The present volume on materials and models with negative Poisson's ratio, called auxetics, and other systems with “negative” characteristics is the fourteenth focus issue of physica status solidi (b) on this subject.^[1^] The volume contains twenty four papers. Twenty one of them, on auxetic materials and models, are grouped in three sections: three‐dimensional (3D) auxetics, quasi‐two‐dimensional (Q2D) auxetics, and two‐dimensional (2D) auxetics. The remaining papers concern other systems with “negative” characteristics.

The section on 3D auxetics starts with effects of squeeze‐twist coupling, which were observed by Jianheng Li, Chan Soo Ha, and Roderic S. Lakes in chiral 3D isotropic lattices. Their paper ‘Observation of Squeeze‐Twist Coupling in a Chiral 3D Isotropic Lattice’ ^[2^] shows some very interesting results on experimental samples of the lattices, also benchmarked by previous Finite Element (FE) results. The authors apply Cosserat theory not only to validate the near‐zero Poisson's ratio measured using video‐gauge extensometry and Digital Image Correlation, but also to show the size‐dependence of Poisson's ratio for which a negative value is anticipated for a sufficient number of cells.

In the work ‘Response of Chiral Auxetic Composite Sandwich Panel to Fragment Simulating Projectile Impact’ by Nejc Novak et al.,^[3^] three‐dimensional chiral lattices were used as cores in sandwich panels subjected to ballistic impact. The cores were produced via selective electron beam melting from an alloy powder and joined with aluminium alloy plates. The auxetic cores and the plates were tested under quasi‐static and large strain rates using compression and tension. Very good correlation was observed between explicit FE simulations and the experimental results. The sandwich panels and plates separately were then subjected to ballistic impact (numerical and experimental). The presence of the core decreased significantly the velocity of the projectile passing through the panel. Simulations showed also that the change of the porosity of the auxetic core did not influence the global deformation response of the panel. These data may be of interest to the blast mitigation community.

In a very interesting article ‘Implications for Auxetic Response in Liquid Crystalline Polymers: X‐Ray Scattering and Space‐Filling Molecular Modeling’ by Prateek Verma, Chaobin He, and Anselm C. Griffin,^[4^] the authors give a very detailed and critical discussion of salient results from decades of work on auxetic liquid crystalline polymers led by Professor Anselm Griffin, an academic whose name has become very strongly associated with the chemistry of auxetics. Importantly, the authors provide some significant insights how the work could best proceed.

The last article in this section is ‘The Influence of the Soft Yukawa Potential and Hard Core Interactions on Auxeticity of the Face Centered Cubic Crystal of Hard‐Core Repulsive Yukawa Particles’ by Konstantin V. Tretiakov and Krzysztof W. Wojciechowski.^[5^] Those authors studied elastic properties and Poisson's ratio of the face centred cubic phases of three systems of particles which interact, respectively, with the hard sphere potential, the repulsive Yukawa potential, and the hard‐core repulsive Yukawa potential (HCRYP) which is composed of the previous two potentials. Results of the Monte Carlo simulations in the isobaric‐isothermal ensemble were compared in a broad range of pressures between melting and close packing for all the systems. Partial auxeticity was observed in each of them and the role of the hard and soft potentials, incorporated in HCRYP, was revealed. This study confirmed intuitive expectations that the elastic properties of the system with particles interacting through HCRYP at high pressures are well approximated by hard spheres, whereas in the low pressure regime they are close to those obtained for the system with pure Yukawa interactions. It also demonstrated clearly that, in the “transition region”, when the HCRYP system is neither close to the Yukawa system nor to the hard sphere system, its Poisson's ratio in the directions [110][110] exceeds the ranges obtained for potentials composing the HCRYP.

The section on Q2D auxetics contains papers related to layers, laminates, membranes, woven fabrics, and auxetic yarns.

A parametric analysis on the in‐plane impact capabilities of thermoplastic polyurethane (TPU) based butterfly, antitetrachiral, cross‐chiral and hexagonal honeycombs and the validation of the explicit FE models associated to those configurations is presented ‘Validation of a Finite Element Modeling Process for Auxetic Structures under Impact’ by Todd Shepherd et al.^[6^] The load cases there were related to flat or large spherical indentors covering the width of the lattice configurations, which are quite representative of sport engineering protective equipment. The authors performed a careful analysis of the TPU material used to manufacture the samples, as well as identifying model correlations and parameters to simulate new loading cases and geometry scenarios in a robust and repeatable manner. The paper provides a commendable and very practical and useful addition to the body of literature associated to the crashworthiness of auxetics, currently being developed worldwide.

Fossil‐based epoxy/carbon fiber composites with symmetric angle‐play stacking sequences and used as piezoelectric energy harvesters are described by Qingqing Lu et al. in ‘Edge Effects of a Hexagonal Honeycomb on the Poisson's Ratio and Young's Modulus’.^[7^] The authors consider there classical stacking sequences first proposed by Herakovitch to obtain through‐the‐thickness positive, zero and negative Poisson's ratios, and use these composites as platforms for energy harvesters with lead‐zirconate‐titanate patches. They use classical laminate theory, FE method and experiment to explore the effect provided by the through‐the‐thickness Poisson's ratio due to the composites stacking sequence on the energy harvesting efficiency of the laminates. The results show that composites with near‐zero Poisson's ratios effect are particularly suitable for energy harvesting at low frequencies, and those composites together with the auxetic ones possess the highest specific voltage densities.

Another type of auxetic core, this time for dome‐shaped sandwich panels, is proposed by Krzysztof Pelinski, Jerzy Smardzewski, and Jakub Narojczyk in their paper ‘Stiffness of Synclastic Wood‐Based Auxetic Sandwich Panels’.^[8^] The peculiarity of the core and the panels shown there does not lie only in the shape of the composite, but also on its composition (wood). The authors describe experimental panels made of paper and WoodEpox composites cores and plywood facings. One can also find in the paper analytical and FE models which consider a central indentation into shallow sandwich spheres/caps. Panels with paper core and plywood skins possess the largest stiffness indentation, although WoodEpox composites show promise to replace conventional core materials. This paper provides a first look into the analysis of dome‐shaped and shallow curved shells sandwich structures with auxetic cores and bio‐based materials, including the skins.

Two interesting papers in this section extend the ‘helical auxetics’ concept originally proposed more than a decade ago by Patrick Hook and Kenneth E. Evans of the University of Exeter.^[9^] In ‘Theoretical Modeling on the Deformation Behavior of Auxetic Tubular Braid Made from Modified Circular Braiding Technique’ Ning Jiang, Yu Chen, and Hong Hu ^[10^] provide a theoretical analysis of auxetic tubular braid formed with three types of component yarns having different diameter and modulus which is validated using experimental data. This model is said to provide an effective tool for understanding the deformation pattern of the braid. In the article ‘Manufacture and Evaluation of Auxetic Yarns and Woven Fabrics’, Yajie Gao et al. ^[11^] report their work aimed at optimizing the auxetic yarn and fabric manufacturing processes whilst establishing a better understanding of the influence of yarn and fabric parameters on auxeticity.

Adeel Zulifqar, Tao Hua, and Hong Hu in ‘Single‐ and Double‐Layered Bistretch Auxetic Woven Fabrics Made of Nonauxetic Yarns Based on Foldable Geometries’ ^[12^] report on recent development of auxetic textile fabrics. Specifically they consider woven fabrics made from nonauxetic yarns which display auxetic fabric response based on zigzag foldable motifs. The foldable fabrics are achieved in practice by employing elastic and nonelastic yarns, and creating differential contraction/shrinkage weave combinations. Single‐layered and double‐layered fabrics based on out‐of‐phase and parallel in‐phase zigzag foldable geometries, respectively, are reported. All fabrics reported display anisotropic large strain (up to 100% applied tensile strain) auxetic response. The effects of loose weave segments and elastic yarns are considered for the single‐layered fabrics and found to be useful in tailoring the auxetic response. Such fabrics are considered to lead to improved comfort and fit in clothing and apparel applications such as maternity and sportswear.

Auxetic structures also based on textile yarns are proposed in the paper ‘Numerical Analysis of Binding Yarn Float Length for 3D Auxetic Structures’ from Hassan Iftekhar et al.^[13^] The authors here investigated how the Poisson's ratio varies within the different textiles by parametrizing the binding yarn float length and the number of layers in the textile configurations. The authors perform the analysis using a FE code over ten different yarn architectures, also describing in detail the effect of the mesh size and the applied force effects on the thickness of the textiles. The results show that the proposed textiles can provide Poisson's ratios of −0.33 when the textiles are subjected to forces of 1 kN. The results add to the knowledge base of negative Poisson's ratio materials and are certainly of interest to the growing auxetic textile community.

This section is closed by a theoretical analysis presented by Teik‐Cheng Lim so as to be able to compute with sufficient accuracy the stresses in rectangular membranes having different aspect ratios, Poisson's ratios, Young's moduli and thickness.^[14^] Through this analysis in the article ‘Maximum Stresses in Rectangular Auxetic Membranes’, Lim was able to conclude that the use of auxetic materials with low Young's modulus is ideal for lowering the extent of stresses in rectangular membranes subjected to uniform loads.

In the section on 2D auxetics Sławomir Czarnecki and Tomasz Łukasiak propose in ‘Recovery of the Auxetic Microstructures Appearing in the Least Compliant Continuum Two‐Dimensional Bodies’ a very interesting approach to identify minimal compliance designs in 2D materials systems made of inhomogeneous distributions of local isotropic or square symmetry mechanical properties.^[15^] The authors identify in this way several classes of auxetic representative volume elements with different sets of periodicity and tessellations based on single or several fibres. This is a paper that provides a very robust numerical framework to design 2D cellular structures configurations having minimal compliance and auxetic characteristics.

Wang and co‐authors present two papers on auxetic cellular solids. In the first paper, ‘Enhanced Auxetic and Viscoelastic Properties of Filled Reentrant Honeycomb' by Yun‐Che Wang, Hsiang‐Wei Lai, and Xuejun James Ren,^[16^] the effects of filler material on the Young's modulus, Poisson's ratio and viscoelastic damping responses of square‐symmetric star honeycombs are investigated using Finite Element Modelling (FEM). Filler material location (inside and/or in between the star cells) and mechanical response variations are considered. It is found that the effective Poisson's ratio can be tailored through careful filler location or properties’ selection. The viscoelastic modulus and damping are most enhanced for the all‐filled system, with the inner‐filled system showing the lowest enhancements in these properties. The second paper, ‘Effective Mechanical Responses of a Class of 2D Chiral Materials’ by Yun‐Che Wang, Tsai‐Wen Ko, and Xuejun Ren,^[17^] also uses FEM in a comparative study of the mechanical properties of square‐symmetric chiral and non‐chiral honeycombs comprising circular nodes connected by four ligaments at each node. The Poisson's ratio of the system, which can be tailored by changing the angle of the connecting ligaments or their length, undergoes a transition from positive to negative values as these parameters increase beyond threshold values. Tension or compression coupling with bending is demonstrated in the chiral system.

Two‐dimensional missing rib and cross‐chiral structures under in‐plane crushing load are extensively evaluated in ‘Numerical and Experimental Studies on the Deformation of Missing‐Rib and Mixed Structures under Compression’ by Cong Tang et al.^[18^] The paper considers four different tessellations simulated using explicit FE models benchmarked by analogous 3D printed specimens made of thermoplastic elastomers. The results show a good correlation between experiments and numerical datasets. The missing rib structures feature either global in‐plane rotations or local stretching/rotations distributions that provide a more uniform compression behaviour under uniaxial loading. The configurations presented here could be useful for the mechanical metamaterials designers.

In ‘A Simple Methodology to Generate Metamaterials and Structures with Negative Poisson's Ratio’ Xiang Yu Zhang and Xin Ren ^[19^] present a detailed investigation of two‐dimensional systems which can be converted into auxetics through buckling, i.e. “generate buckling‐induced metamaterials and structures with negative Poisson's ratio”. They specifically introduce the concept of “pattern scale factor (PSF)” and employ it into several case studies. This is an interesting continuation of the compression induced auxeticity of 2D foams – compress, un‐stress, and stabilise – see Artur A. Pozniak et al.,^[20^] which was earlier applied to various 3D foams by Rod S. Lakes,^[21^] who unstressed materials by high temperature and stabilised them by decreasing it, and Ruben Gatt et al.,^[22^] who unstressed materials chemically (by using solvents) and stabilised them by drying.

Poisson's ratio for two‐dimensional (2D) materials of square symmetry, called also 2D cubic materials, was discussed in ‘Another Look at Auxeticity of Two‐Dimensional Square Media’ by Natalia Bielejewska et al.^[23^] Elastic moduli ratios, X = G/K and Y = G/W, were used to parametrise the square media, where G, W are the shear moduli and K is the bulk modulus. It was shown that the entire XY plane is partitioned into nonauxetic, partially auxetic, and auxetic regions by two straight lines. A representation of the XY plane with the elastic constants ratio λ = C₁₂/C₄₄ was exploited to investigate 2D square materials under nonzero hydrostatic pressure. It was demonstrated that 2D square materials with λ > 0 can be auxetic only under negative pressure. Auxeticity of square and cubic (three‐dimensional) materials were compared.

This section is closed by three articles by researchers from the University of Malta who employ various modelling and simulation techniques to study and optimise systems which exhibit negative mechanical behaviour. In the article ‘Tuning the Mechanical Properties of the Anti‐Tetrachiral System Using Nonuniform Ligament Thickness’ Farrugia et al. make use of analytical modelling and FE analysis so as to simulate and predict the behaviour of modified forms of the anti‐tetrachiral system where the ligaments have non‐uniform thickness or stiffness. The authors show that such a variation has a significant effect on the stiffness of the system but less effect on the Poisson's ratio.^[24^] The next article, by Pierre‐Sandro Farrugia et al., entitled ‘Edge Effects of a Hexagonal Honeycomb on Poisson's Ratio and Young's Modulus’ shows the extensive difference between the behaviour of periodically tessellated systems and their finite‐sized equivalents where edge effects could become so pronounced that the Poisson's ratio could actually change its sign.^[25^] In the last article of this section, ‘Smart Honeycomb “Mechanical Metamaterials” with Tunable Poisson's Ratios’, James N. Grima‐Cornish et al. show how the composite honeycombs having T‐shaped junctions could be made to exhibit temperature‐dependent Poisson's ratios.^[26^]

This time the section other systems with “negative” characteristics is represented by three papers. The first of them, ‘On the Design of Multimaterial Honeycombs and Structures with T‐Shaped Joints Having Tunable Thermal and Compressibility Properties’ by Reuben Cauchi et al., shows that the composite honeycombs having T‐shaped junctions, which were also the subject of the last paper of the previous section, can exhibit negative thermal expansion and/or negative compressibility, the magnitude of which could be fine‐tuned though design.^[27^]

The second article of this section, ‘Negative Hygrothermal Expansion of Reinforced Double Arrowhead Microstructure’, discusses another very interesting anomalous phenomenon, which is being referred to as “negative hygroscopic expansion”, the condition where a substance is shrinking rather than expanding when subjected to immersion in a fluid. In this work Teik‐Cheng Lim ^[28^] studies a ‘double arrowhead’ microstructure and studies its and “negative thermal expansion” characteristics. This permits elucidation of the conditions resulting in “negative hygrothermal expansion” as well as the condition of “zero hygrothermal expansion”.

The last paper in this volume is ‘Statistical Analysis and Molecular Dynamics Simulations of the Thermal Conductivity of Lennard–Jones Solids Including Their Pressure and Temperature Dependencies’ by D.M. Heyes, D. Dini, and E. R. Smith. They used equilibrium molecular dynamics simulations to study the thermal conductivity of a Lennard–Jones solid and the sublimation line. Their analysis revealed that for short periods of time the thermal conductivity can be negative. This unusual feature was evident along the sublimation line isobar and a low‐temperature isotherm going to high densities. For more details on this fascinating result, readers are invited to consult the original article.^[29^]

具有负泊松比的材料和模型（称为“动力学”）以及具有“负”特性的其他系统的当前体积是该问题上第十四个物理状态实体问题。^[ 1 ^]该卷包含24篇论文。其中21个关于辅助材料和模型，分为三部分：三维（3D）辅助，准二维（Q2D）辅助和二维（2D）辅助。其余论文涉及具有“负”特性的其他系统。

3D动力学的部分从挤压扭扭耦合效应开始，李建恒，Chan Soo Ha和Roderic S. Lakes在手性3D各向同性晶格中观察到了这种效应。他们的论文“观察手性3D各向同性晶格中的挤压-扭曲耦合” ^[ 2 ^]显示了一些非常有趣的晶格实验样品结果，这些结果也以以前的有限元（FE）结果为基准。作者运用Cosserat理论，不仅验证了使用视频量测引伸法和数字图像相关技术测得的接近零的泊松比，而且还证明了泊松比的大小依赖性，对于足够数量的像元，泊松比预期为负值。 。

Nejc Novak等人在“手性辅助复合材料夹芯板对模拟弹丸撞击的碎片的响应”一文中发表了论文。，^[ 3 ^]三维手性晶格被用作夹芯板中承受弹道冲击的核心。芯是通过选择性的电子束熔化从合金粉末中制成的，并与铝合金板连接在一起。通过压缩和拉伸，在准静态和大应变速率下测试了流变型芯和平板。显式有限元仿真与实验结果之间观察到非常好的相关性。然后分别对夹心板和夹板进行弹道冲击（数值和实验）。核心的存在显着降低了弹丸穿过面板的速度。模拟还表明，膨胀芯的孔隙率变化不会影响面板的整体变形响应。

在Prateek Verma，Chaobin He和Anselm C. Griffin撰写的一篇非常有趣的文章“液晶聚合物中的助燃响应的影响：X射线散射和空间填充分子建模”中，^[ 4 ^]作者给出了非常详细和关键的信息讨论由Anselm Griffin教授领导的数十年来在有关高能液晶聚合物的研究中取得的显著成果，该学者的名字与高能化学之间的联系非常紧密。重要的是，作者提供了一些重要的见解，说明如何最好地进行这项工作。

该部分的最后一篇文章是Konstantin V.Tretiakov和Krzysztof W.Wojciechowski撰写的``软汤河势和硬核相互作用对硬核斥力汤河颗粒的面心立方晶体的消融性的影响'' 。^[ 5 ^]这些作者研究了三个粒子系统的面心立方相的弹性特性和泊松比，这三个粒子系统分别与硬球势，斥力汤川势和由以下组成的硬核斥力汤川势（HCRYP）相互作用前两种潜力。在所有系统的熔化和密堆积之间的较大压力范围内，比较了等压-等温集成中的蒙特卡罗模拟结果。他们每个人都观察到部分促生长作用，并揭示了在HCRYP中结合的硬电势和软电势的作用。这项研究证实了直观的期望，即在高压下具有通过HCRYP相互作用的颗粒的系统的弹性特性可以很好地近似为硬球体，而在低压状态下，它们接近于具有纯Yukawa相互作用的系统所获得的压力。它还清楚地表明，在“过渡区”，当HCRYP系统既不接近汤川系统也不接近硬球系统时，其泊松比在[110] [110]方向上超过了构成HCRYP的电位所获得的范围。

Q2D auxetics一节包含与层，层压板，膜，机织织物和auxetic纱线有关的论文。

对基于热塑性聚氨酯（TPU）的蝶形，反四手性，交叉手性和六角形蜂窝的平面内冲击能力进行了参数分析，并验证了与这些构型相关的显式有限元模型的有效性。Todd Shepherd等人在“冲击下的助推结构” 。^[ 6 ^]那里的载荷情况与覆盖晶格结构宽度的扁平或大型球形压头有关，这些压头完全代表了运动工程防护设备。作者对用于制造样品的TPU材料进行了仔细的分析，并确定了模型的相关性和参数，从而以可靠且可重复的方式模拟了新的加载工况和几何形状情况。该论文为目前在世界范围内发展的与止呕性相关的文献提供了值得称赞的，非常实用和有用的补充。

Qingqing Lu等人描述了化石基环氧/碳纤维复合材料，该复合材料具有对称的角度游隙堆叠顺序，并用作压电能量收集器。在“六角蜂窝对泊松比和杨氏模量的边缘影响”中。^[ 7 ^]作者认为，Herakovitch首先提出了经典的叠加序列，以获取整个厚度的正，零和负泊松比，并将这些复合材料用作具有锆钛酸铅斑的能量收集器的平台。他们使用经典的层压板理论，有限元方法和实验来研究由于复合材料堆叠顺序而导致的整个厚度的泊松比对层压板能量收集效率的影响。结果表明，具有接近零泊松比效应的复合材料特别适用于低频能量收集，并且那些具有膨胀性的复合材料具有最高的比电压密度。

Krzysztof Pelinski，Jerzy Smardzewski和Jakub Narojczyk在他们的论文“同步塑性木基辅助夹芯板的刚度”中提出了另一种类型的发胀芯，这一次是圆顶形夹芯板。^[ 8 ^]芯和此处显示的面板的特殊性不仅在于复合材料的形状，还在于其成分（木材）。作者介绍了由纸和WoodEpox复合材料芯和胶合板饰面制成的实验面板。人们还可以在论文中找到分析和有限元模型，其中考虑到浅夹层球体/盖子的中心凹痕。具有纸芯和胶合板表皮的面板具有最大的硬度压痕，尽管WoodEpox复合材料显示出有望取代传统的芯材。本文首先分析了带有膨胀核心和生物基材料（包括皮肤）的圆顶形和浅弯曲壳夹心结构。

本节中的两篇有趣的论文扩展了埃克塞特大学的帕特里克·胡克（Patrick Hook）和肯尼斯·埃文斯（Kenneth E.Evans）最初提出的“螺旋线膨胀”概念。^[ 9 ^]在“采用改进的圆形编织技术制成的辅助管状编织物变形行为的理论模型”中，姜宁，于晨，胡洪 ^[ 10 ^]提供了由具有不同直径和模量的三种类型的成分纱线形成的膨胀管状编织物的理论分析，该分析已通过实验数据进行了验证。据说该模型为理解编织物的变形模式提供了有效的工具。高 亚杰等在“助剂纱线和机织织物的生产和评估”一文中。^[ 11 ^]报告了他们的工作，旨在优化发条纱线和织物的制造工艺，同时建立了对发条的影响的纱线和织物参数的更好的理解。

Adeel Zulifqar，Tao Hua和Hong Hu在“基于可折叠几何形状的非膨松纱制成的单层和双层Bistretch机织机织面料”中^[ 12 ^]关于增塑纺织品的最新发展的报告。具体而言，他们考虑了由非增生纱线制成的机织织物，这些织物基于之字形可折叠图案显示出增生织物的响应。在实践中，可折叠织物是通过使用弹性和非弹性纱线，并产生不同的收缩/收缩编织组合而实现的。据报道，分别基于异相和平行同相之字形可折叠几何形状的单层和双层织物。报告的所有织物均显示各向异性大应变（施加的拉伸应变高达100％）的拉力响应。对于单层织物，考虑了松散的编织段和弹性纱的影响，并发现它们在调整拉幅响应方面很有用。

Hassan Iftekhar等人在论文“ 3D辅助结构的结合纱浮漂长度的数值分析”中提出了也基于纺织纱线的辅助结构。^[ 13 ^]作者在本文中通过参数化绑结纱的浮线长度和纺织品结构中的层数来研究泊松比在不同纺织品中如何变化。作者使用FE代码对十种不同的纱线结构进行了分析，还详细描述了网眼尺寸的影响以及施加的力对纺织品厚度的影响。结果表明，当纺织品受到1 kN的力时，所提出的纺织品可以提供-0.33的泊松比。结果增加了负泊松比材料的知识库，并且对于不断增长的贫民窟纺织界无疑是令人感兴趣的。

本节以Teik-Cheng Lim提出的理论分析结束，以便能够足够准确地计算具有不同长宽比，泊松比，杨氏模量和厚度的矩形膜中的应力。^[ 14 ^]通过文章“矩形辅助薄膜中的最大应力”的分析，Lim可以得出结论，使用低杨氏模量的膨胀材料对于降低承受均布载荷的矩形膜的应力范围是理想的。

在关于2D动力学 的章节中，SławomirCzarnecki和TomaszŁukasiak在“恢复最小顺次连续体中出现的微结构的恢复”中提出了一种非常有趣的方法，用于识别由局部各向同性分布不均匀的2D材料系统中的最小顺应性设计。或方形对称的机械性能。^[ 15 ^]作者以此方式识别出几类基于单个或几根纤维的具有不同周期性和方差的胀缩代表性体积元素。这篇论文提供了非常强大的数值框架来设计具有最小柔度和膨胀特性的2D蜂窝结构配置。

Wang和他的合著者发表了两篇关于膨胀细胞固体的论文。在第一篇文章，“增强填充折返蜂窝的拉胀和粘弹性特性”由运车王乡，潍莱，和学军詹姆斯仁，^[ 16 ^]利用有限元模型（FEM）研究了填料对杨氏模量，泊松比和方形对称星形蜂窝体粘弹性阻尼响应的影响。考虑填充材料的位置（星形电池内部和/或之间）和机械响应变化。发现有效的泊松比可以通过仔细的填料位置或性质的选择来调整。对于全填充系统，粘弹性模量和阻尼得到最大增强，而内填充系统则表现出这些特性的最低增强。第二篇论文，“一类2D手性材料的有效力学响应”，作者：王运志，高才文和任学军，^[ 17 ^]还使用有限元法对方形对称的手性和非手性蜂窝的力学性能进行了比较研究，该蜂窝由圆形结点组成，每个结点由四个韧带连接。可以通过改变连接韧带的角度或长度来定制系统的泊松比，当这些参数增加到阈值以上时，泊松比会从正值变为负值。在手性体系中证明了具有弯曲的拉伸或压缩耦合。

Cong Tang等人在“压缩状态下的缺失肋骨和混合结构变形的数值和实验研究”中广泛评估了平面内破碎载荷下的二维缺失肋骨和交叉手性结构。^[ 18 ^]本文考虑了使用显式有限元模型模拟的四个不同的镶嵌，这些有限元模型以热塑性弹性体制成的类似3D打印样本为基准。结果表明，实验与数值数据集之间具有良好的相关性。缺少的肋骨结构具有全局面内旋转或局部拉伸/旋转分布，从而在单轴载荷下提供了更均匀的压缩行为。此处介绍的配置对于机械超材料的设计人员可能有用。

在“一种简单的以负泊松比生成超材料和结构的方法论”中，张向宇和任仁 ^[ 19 ^]提出了对二维系统的详细研究，该系统可以通过屈曲转化为膨胀，即“产生屈曲诱发的超材料和结构”。泊松比为负的结构”。他们专门介绍了“模式比例因子（PSF）”的概念，并将其应用于几个案例研究中。这是2D泡沫由压缩引起的膨胀性的有趣延续-压缩，无应力和稳定-参见Artur A. Pozniak等。，^[ 20 ^]先前由Rod S. Lakes应用于各种3D泡沫，^[ 21 ^]谁通过高温使材料不受应力，并通过降低其来稳定它们，Ruben Gatt等人。，^[ 22 ^]用化学方法使材料不受应力（通过使用溶剂）并通过干燥使其稳定。

Natalia Bielejewska等人在“另一种观察二维方介质的流变性”中讨论了方形对称的二维（2D）材料（也称为2D立方材料）的泊松比。^[ 23 ^]弹性模量比X = G / K和Y = G / W用来对方形介质进行参数化，其中G，W是剪切模量，K是体积模量。结果表明，整个XY平面通过两条直线划分为非膨胀区，部分膨胀区和膨胀区。利用弹性常数比λ  =  C ₁₂ / C ₄₄的XY平面表示法研究了在非零静水压力下的二维正方形材料。证明了λ  > 0的2D正方形材​​料仅在负压下会膨胀。比较了正方形和立方（三维）材料的膨胀性。

本节由马耳他大学的研究人员撰写的三篇文章结尾，他们使用各种建模和仿真技术来研究和优化表现出负面机械行为的系统。在Farrugia等人的文章“使用不均匀的韧带厚度调节抗四手性系统的机械性能”中。利用分析模型和有限元分析来模拟和预测韧带厚度或刚度不均匀的抗四手性系统修饰形式的行为。作者表明，这种变化对系统的刚度有重大影响，但对泊松比的影响较小。^[ 24 ^]下一篇文章，由Pierre-Sandro Farrugia等撰写。题为``六角蜂窝对泊松比和杨氏模量的边缘效应''显示了周期性细分的系统的行为与其有限尺寸的等效物之间的广泛差异，在这种情况下，边缘效应可能变得如此明显，以至于泊松比实际上可以改变其符号。^[ 25 ^]在本节的最后一篇文章中，James N. Grima-Cornish等人发表了“具有可调泊松比的智能蜂窝“机械超材料” 。展示了如何使具有T形结的复合蜂窝具有与温度相关的泊松比。^[ 26 ^]

这次，具有“负”特性的其他系统部分由三篇论文代表。其中第一个是Reuben Cauchi等人的“关于具有可调节的热和压缩特性的T形接头的多材料蜂窝和结构的设计” ，表明具有T形结的复合蜂窝也是该主题。上一节的最后一篇论文可能会显示出负的热膨胀和/或负的可压缩性，其大小可以通过设计进行微调。^[ 27 ^]

本节的第二篇文章“增强双箭头微结构的负湿热膨胀”讨论了另一个非常有趣的异常现象，被称为“负吸湿膨胀”，即物质在受到压缩时会收缩而不是膨胀的情况。浸入液体中。在这项工作中，Teik-Cheng Lim ^[ 28 ^]研究了“双箭头”的微观结构，并研究了其“负热膨胀”特性。这允许阐明导致“负湿热膨胀”的条件以及“零湿热膨胀”的条件。

该卷的最后一篇论文是DM Heyes，D.Dini和ER Smith撰写的“ Lennard-Jones固体的导热系数的统计分析和分子动力学模拟，包括其压力和温度依赖性” 。他们使用平衡分子动力学模拟研究了Lennard-Jones固体和升华线的热导率。他们的分析表明，在短时间内导热系数可能为负。沿升华线等压线和低温等温线趋于高密度时，这一异常特征显而易见。有关此引人入胜的结果的更多详细信息，请读者查阅原始文章。^[ 29 ^]