Negative Poisson's Ratio Research Articles

Promising mechanical, electronic and piezoelectric properties of grapheneplus-like BCN monolayer: insights from first-principles.

Two-dimensional (2D) carbon allotropes, together with their binary and ternary counterparts, have attracted substantial research interest due to their peculiar geometries and properties. Among them, grapheneplus, a derivative of penta-graphene, has been proposed to exhibit unusual mechanical and electronic behaviour. In this work, we perform a comprehensive first-principles study on its isoelectronic and isostructural analogue, a grapheneplus-like BCN (gp-BCN) monolayer. It is found that this gp-BCN system exhibits robust structural stability from energetic, dynamic, thermal, and mechanical perspectives. A remarkable anisotropy is observed in its mechanical behaviour, which even presents in-plane auxeticity with a high negative Poisson's ratio of -0.3. Different from the semimetallic grapheneplus one, the gp-BCN monolayer is a semiconductor with a direct band gap of 3.23 eV. High electron mobilities up to 103 cm2 V-1 s-1 appear in the gp-BCN system, which are one to two orders of magnitude greater than the hole mobilities. Furthermore, due to the breaking of inversion symmetry, the gp-BCN monolayer exhibits spontaneous out-of-plane polarization, yielding prominent out-of-plane piezoelectric responses that are comparable to those of Janus MoSSe, WSSe and H-decorated BN systems. Our study demonstrates that the BCN analogue of grapheneplus possesses promising mechanical, electronic, and piezoelectric properties, rendering it promising for applications in nanoelectronics and mechanical nanosensors.

A Review on Porous Structure Negative Poisson's Ratio Metamaterials

Metamaterials with a porous structure possess a number of advantageous properties, including low mass, high specific strength, and a high energy absorption rate. When subjected to impact or compression, these materials exhibit excellent mechanical properties, which has led to their use in a variety of aerospace applications in recent years. In comparison with traditional porous materials, metamaterials possess mechanical and physical properties that traditional materials lack. This distinguishes them from traditional materials and provides new ideas for solving engineering problems. Starting from this deformation mechanism of concave contraction of such structures, this paper details the modeling of several types of porous negative Poisson's ratio superstructures, such as honeycomb, foam and tubular structures, and focuses on the mechanical properties of porous structures in terms of elasticity, impact resistance, and energy absorption when subjected to external forces. The paper commences with an exposition of the mechanism of negative Poisson's ratio effect of porous structure, accompanied by a discourse on the extant research status of several prevalent types of porous negative Poisson's ratio superstructures. Thereafter, the deformation mechanism of porous negative Poisson's ratio metamaterials under compressive load and impact is examined. conditions is introduced, and finally, the practical application of porous negative Poisson's ratio metamaterials in the fields of automobile industry, shipbuilding and other engineering fields are summarized, and the future of porous negative Poisson's ratio metamaterials is reviewed based on the existing research results. Finally, the practical applications of negative Poisson's ratio metamaterials with porous structure in engineering fields such as automobile industry and shipbuilding are summarized, and the future development trend and application prospects are prospected based on the existing research results.

Design and Energy Absorption Study of an Asymmetric Windmill‐Style Negative Poisson's Ratio Honeycomb Structures

The negative Poisson's ratio (NPR) structure, as one of the representatives of advanced lightweight honeycomb materials, has good application prospects in aerospace, vehicles, biomedical, and other fields due to its unique deformation mechanism and huge energy absorption potential. In this article, a 2D asymmetric windmill‐style composite honeycomb (AWH) with NPR effects is presented and its compression properties are systematically assessed using both axial compression experiments and simulations. Through the experimental results, the accuracy and applicability of the finite‐element model are verified, indicating that the shape of the rotating arrangement and the stable internal design of the triangle make it have significantly higher energy absorption capacity than traditional symmetric reentrant honeycomb structures. In addition, the influence of the height, width, and cell spacing of asymmetric unit cell indentation points on the compression characteristics of AWH under axial quasi‐static compression conditions is further analyzed through orthogonal simulation experiments. In this study, a certain theoretical basis for the design and energy absorption application of NPR materials is provided, indicating that AWH has excellent mechanical properties and broad application prospects.

Comparative experimental investigation of direct tension and Brazilian splitting behaviors of thermally-damaged crystalline rocks: unique negative poisson's ratio effect

Comparative experimental investigation of direct tension and Brazilian splitting behaviors of thermally-damaged crystalline rocks: unique negative poisson's ratio effect

Optimising β-Ti21S Alloy Lattice Structures for Enhanced Femoral Implants: A Study on Mechanical and Biological Performance.

The metastable β-Ti21S alloy exhibits a lower elastic modulus than Ti-6Al-4V ELI while maintaining high mechanical strength and ductility. To address stress shielding, this study explores the integration of lattice structures within prosthetics, which is made possible through additive manufacturing. Continuous adhesion between the implant and bone is essential; therefore, auxetic bow-tie structures with a negative Poisson's ratio are proposed for regions under tensile stress, while Triply Periodic Minimal Surface (TPMS) structures with a positive Poisson's ratio are recommended for areas under compressive stress. This research examines the manufacturability and quasi-static mechanical behaviour of two auxetic bow-tie (AUX 2.5 and AUX 3.5) and two TPMS structures (TPMS 2.5 and TPMS 1.5) in β-Ti21S alloy produced via laser powder bed fusion. Micro-CT reveals printability issues in TPMS 1.5, affecting pore size and reducing fatigue resistance compared to TPMS 2.5. AUX 3.5's low stiffness matches cancellous bone but shows insufficient yield strength and fatigue resistance for femoral implants. Biological tests confirm non-toxicity and enhanced cell activity in β-Ti21S structures. The study concludes that the β-Ti21S alloy, especially with TPMS 2.5 structures, demonstrates promising mechanical and biological properties for femoral implants. However, challenges like poor printability in TPMS 1.5 are acknowledged and should be addressed in future research.

Structurally Transformable and Reconfigurable Hydrogel-Based Mechanical Metamaterials and Their Application in Biomedical Stents.

Mechanical metamaterials exhibit several unusual mechanical properties, such as a negative Poisson's ratio, which impart additional capabilities to materials. Recently, hydrogels have emerged as exceptional candidates for fabricating mechanical metamaterials that offer enhanced functionality and expanded applications due to their unique responsive characteristics. However, the adaptability of these metamaterials remains constrained and underutilized, as they lack integration of the hydrogels' soft and responsive characteristics with the metamaterial design. Here, we propose structurally transformable and reconfigurable hydrogel-based mechanical metamaterials through three-dimensional (3D) printing of lattice structures composed of multishape-memory poly(acrylic acid)-chitosan hydrogels. By incorporating reversible shape-memory mechanisms that control the structural arrangements of the lattice, these metamaterials can exhibit transformable and reconfigurable mechanical characteristics under various environmental conditions, including auxetic behavior, with Poisson's ratios switchable from negative to zero or positive. These adaptable mechanical responses across different states arise from structural changes in lattice, surpassing the gradual changes observed in conventional stimuli-responsive materials. The application of these metamaterials in multimode biomedical stents demonstrates their adaptability in practical settings, allowing them to transition between expandable, nonexpandable, and shrinkable states, with corresponding Poisson's ratios. By integrating multishape-memory soft materials with metamaterial design, we can significantly enhance their functionality, advancing the development of smart biomaterials.

αnhm-GeSe: a multifunctional semiconductor combining auxeticity and piezoelectricity.

Multifunctional materials with outstanding performance have enormous potential applications in the next generation of nanodevices. Using first principles calculations, we design a series of multifunctional two-dimensional materials in monolayer αnhm-GeSe (n, m = 1, 2) that combine auxeticity and piezoelectricity. Due to the similar local structures of α-GeSe and h-GeSe, monolayer αnhm-GeSe can be designed through the combination of these two materials. Elastic constants and phonon dispersion curves confirm that all the structures are mechanically and dynamically stable. Monolayer αnhm-GeSe exhibits auxetic properties with an in-plane negative Poisson's ratio along the diagonal direction. An out-of-plane negative Poisson's ratio effect can be observed by applying tensile strain in the x-direction, which is beneficial for mechanical devices. Only a few materials are both in-plane and out-of-plane auxetic. In addition, monolayer αnhm-GeSe can exhibit electric polarization because of the breaking of the central symmetry, demonstrating in-plane piezoelectric properties with strong anisotropy. The above results make monolayer αnhm-GeSe an interesting multifunctional material and provide a candidate material for a nanoscale device.

Two-dimensional multifunctional metal-organic frameworks with large in-plane negative Poisson ratios and photocatalytic water splitting properties.

Auxetic materials with multifunctional properties are highly sought after for application in modern nano-devices. However, the majority of reported inorganic auxetic materials exhibit low negative Poisson's ratios (NPR), poor flexibility, and limited functionality. In this study, we employ density-functional-theory (DFT) first-principles simulations to design a series of two-dimensional (2D) metal-organic frameworks (MOFs) M2C4X4 (M = Cu, Ag, Au; X = O, S, NCN) that display intriguing auxetic behavior, superior flexibility and appropriate photocatalytic water-splitting properties. These M2C4X4 MOFs are assembled from carbon tetragon motifs and exist in both cis- and trans-isomer forms, with the NPR ranging from -0.17 to -0.90. Notably, trans-Cu2C4(NCN)4 exhibits a high NPR of -0.90, while cis-Cu2C4(NCN)4 achieves an NPR of -0.67. Both isomers demonstrate excellent flexibility, characterized by ultra-low Young's modulus and high fracture strengths. Furthermore, their direct band gaps, strong light-harvesting capabilities, and long excited-state lifetimes make them promising candidates for the photocatalytic oxygen evolution reaction in water. These results provide a viable strategy for the design and synthesis of novel optoelectronic multifunctional materials.

Dynamic response analysis of three-dimensional U-shaped negative Poisson's ratio periodic structures

Dynamic response analysis of three-dimensional U-shaped negative Poisson's ratio periodic structures

Buckling and post-buckling behavior of auxetic cellular structures

In this work, experimental tests and numerical simulations are carried out to investigate the buckling behavior and failure modes of auxetic cellular structures and sandwich panels with auxetic cores. Different Poisson's ratios and densities are considered to evaluate the impact of these parameters on the deformation mechanisms under uniaxial compression loading. The numerical analysis is performed using the Riks method, while considering geometric nonlinearity and elastoplastic behavior. The results indicate that negative Poisson's ratio and structure density have a significant influence on the buckling critical stress and the failure mechanisms of cellular structures. Although the inverted honeycomb and the double arrowhead with different Poisson's ratios exhibit similar load capacity, facesheet failure is more pronounced with the conventional inverted honeycomb. This result can be attributed to the dominant effect of the facesheet on the load evolution. The effects of the cell-wall thickness and the facesheet thickness on the buckling load are also discussed based on the finite element model.

A New Polymeric Hybrid Auxetic Structure Additively Manufactured by Fused Filament Fabrication 3D Printing: Machine Learning-Based Energy Absorption Prediction and Optimization.

The significance of this paper is an investigation into the design, development, and optimization of a new polymeric hybrid auxetic structure by additive manufacturing (AM). This work will introduce an innovative class of polymeric hybrid auxetic structure by the integration of an arrow-head unit cell into a missing rib unit cell, which will be fabricated using fused filament fabrication (FFF) technique, that is, one subset of AM. The auxetic performance of the structure is validated through the measurement of its negative Poisson's ratio, confirming its potential for enhanced energy absorption. A chain of regression, linear, and quadratic polynomial machine learning algorithms are used to predict and optimize the energy absorption capability at variant processing conditions. Amongst them, the polynomial regression model stands out with an R-squared value of 92.46%, reflecting an excellent predictive capability for energy absorption of additively manufactured polymeric hybrid auxetic structure. The optimization technique revealed that the printing speed of 80 mm/s and layer height of 200 µm were the critical values to achieve a maximum amount of energy absorption at 5.954 kJ/m2, achieved at a printing temperature of 244.65 °C. Such results also contribute to the development of AM, since they show not only the potential for energy absorption of polymeric hybrid auxetic structures but also how effective machine learning is in the optimization of the AM process.

Transitory metamaterials based on symmetrical splitting of rotating squares

Abstract Materials exhibiting a negative Poisson's ratio, known as auxetic materials, have garnered significant interest due to their unique mechanical properties and potential applications. This paper introduces a new class of auxetic metamaterials based on modified interconnected rotating rigid squares, where each square can bifurcate into two or quadfurcate into four isosceles right triangles. The study explores three models categorized by their order of bifurcation or quadfurcation, ranging from purely rotating squares (zeroth order) to systems with sub-units exhibiting relative motion (first and second orders). Detailed analyses of the in-plane Poisson's ratio for these models are conducted, focusing on both infinitesimal and finite deformations. The results reveal that the proposed metamaterials demonstrate a transition in Poisson's ratio behavior, characterized either by discontinuity or continuous but non-differentiable Poisson’s ratio at the transitory state between deformation mechanisms. This transition highlights the potential of these metamaterials to exhibit tunable mechanical responses, offering insights into designing materials with customized properties for advanced engineering applications.

Biomimetic Honeycomb-like Ti3C2Tx MXene/Bacterial Cellulose Aerogel-Based Flexible Pressure Sensor for the Human-Computer Interface.

The pursuit of efficient and accurate human-computer interface design urgently requires high-performance sensors with pressure sensitivity, a wide detection range, and excellent cycling stability. Herein, a biomimetic honeycomb-like Ti3C2Tx MXene/bacterial cellulose (BC) aerogel with a negative Poisson's ratio (ν = -0.14) synthesized from the bidirectional freeze-drying method is used as the active material for a flexible pressure sensor, which exhibits high sensitivity (20.14 kPa-1), fast response time (100 ms), excellent mechanical durability (5000 cycles), and a low detection limit (responding to a grain of rice weighing about 0.022 g). Moreover, when assembled into the sandwich-structured bending sensor with the aerogel layer at just 0.8 mm in thickness, the aerogel-based device has a wide angular detection range (2.7-156.3°), high sensitivity (0.47 deg-1), and good robustness, proving outstanding electromechanical performance. Significantly, a smart glove consisting of five bending sensors fixed to the proximal knuckles and a flexible circuit board as the signal processing unit was designed for the identification of the shape, demonstrating its promising applications in the field of human-computer interaction.

Piezoelectret metamaterials with a double-V structure exhibiting tunable piezoelectric effect in a broad range

Piezoelectret metamaterials are a kind of piezoelectrets with distinctive properties such as negative Poisson's ratio and positive piezoelectric d31 coefficient. These materials hold significant promise for applications in sensing and mechanical energy harvesting. In this article, flexible piezoelectret metamaterials with a simple double-V cell structure are designed, and their properties are theoretically analyzed, simulated, and experimentally tested. The results indicate that the effective piezoelectric d33 and d31 coefficients can be tuned over a wide range by adjusting the geometric parameters of the cell. The experimental results are consistent with the theoretical prediction and simulation calculation. Differing from the piezoelectric d33 coefficient, which always has positive polarity, the sign of the piezoelectric d31 coefficient depends on Poisson's ratio of the material. In particular, d31 coefficients are negative for the materials with positive Poisson's ratio, while they have a positive sign when Poisson's ratio is negative. For a piezoelectret metamaterial sample prepared in this study, a large effective piezoelectric d31 coefficient up to 1200 pC/N is achieved experimentally. The significant piezoelectric effects in the piezoelectret metamaterials as well as their excellent mechanical adaptivity to irregular surface structures, such as the curved surfaces of humanoid robots and aircraft wings, introduce a novel solution for diverse applications.

Optimizing 3D-Printed Auxetic Structures for Tensile Performance: Taguchi Method Application on Cell Size and Shape Orientation

Auxetic structures are characterized by their unique mechanical property of exhibiting a negative Poisson's ratio, which means they expand laterally when stretched and contract laterally when compressed, contrary to conventional materials. This distinctive behavior enables auxetic materials to possess enhanced mechanical properties such as improved energy absorption, shear resistance, and indentation resistance. This study is of special novelty as it is one of the few investigations examining the effect and optimization of shape orientation and cell size on tensile mechanical properties. For this reason, a total of nine different specimens were produced using three different cell sizes (3 mm, 2 mm, 1.5 mm) and three different shape orientations (0º, 45º, 90º) using a masked stereolithography (MSLA) printer, and their tension mechanical properties were investigated. The best cell size and shape orientation were determined by Taguchi's maximum signal-to-noise ratio (S/N) analysis, and the data was analyzed with the Analysis of Variance (ANOVA) test. Specifically, a cell size of 1.5 mm and a shape orientation of 90º delivered the best performance, with a maximum fracture force of 348.44 N and energy absorption of 224.91 J. This research contributes to optimizing 3D printing for improved mechanical performance and to the field of additive manufacturing.

Vibro-acoustic behavior of partially submerged composite sandwich plates with negative Poisson’s ratio grids

Composite sandwich structures demonstrate significant potential for applications in Marine structures due to their corrosion resistance, high specific strength, and lightweight characteristics. This paper explores the underwater vibro-acoustic characteristics of composite sandwich plates featuring negative Poisson’s ratio grids. The composite sandwich plate comprises orthotropic carbon fiber and glass fiber laminates, along with a periodic grating structure. The fundamental units of the grating structure are star grids, chiral grids, and concave hexagonal grids, respectively. The vibration and noise reduction performance of the negative Poisson ratio composite sandwich plate is affirmed through comparison with the traditional regular hexagonal composite sandwich plate. The chiral and concave hexagonal grids demonstrate outstanding noise reduction capabilities, achieving up to 25 dB, though their vibration damping performance is poor. In contrast, the star grid still exhibits high acoustic response peaks but maintains a relatively stable vibration damping performance of around 5 dB. Finally, the paper explores the effects of different parameters on the vibro-acoustic behavior of composite sandwich plates with negative Poisson ratio grids, including cell equivalent Poisson ratio, panel layup angle, and plate curvature.

Energy Absorption in a Rotating Rigid Honeycomb Based on Reinforced Ribbed Plates

This article proposes a rotationally reinforced ribbed honeycomb structure by incorporating struts into the rotationally rigid honeycomb to enhance its stiffness. Finite element models of the honeycomb are developed using Abaqus/Explicit and validated through quasistatic experiments for accuracy. Based on the models, a series of studies on the honeycomb's structural behavior are conducted. Initially, the mechanical properties of the honeycomb under varying loading conditions and rib angles are analyzed. The results indicate that the RSH‐45 configuration exhibits the most favorable mechanical properties under both X‐direction and Y‐direction loading conditions. Specifically, under impact in the X‐direction, the RSH‐45 and RSH‐60 configurations demonstrate increases in energy absorption of 114.64% and 96.9%, respectively, compared to the RSH‐90 configuration. Subsequently, the mechanical properties of the RSH at different impact velocities are examined. The negative Poisson's effect of the RSH is most pronounced at low‐velocity, with the deformation modes changing as velocity increases. Under medium‐velocity impacts, RSH‐45 and RSH‐60 configurations exhibit a significant negative Poisson's ratio effect, while RSH‐75 and RSH‐90 configurations display a positive effect. In summary, reinforcing ribs produces a significant negative Poisson's ratio effect only at specific angles.

Shape Optimization of Tunable Poisson's Ratio Metamaterials With Disk B‐Splines

ABSTRACTWe propose an explicit representation method using disk B‐splines for Poisson's ratio metamaterial design. Disk B‐spline representation generalizes the concept of the B‐spline control point into a control disk, enhancing the ability to manipulate both the shape and thickness of the region. Therefore, this representation is frequently employed for shape optimization. The optimized metamaterials described by disk B‐spline are decomposed into a sequence of circles constructing one implicit function. A novel optimization model based on disk B‐spline representation is proposed, and the homogenization theory is used for calculating effective Poisson's ratio (PR). The numerical examples contained missing rib metamaterials, petal‐like metamaterials, and extreme PR metamaterials, which are studies to illustrate the advantages and effectiveness. By explicitly manipulating the parameters of the disk's B‐spline, a broad spectrum of unexpectedly negative Poisson's ratio from ‐0.1 to ‐0.9 sequences can be achieved, and arbitrary Poisson's ratios structures can be obtained through interpolating continuous parameters. It's also extended to encompass 3D structures. We validate the accuracy of our results by comparing them with simulations performed using commercial software.

Fully foldable mechanical metamaterials with isotropic auxeticity and its generated multi-mode folding form

Abstract Auxetic materials, a type of mechanical metamaterial with negative Poisson's ratios, are potentially utilized in the realms of energy absorption and engineering structures. However, most of the existing auxetic materials either contain a large amount of rotational motion or still have gaps when fully folded, which is not conducive to lifting loads. Besides, their application is limited to flexible environments due to their single-folding mode. To overcome such limitations, a fully foldable mechanical metamaterial with isotropic auxeticity is proposed by utilizing the Sarrus mechanism, and its generated multi-mode folding form is obtained in this paper. Then, the DOF, bistability and kinematic characterizations are analyzed to show the performance of the proposed structures. Finally, the parameters of the proposed fully foldable mechanical metamaterials are discussed to simplify the structures. Some prototypes are fabricated to validate the effectiveness and performance of the proposed mechanical metamaterials. The proposed mechanical metamaterials have some merits, such as isotropic auxeticity, being fully folded to achieve dense compression, being bistable with load-bearing capacity, multi-mode folding form, and one-DOF, and they have versatile potential applications in complex environments requiring high-impact resistance and flexible adaptation.

Sign-Switchable Poisson's Ratio Design for Bimodal Strain-to-Electrical Signal Transducing Device.

Stretchable electronic devices that conduct strain-related electronic performances have drawn extensive attention, functioning as mechanical sensors, actuators, and stretchable conductors. Although strain-insensitive or strain-responsive nature is well-achieved separately, it remains challenging to combine these two characteristics in one single device, which will offer versatile adaptability in various working situations. Herein, a hybrid material with sign-switchable Poisson's ratio (SSPR) is developed by combining a phase-change gel based reentrantreentrant honeycomb pattern and a polydimethylsiloxane film. The phase-change gel featuring thermally-regulated Young's modulus enables the hybrid material to switch between negative and positive Poisson's ratios. After integrating with a pre-stretched silver nanowires film, the obtained stretchable device performs bimodal strain-to-electrical signal transducing (Bi-SET) functions, in which the SSPR-dominated strain-resistance response switches between strain-dependent and strain-insensitive behaviors. As a proof of concept, a mode-switchable grasping system is constructed using a Bi-SET device-based controller, enabling the adaptation of grasping behaviors to various target objects.