</mml:mi>
<mml:mi>y</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>L</mml:mi>
<mml:mi>&#x3b8;</mml:mi>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:msub>
<mml:mi>L</mml:mi>
<mml:mi>s</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(11)</label>
</disp-formula>where<disp-formula id="e12">
<mml:math id="m21">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="left">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>L</mml:mi>
<mml:mi>&#x3b8;</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mrow>
<mml:mfenced open="[" close="]" separators="|">
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mi>cos</mml:mi>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mi>l</mml:mi>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>L</mml:mi>
<mml:mi>s</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>2</mml:mn>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>3</mml:mn>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:msub>
<mml:mi>l</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mo>&#x2b;</mml:mo>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:msubsup>
<mml:mi>l</mml:mi>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msubsup>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>2</mml:mn>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:msubsup>
<mml:mi>l</mml:mi>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msubsup>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>3</mml:mn>
<mml:msub>
<mml:mi>n</mml:mi>
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:msubsup>
<mml:mi>l</mml:mi>
<mml:mn>2</mml:mn>
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>r</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>h</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msubsup>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(12)</label>
</disp-formula>where <italic>L</italic>
<sub>
<italic>&#x3b8;</italic>
</sub> is the sum of the lengths projected on the <italic>y</italic>-axis by edges that are not parallel to the <italic>y</italic>-axis; <italic>L</italic>
<sub>
<italic>s</italic>
</sub> is the sum of the lengths projected on the <italic>y</italic>-axis by edges that are parallel to the <italic>y</italic>-axis. <italic>L</italic>
<sub>
<italic>&#x3b8;</italic>
</sub> varies with the deployable angle <italic>&#x3b8;</italic>; <italic>L</italic>
<sub>
<italic>s</italic>
</sub> is constant during the deployment of the mechanism.</p>
<p>
<italic>L</italic>
<sub>
<italic>&#x3b8;</italic>
</sub> &#x3d; 0 when the number of positive Poisson&#x2019;s ratio cells is equal to the number of negative Poisson&#x2019;s ratio cells along the <italic>y</italic>-axis. In this case, the length <italic>L</italic>
<sub>
<italic>y</italic>
</sub> of the mechanism will not change when the deployable angle varies, which illustrates that the Poisson&#x2019;s ratio of the mechanism is zero. It can be seen that the networks of units in <xref ref-type="fig" rid="F6">Figures 6C, D</xref> satisfy the condition. Similarly, the mechanism will show positive Poisson&#x2019;s ratio if the number of positive Poisson&#x2019;s ratio cells are more than the number of negative Poisson&#x2019;s ratio cells along the <italic>y</italic>-axis. On the contrary, the mechanism shows the characteristic of negative Poisson&#x2019;s ratio.</p>
</sec>
<sec id="s4-1-2">
<title>4.1.2 Analysis of type-preserving feature</title>
<p>
<xref ref-type="fig" rid="F13">Figure 13</xref> presents the <italic>i</italic>th tangent of the mechanism at the deployed and intermediate states. The corresponding coordinates of these points and the slope of the tangent can be obtained with the above analysis.</p>
<fig id="F13" position="float">
<label>FIGURE 13</label>
<caption>
<p>The <italic>i</italic>-th tangent at the deployed and intermediate states.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g013.tif"/>
</fig>
<p>The relationship between the coordinates of <italic>T</italic>
<sub>
<italic>i</italic>
</sub> and <italic>T</italic>
<sub>
<italic>i</italic>
</sub>
<sup>d</sup> can be expressed as<disp-formula id="e13">
<mml:math id="m22">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="center">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(13)</label>
</disp-formula>
</p>
<p>The tangent point <italic>T</italic>
<sub>
<italic>i</italic>
</sub>
<sup>d</sup> is located on the fitting parabola. It can be derived as<disp-formula id="e14">
<mml:math id="m23">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>g</mml:mi>
<mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>e</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>g</mml:mi>
<mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>e</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>g</mml:mi>
<mml:mi>m</mml:mi>
</mml:msub>
<mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>e</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(14)</label>
</disp-formula>where<disp-formula id="e15">
<mml:math id="m24">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>g</mml:mi>
<mml:mi>m</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>g</mml:mi>
<mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(15)</label>
</disp-formula>
</p>
<p>Thus, the relationship between the <italic>x</italic> and <italic>z</italic> coordinates of <italic>T</italic>
<sub>
<italic>i</italic>
</sub> is<disp-formula id="e16">
<mml:math id="m25">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>g</mml:mi>
<mml:mi>m</mml:mi>
</mml:msub>
<mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>e</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(16)</label>
</disp-formula>which means the tangent point <italic>T</italic>
<sub>
<italic>i</italic>
</sub> at the intermediate state is located at the parabola <italic>z</italic> &#x3d; <italic>g</italic>
<sub>
<italic>m</italic>
</sub>
<italic>x</italic> &#x2b;<italic>e</italic>.</p>
<p>The slope of a line, which is tangential to the parabola at the point <italic>T</italic>
<sub>
<italic>i</italic>
</sub>, can be calculated with the parabola coefficient <italic>g</italic>
<sub>
<italic>m</italic>
</sub> and the coordinates of the point <italic>T</italic>
<sub>
<italic>i</italic>
</sub>. The slope is<disp-formula id="e17">
<mml:math id="m26">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>k</mml:mi>
<mml:mi>m</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mn>2</mml:mn>
<mml:mi>g</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:msub>
<mml:mi>l</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mfrac>
<mml:mrow>
<mml:msup>
<mml:mi>sin</mml:mi>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(17)</label>
</disp-formula>which is consistent with that derived in Eq. <xref ref-type="disp-formula" rid="e9">9</xref>.</p>
<p>Therefore, the mechanism is able to approximate a parabolic cylindrical surface at the intermediate state, which confirms the type-preserving feature of the mechanism.</p>
</sec>
</sec>
<sec id="s4-2">
<title>4.2 The method for approximating arbitrary cylindrical surface</title>
<sec id="s4-2-1">
<title>4.2.1 Position analysis</title>
<p>As shown in <xref ref-type="fig" rid="F14">Figure 14</xref>, the coordinate system of the proposed deployable mechanism is established using the method for approximating an arbitrary cylindrical surface; the blue panels of the mechanism are always parallel to the plane <italic>O</italic>-<italic>YZ</italic>. The origin <italic>O</italic> is located at the lower surface of the first unit of the mechanism. The lengths of the mechanism along the <italic>x</italic>-axis and <italic>y</italic>-axis also change with the deployable angle <italic>&#x3b8;</italic>. The position analysis is decomposed into two parts to reduce the analysis complexity, namely motions on the plane <italic>O</italic>-<italic>XZ</italic> and <italic>O</italic>-<italic>YZ</italic>, respectively.</p>
<fig id="F14" position="float">
<label>FIGURE 14</label>
<caption>
<p>Coordinate system of the mechanism using the method for approximating an arbitrary cylindrical surface <bold>(A)</bold> Front view <bold>(B)</bold> End view <bold>(C)</bold> Vertical view <bold>(D)</bold> Axonometric view.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g014.tif"/>
</fig>
<p>
<xref ref-type="fig" rid="F14">Figure 14C</xref> shows the vertical view of the mechanism; <italic>L</italic>
<sub>
<italic>x</italic>
</sub> and <italic>L</italic>
<sub>
<italic>y</italic>
</sub> indicates the length along the <italic>x</italic>-axis and <italic>y</italic>-axis of the designed mechanisms, respectively. The length <italic>L</italic>
<sub>
<italic>x</italic>
</sub> and <italic>L</italic>
<sub>
<italic>y</italic>
</sub> can be obtained through Eqs <xref ref-type="disp-formula" rid="e8">8</xref>, <xref ref-type="disp-formula" rid="e11">11</xref>, <xref ref-type="disp-formula" rid="e12">12</xref>.</p>
<p>In addition, the Poisson&#x2019;s ratio properties of this mechanism are the same as those of the mechanism approximating parabolic cylindrical surface.</p>
</sec>
<sec id="s4-2-2">
<title>4.2.2 Analysis of type-preserving feature</title>
<p>The fitting points <italic>P</italic>
<sub>
<italic>i</italic>
</sub> and <italic>P</italic>
<sub>
<italic>i&#x2b;1</italic>
</sub> of the mechanism at the deployed and intermediate states are shown in <xref ref-type="fig" rid="F15">Figure 15</xref>. The corresponding coordinates of these points and the slope of the tangent can be obtained with the above analysis.</p>
<fig id="F15" position="float">
<label>FIGURE 15</label>
<caption>
<p>The fitting points <italic>P</italic>
<sub>
<italic>i</italic>
</sub> and <italic>P</italic>
<sub>
<italic>i&#x2b;1</italic>
</sub> of the mechanism at the deployed and intermediate states.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g015.tif"/>
</fig>
<p>The relationship between the coordinates of the fitting points <italic>P</italic>
<sub>
<italic>i</italic>
</sub> and <italic>P</italic>
<sub>
<italic>i</italic>
</sub>
<sup>
<italic>d</italic>
</sup> can be expressed as<disp-formula id="e18">
<mml:math id="m27">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mfenced open="{" close="" separators="|">
<mml:mrow>
<mml:mtable columnalign="center">
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(18)</label>
</disp-formula>
</p>
<p>The fitting point <italic>P</italic>
<sub>
<italic>i</italic>
</sub>
<sup>d</sup> is located on the fitting cylindrical surface at the intermediate state. It can be derived as<disp-formula id="e19">
<mml:math id="m28">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(19)</label>
</disp-formula>where <italic>G</italic> (<italic>x</italic>) is the function for the directrix of the fitting cylindrical surface at the intermediate state, it can be represented as<disp-formula id="e20">
<mml:math id="m29">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mi>G</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>F</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(20)</label>
</disp-formula>
</p>
<p>Thus, combining with Eq. <xref ref-type="disp-formula" rid="e17">17</xref>, it can be obtained that<disp-formula id="e21">
<mml:math id="m30">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>F</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
<mml:mi>d</mml:mi>
</mml:msubsup>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>F</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>z</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(21)</label>
</disp-formula>
</p>
<p>Therefore, the mechanism is able to approximate the same type of cylindrical surface at the intermediate state, which confirms the type-preserving feature of the mechanism.</p>
</sec>
</sec>
</sec>
<sec id="s5">
<title>5 Case studies</title>
<p>In this section, three case studies are investigated. Kirigami-inspired deployable mechanisms with positive, negative, and zero Poisson&#x2019;s ratios are presented, respectively.</p>
<sec id="s5-1">
<title>5.1 Case I</title>
<p>The Poisson&#x2019;s ratio of the network in this case is positive. The mechanism, which can approximate a parabolic cylindrical surface, is composed of the hexagonal units. Parameters of this case are presented in <xref ref-type="table" rid="T1">Table 1</xref>.</p>
<table-wrap id="T1" position="float">
<label>TABLE 1</label>
<caption>
<p>The parameters of case I.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">Parabolic Coefficients/<italic>g</italic>
</th>
<th align="center">Cell initial angle/<italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub>
</th>
<th align="center">Number of units along <italic>y</italic>-axis/<italic>n</italic>
</th>
<th align="center">Fitting range/cm</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">0.1</td>
<td align="center">120&#xb0;</td>
<td align="center">4</td>
<td align="center">
<italic>x</italic>&#x2208; [0,6]</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>The length <italic>l</italic>
<sub>1</sub> of the cells mainly depends on processing requirements and structural strength. Since these two are not relevant in this case, the length <italic>l</italic>
<sub>1</sub> is set to 1&#xa0;cm. The parameters of each cell are calculated using the method proposed in <xref ref-type="sec" rid="s4-1">Section 4.1</xref>, as shown in <xref ref-type="table" rid="T2">Table 2</xref>.</p>
<table-wrap id="T2" position="float">
<label>TABLE 2</label>
<caption>
<p>The parameters of each cell of case I.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">Cell number</th>
<th align="center">
<italic>a</italic>/cm</th>
<th align="center">
<italic>b</italic>/cm</th>
<th align="center">
<italic>c</italic>/cm</th>
<th align="center">
<italic>D</italic>/cm</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">1</td>
<td align="center">1.000</td>
<td align="center">1.000</td>
<td align="center">1.150</td>
<td align="center">0.075</td>
</tr>
<tr>
<td align="center">2</td>
<td align="center">1.150</td>
<td align="center">1.450</td>
<td align="center">1.900</td>
<td align="center">0.075</td>
</tr>
<tr>
<td align="center">3</td>
<td align="center">1.900</td>
<td align="center">2.500</td>
<td align="center">3.250</td>
<td align="center">0.075</td>
</tr>
<tr>
<td align="center">4</td>
<td align="center">3.250</td>
<td align="center">4.150</td>
<td align="center">5.200</td>
<td align="center">0.075</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>The crease and cut patterns are displayed in <xref ref-type="fig" rid="F16">Figure 16</xref>. The single-layer folding method is applied to fabricate the deployable mechanism.</p>
</fn>
</table-wrap-foot>
</table-wrap>
<fig id="F16" position="float">
<label>FIGURE 16</label>
<caption>
<p>Crease and cut patterns of case I.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g016.tif"/>
</fig>
<p>The obtained kirigami-inspired deployable mechanism is shown in <xref ref-type="fig" rid="F17">Figure 17</xref>. The number of cells along the <italic>y</italic>-axis is 4. The mechanism is fully deployed when the deployed angle is 120&#xb0;. The fitting parabola is <italic>y</italic> &#x3d; <italic>x</italic>
<sup>2</sup>/10 corresponding to <italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub> &#x3d; 120&#xb0;.</p>
<fig id="F17" position="float">
<label>FIGURE 17</label>
<caption>
<p>The kirigami-inspired deployable mechanism of case I.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g017.tif"/>
</fig>
<p>The coefficient of the fitting parabola varies from 0.100 to 0.228 with the changing of the deployable angle <italic>&#x3b8;</italic> from 120&#xb0; to 70&#xb0;. <xref ref-type="fig" rid="F18">Figure 18</xref> shows the fitting parabolas corresponding to different deployable angles. The mechanism can approximate different cylindrical surfaces with different <italic>&#x3b8;</italic>.</p>
<fig id="F18" position="float">
<label>FIGURE 18</label>
<caption>
<p>The fitted parabola corresponding to <italic>&#x3b8;</italic>.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g018.tif"/>
</fig>
<p>The Poisson&#x2019;s ratio of this case can be calculated through the kinematic analysis. The variation of Poisson&#x2019;s ratio with the deployable angle is displayed in <xref ref-type="fig" rid="F19">Figure 19</xref>, which is always positive.</p>
<fig id="F19" position="float">
<label>FIGURE 19</label>
<caption>
<p>Variation of Poisson&#x2019;s ratio of case I.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g019.tif"/>
</fig>
</sec>
<sec id="s5-2">
<title>5.2 Case II</title>
<p>The Poisson&#x2019;s ratio of the network in this case is negative. Parameters of this case are the same as those in Case I. The crease and cut patterns are presented in <xref ref-type="fig" rid="F20">Figure 20A</xref>. The single-layer folding method is applied to make the deployable mechanism.</p>
<fig id="F20" position="float">
<label>FIGURE 20</label>
<caption>
<p>Case II with negative Poisson&#x2019;s ratio <bold>(A)</bold> Crease and cut patterns <bold>(B)</bold> Axonometric view <bold>(C)</bold> Change of Poisson&#x2019;s ratio.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g020.tif"/>
</fig>
<p>
<xref ref-type="fig" rid="F20">Figure 20B</xref> shows the structure of the deployable mechanism. The mechanism is composed of the re-entrant hexagonal units. The number of cells along the <italic>y</italic>-axis is 4. At the fully deployed state, namely <italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub> &#x3d; 120&#xb0;, the function of the approximated parabola is <italic>z</italic> &#x3d; 0.1<italic>x</italic> (<xref ref-type="bibr" rid="B4">Ding et al., 2020</xref>). The mechanism can fit different parabolic cylindrical surfaces at the intermediate states.</p>
<p>
<xref ref-type="fig" rid="F20">Figure 20C</xref> displays the variation of the Poisson&#x2019;s ratio with the deployable angle. The Poisson&#x2019;s ratio of the mechanism is always negative, namely the length <italic>L</italic>
<sub>
<italic>y</italic>
</sub> declines with the decreasing of <italic>L</italic>
<sub>
<italic>x</italic>
</sub>. The configurations and approximated parabolic surfaces of the mechanism when <italic>&#x3b8;</italic> &#x3d; 120&#xb0; or <italic>&#x3b8;</italic> &#x3d; 50&#xb0; are shown in <xref ref-type="fig" rid="F21">Figure 21</xref>.</p>
<fig id="F21" position="float">
<label>FIGURE 21</label>
<caption>
<p>The kirigami-inspired deployable mechanism of case II <bold>(A)</bold> Fully deployed configuration <bold>(B)</bold> Intermediate configuration.</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g021.tif"/>
</fig>
</sec>
<sec id="s5-3">
<title>5.3 Case III</title>
<p>The proposed kirigami-inspired mechanism in this case is presented in <xref ref-type="fig" rid="F22">Figure 22</xref>. The network consists of the three kinds of basic cells. The fitting surface of the mechanism is always a parabolic cylinder. The Poisson&#x2019;s ratio of the mechanism is zero, i.e. <italic>L</italic>
<sub>
<italic>y</italic>
</sub> remains the same when the mechanism deploys or folds.</p>
<fig id="F22" position="float">
<label>FIGURE 22</label>
<caption>
<p>Case III with zero Poisson&#x2019;s ratio <bold>(A)</bold> Axonometric view (<italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub> &#x3d; 120&#xb0;) <bold>(B)</bold> Top view (<italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub> &#x3d; 120&#xb0;) <bold>(C)</bold> Front view (<italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub> &#x3d; 120&#xb0;) <bold>(D)</bold> Axonometric view (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;) <bold>(E)</bold> Top view (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;) <bold>(F)</bold> Front view (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;).</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g022.tif"/>
</fig>
<p>The <italic>X</italic> and <italic>Z</italic> coordinates of the fitting points (red dots) circle in the red and the <italic>Z</italic> coordinates of the fitted parabolic cylindrical surface under the corresponding <italic>X</italic> coordinate are illustrated in <xref ref-type="table" rid="T3">Tables 3</xref>, <xref ref-type="table" rid="T4">4</xref>. The fitted directrix are <italic>z</italic> &#x3d; 0.1000<italic>x</italic>
<sup>2</sup> &#x2b; 1 and <italic>z</italic> &#x3d; 0.4199<italic>x</italic>
<sup>2</sup>&#x2b;1&#xa0;at <italic>&#x3b8;</italic> &#x3d; 120&#xb0; and <italic>&#x3b8;</italic> &#x3d; 50&#xb0;, respectively. These fitting points are numbered from left to right. During the deploying process, the fitting points are always on the fitted directrix.</p>
<table-wrap id="T3" position="float">
<label>TABLE 3</label>
<caption>
<p>The <italic>X</italic> and <italic>Z</italic> coordinates of fitting points surrounded by a red circle in case III (<italic>&#x3b8;</italic> &#x3d; 120&#xb0;).</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">Point</th>
<th align="center">1</th>
<th align="center">2</th>
<th align="center">3</th>
<th align="center">4</th>
<th align="center">5</th>
<th align="center">6</th>
<th align="center">7</th>
<th align="center">8</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">
<italic>x</italic>(<italic>&#x3b8;</italic> &#x3d; 120&#xb0;)</td>
<td align="center">0.0000</td>
<td align="center">0.8660</td>
<td align="center">1.7320</td>
<td align="center">2.5981</td>
<td align="center">3.4641</td>
<td align="center">4.3301</td>
<td align="center">5.1962</td>
<td align="center">6.0622</td>
</tr>
<tr>
<td align="center">
<italic>z</italic>(<italic>&#x3b8;</italic> &#x3d; 120&#xb0;)</td>
<td align="center">1.0000</td>
<td align="center">1.0750</td>
<td align="center">1.3000</td>
<td align="center">1.6750</td>
<td align="center">2.2000</td>
<td align="center">2.8750</td>
<td align="center">3.7000</td>
<td align="center">4.6750</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T4" position="float">
<label>TABLE 4</label>
<caption>
<p>The <italic>X</italic> and <italic>Z</italic> coordinates of fitting points surrounded by a red circle of case III (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;).</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">Point</th>
<th align="center">1</th>
<th align="center">2</th>
<th align="center">3</th>
<th align="center">4</th>
<th align="center">5</th>
<th align="center">6</th>
<th align="center">7</th>
<th align="center">8</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">
<italic>x</italic>(<italic>&#x3b8;</italic> &#x3d; 50&#xb0;)</td>
<td align="center">0.0000</td>
<td align="center">0.4226</td>
<td align="center">0.8452</td>
<td align="center">1.2678</td>
<td align="center">1.6904</td>
<td align="center">2.1130</td>
<td align="center">2.5357</td>
<td align="center">2.9583</td>
</tr>
<tr>
<td align="center">
<italic>z</italic>(<italic>&#x3b8;</italic> &#x3d; 50&#xb0;)</td>
<td align="center">1.0000</td>
<td align="center">1.0750</td>
<td align="center">1.3000</td>
<td align="center">1.6750</td>
<td align="center">2.2000</td>
<td align="center">2.8750</td>
<td align="center">3.7000</td>
<td align="center">4.6750</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
<sec id="s5-4">
<title>5.4 Case IV</title>
<p>The Poisson&#x2019;s ratio of the network in this case is zero. The mechanism can approximate a cylindrical surface with sine curve as the directrix. Parameters of this case are presented in <xref ref-type="table" rid="T5">Table 5</xref>.</p>
<table-wrap id="T5" position="float">
<label>TABLE 5</label>
<caption>
<p>The parameters of case IV.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">
<italic>F</italic> (<italic>x</italic>)</th>
<th align="center">Cell initial angle/<italic>&#x3b8;</italic>
<sub>
<italic>d</italic>
</sub>
</th>
<th align="center">Number of units along y-axis/<italic>n</italic>
</th>
<th align="center">Fitting range/cm</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">
<italic>z</italic> &#x3d; sin(<italic>x</italic>)&#x2b;1.5</td>
<td align="center">120&#xb0;</td>
<td align="center">2</td>
<td align="center">
<italic>x</italic>&#x2208;[0,2&#x3c0;]</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>The proposed kirigami-inspired mechanism in this case is presented in <xref ref-type="fig" rid="F23">Figure 23</xref>. The network is the same as case III. The fitting surface of the mechanism is always a cylindrical surface with sine curve as the directrix. The Poisson&#x2019;s ratio of the mechanism is zero, i.e. <italic>L</italic>
<sub>
<italic>y</italic>
</sub> remains the same when the mechanism deploys or folds.</p>
<fig id="F23" position="float">
<label>FIGURE 23</label>
<caption>
<p>Case IV with zero Poisson&#x2019;s ratio <bold>(A)</bold> Axonometric view (<italic>&#x3b8;</italic> &#x3d; 120&#xb0;) <bold>(B)</bold> Top view (<italic>&#x3b8;</italic> &#x3d; 120&#xb0;) <bold>(C)</bold> Axonometric view (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;) <bold>(D)</bold> Top view (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;).</p>
</caption>
<graphic xlink:href="fmech-09-1225682-g023.tif"/>
</fig>
<p>According to Eq. <xref ref-type="disp-formula" rid="e18">18</xref>, <italic>G</italic> (<italic>x</italic>) can be represented as<disp-formula id="e22">
<mml:math id="m31">
<mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mi>G</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3b8;</mml:mi>
<mml:mi>d</mml:mi>
</mml:msub>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mi>sin</mml:mi>
<mml:mrow>
<mml:mfenced open="(" close=")" separators="|">
<mml:mrow>
<mml:mi>&#x3b8;</mml:mi>
<mml:mo>/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>1.5</mml:mn>
</mml:mrow>
</mml:mrow>
</mml:mrow>
</mml:math>
<label>(22)</label>
</disp-formula>
</p>
<p>The <italic>X</italic> and <italic>Z</italic> coordinates of the fitting points (red dots) and the <italic>Z</italic> coordinates of the fitted parabolic cylindrical surface under the corresponding <italic>X</italic> coordinate are illustrated in <xref ref-type="table" rid="T6">Tables 6</xref>, <xref ref-type="table" rid="T7">7</xref>. The fitted directrix are <italic>F</italic> (<italic>x</italic>) and <italic>G</italic> (<italic>x</italic>) at <italic>&#x3b8;</italic> &#x3d; 120&#xb0; and <italic>&#x3b8;</italic> &#x3d; 50&#xb0;, respectively. These fitting points are numbered from left to right. During the deploying process, the fitting points are always on the fitted directrix.</p>
<table-wrap id="T6" position="float">
<label>TABLE 6</label>
<caption>
<p>The <italic>X</italic> and <italic>Z</italic> coordinates of fitting points in case &#x2163; (<italic>&#x3b8;</italic> &#x3d; 120&#xb0;).</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">Point</th>
<th align="center">1</th>
<th align="center">2</th>
<th align="center">3</th>
<th align="center">4</th>
<th align="center">5</th>
<th align="center">6</th>
<th align="center">7</th>
<th align="center">8</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">
<italic>P</italic>
<sub>
<italic>ix</italic>
</sub> (<italic>&#x3b8;</italic> &#x3d; 120&#xb0;)</td>
<td align="center">0.0000</td>
<td align="center">0.5236</td>
<td align="center">1.0472</td>
<td align="center">1.5708</td>
<td align="center">2.0944</td>
<td align="center">2.6180</td>
<td align="center">3.1416</td>
<td align="center">3.6652</td>
</tr>
<tr>
<td align="center">
<italic>P</italic>
<sub>
<italic>iz</italic>
</sub> (<italic>&#x3b8;</italic> &#x3d; 120&#xb0;)</td>
<td align="center">1.5000</td>
<td align="center">2.0000</td>
<td align="center">2.3660</td>
<td align="center">2.5000</td>
<td align="center">2.3660</td>
<td align="center">2.0000</td>
<td align="center">1.5000</td>
<td align="center">1.0000</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T7" position="float">
<label>TABLE 7</label>
<caption>
<p>The <italic>X</italic> and <italic>Z</italic> coordinates of fitting points of case &#x2163; (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;).</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="center">Point</th>
<th align="center">1</th>
<th align="center">2</th>
<th align="center">3</th>
<th align="center">4</th>
<th align="center">5</th>
<th align="center">6</th>
<th align="center">7</th>
<th align="center">8</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="center">
<italic>P</italic>
<sub>
<italic>ix</italic>
</sub> (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;)</td>
<td align="center">0.0000</td>
<td align="center">0.2555</td>
<td align="center">0.5110</td>
<td align="center">0.7665</td>
<td align="center">1.0221</td>
<td align="center">1.2776</td>
<td align="center">1.5331</td>
<td align="center">1.7886</td>
</tr>
<tr>
<td align="center">
<italic>P</italic>
<sub>
<italic>iz</italic>
</sub> (<italic>&#x3b8;</italic> &#x3d; 50&#xb0;)</td>
<td align="center">1.5000</td>
<td align="center">2.0000</td>
<td align="center">2.3660</td>
<td align="center">2.5000</td>
<td align="center">2.3660</td>
<td align="center">2.0000</td>
<td align="center">1.5000</td>
<td align="center">1.0000</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
</sec>
<sec sec-type="conclusion" id="s6">
<title>6 Conclusion</title>
<p>A novel kirigami-inspired deployable mechanism with a type-preserving feature and controllable Poisson&#x2019;s ratio is proposed in this paper. Three basic cells with different Poisson&#x2019;s ratios, e.g., the hexagonal cell, re-entrant hexagonal cell, and semi re-entrant hexagonal cell, are presented and studied. The single-layer-folding method is utilized to obtain the 3D cell from flat paper. Deployable mechanisms with positive, negative, and zero Poisson&#x2019;s ratios are obtained by the network of the basic units. Two geometric methods are proposed to obtain the parameters to approximate a cylindrical surface. One method is specifically designed to approximate parabolic cylindrical surfaces, while the other is suitable for approximating arbitrary cylindrical surfaces. Kinematic analysis of the mechanism is performed. The characteristic of type preserving is proved, which illustrates the mechanism can fit an arbitrary cylindrical surface not only at the fully deployed state but also at the intermediate state. Four cases with different Poisson&#x2019;s ratios are performed and simulations are conducted to verify the feasibility of the design and analysis. The main advantages of the proposed mechanism are type-preserving and controllable Poisson&#x2019;s ratio, which makes it well-suited for deployment on commercial satellites that undergo constant mission variations. In future research, the incorporation of thick-panel origami can be considered in the design of mechanisms. Furthermore, exploring the development of simple drive systems for such mechanisms would also be a promising avenue for further investigation.</p>
</sec>
</body>
<back>
<sec sec-type="data-availability" id="s7">
<title>Data availability statement</title>
<p>The raw data supporting the conclusion of this article will be made available by the authors, without undue reservation.</p>
</sec>
<sec id="s8">
<title>Author contributions</title>
<p>JW: data curation, formal analysis, investigation, methodology, software, visualization, writing-original draft; HX: supervision, writing-review and editing; XD: funding acquisition, project administration, resources; SL: conceptualization, funding acquisition, validation, writing&#x2014;review and editing. All authors contributed to the article and approved the submitted version.</p>
</sec>
<sec id="s9">
<title>Funding</title>
<p>This work has been supported by the National Natural Science Foundation of China (Grant Nos 52075016, 52222501, 52105004, and 52192632) and the State Key Laboratory of Robotics and Systems (HIT) under Grant SKLRS-2022-KF-02.</p>
</sec>
<sec sec-type="COI-statement" id="s10">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec sec-type="disclaimer" id="s11">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
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