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On‐water rowing is a sport where participants make extensive, powerful, and complex repetitive movements with their wrists to pull and feather (twist) the oar. Herein, the aim is to assess the frequency and perceived causes of wrist and forearm pain in rowers and, in particular, assess whether there are any possible mechanical issues that could be addressed through the use of auxetic technology. Through an online survey of 145 on‐water rowers, it is found that 33.8% of the rowers reported wrist or forearm pain arising from rowing. The majority (67.3%) consider over‐gripping to be the cause while one out of five associated it with periods of tension and anxiety, which also led them to over‐grip. This indicates that rowing handles could benefit from the use of mechanical metamaterials, auxetics in particular, owing to their anomalous manner in how they deform when subjected to mechanical deformations. Moreover, given the rise in popularity of coastal rowing, which will become an Olympic discipline alongside classic rowing as from the 2028 Los Angeles Olympic Games, the potential use of auxetics in the manufacture of protective gear for use in coastal rowing is also discussed. [ABSTRACT FROM AUTHOR]

Novel mechanical metamaterials inspired by single crystal boron arsenate built at the macroscale using conventional materials are presented and investigated through finite element simulations. It is shown that these mechanical metamaterials can mimic, to some extent, the properties of boron arsenate with the more robust rotating rigid‐units mechanism being excellently replicated and even made to operate more efficiently through modifications of the geometry of the mechanical metamaterial. It is also shown that not all mechanisms causing auxeticity at the nanoscale can be upscaled due to the absence of the appropriate interactions at higher length scales. This confirms that already existing materials, which have been adequately characterized and studied, can prove to be a very useful source of information for the design of novel mechanical metamaterials which can exhibit even more auxetic properties than the original material itself. [ABSTRACT FROM AUTHOR]

Boron arsenate, BAsO4, is a β-cristobalite-like crystal which has been reported to exhibit the rather unusual property of negative linear compressibility behaviour at elevated pressures, that is expanding rather than shrinking in a linear dimension when subjected to pressure. This work proposes a 'geometry—deformation mechanism'-based mathematical model to aid the discernment of the manner how this anomalous pressure behaviour is achieved. The model makes use of data obtained from DFT simulations over an extended range of pressures, including extreme pressure conditions, and rigorously explains the macroscopic properties of this material in terms of the nanoscale deformations. More specifically, through this model, it was possible to decipher the different contributions to the deformation mechanism and compressibility properties of BAsO4. Moreover, for the first time, it was shown that a rule related to the sum of angles of tetrahedrally coordinated atoms is so robust that it applies at the extreme pressures studied here. [ABSTRACT FROM AUTHOR]

Auxetics display the anomalous property of expanding laterally when uniaxially stretched, that is, a negative Poisson's ratio, a property that arises from 1) the presence of specific geometric features within the nano/macrostructure of the material and 2) amenable deformations in response to the applied stimulus. Herein, how ancient symmetrical esthetic artifacts have been transformed to functional auxetics through mechanisms that have ripened the field of "mechanical metamaterials" and "architected materials" in the last decades is explored. In particular, the important role and various implementations, both in 2D and 3D, of "rotating rigid units," which range from "rotating squares" to much more complex renditions at various scales of structure, are looked at. The role of rotating rigid units to generate negative thermal expansion and negative compressibility is also delved into. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials represent a class of deformable systems, which exhibit macroscopic deformations, mechanical, and/or thermal properties. These emerge due to the structure of their subunits rather than their materials composition and typically exhibit anomalous (normally negative) macroscopic structural, mechanical, or thermal property/properties caused by a change in shape/size of the system. Herein, a class of honeycombs is discussed, which push to the extreme the classical definition of "mechanical metamaterials," exhibiting temperature‐tunable Poisson's ratio properties. More specifically, centrosymmetric honeycombs with T‐shaped joints constructed from different materials are shown to exhibit temperature‐dependent Poisson's ratio values, which can be either positive or negative (auxetic) depending on the external stimulus the system is subjected to. The sign and magnitudes of the Poisson's ratio values are explained in terms of particular geometries that these composite honeycomb systems attain at different temperature conditions. In particular, auxeticity is attributed to the transformation of the T‐shaped units to re‐entrant units. Practical aspects on how these properties may be achieved are discussed, including the possibility that the changes in shape, and hence Poisson's ratios, are induced via different extents of dryness on opposite surfaces of ligaments made from absorbent materials. [ABSTRACT FROM AUTHOR]

A novel mechanism is identified leading to negative linear compressibility (NLC) in boron arsenate which is shown to arise from deformations in the framework tetrahedra rather than more conspicuous tetrahedral rotations. Instead, such rotations, which manifest as "rotating squares" when viewed down the c direction, are found to result in negative Poisson's ratio (NPR) in the (001) plane, which in turn augments the compressibility, a phenomenon that should be applicable to other auxetic materials. It is hypothesized that the generic NLC and NPR mechanisms identified here, as well as the augmented compressibility due to auxeticity should also feature in materials and metamaterials with similar characteristics. [ABSTRACT FROM AUTHOR]

Poly(phenylacetylene) sheets that mimic the geometry of a wine-rack-like structure have been predicted to exhibit negative Poisson's ratios off-axis. However, their potential to exhibit negative linear compressibility (NLC) has remained largely unexplored. In this work, the compressibility and other mechanical properties of wine-rack-like poly(phenylacetylene) networks with 1,2,4,5 tetra-substituted phenyls as well as their equivalent with allene or cyclobutadiene centres are simulated to assess their ability to exhibit negative linear compressibility on-axis and off-axis. It is shown that some of these systems can indeed exhibit negative linear compressibility whilst others exhibit a near-zero compressibility. The results are compared to the compressibility properties of other poly(phenylacetylene) networks reported in literature as well as with those predicted from the analytical model for an idealised wine-rack structure deforming through hinging. Results suggest that these mechanical properties are arising from a wine-rack-like mechanism, and there is a good agreement with the theoretical model, especially for systems with longer acetylene chains whose geometry is closer to that of the idealised wine-rack. [ABSTRACT FROM AUTHOR]

The re-entrant honeycomb microstructure is one of the most famous, typical examples of an auxetic structure. The re-entrant geometries also include other members as, among others, the star re-entrant geometries with various symmetries. In this paper, we focus on one of them, having a 6-fold symmetry axis. The investigated systems consist of binary hard discs (two-dimensional particles with two slightly different sizes, interacting through infinitely repulsive pairwise potential), from which different structures, based on the mentioned geometry, were formed. To study the elastic properties of the systems, computer simulations using the Monte Carlo method in isobaric-isothermal ensemble with varying shape of the periodic box were performed. The results show that all the considered systems are isotropic and not auxetic—their Poisson's ratio is positive in each case. Moreover, Poisson's ratios of the majority of examined structures tend to + 1 with increasing pressure, which is the upper limit for two-dimensional isotropic media, thus they can be recognized as the ideal non-auxetics in appropriate thermodynamic conditions. The results obtained contradict the common belief that the unique properties of metamaterials result solely from their microstructure and indicate that the material itself can be crucial. [ABSTRACT FROM AUTHOR]

In this work, through the use of a theoretical model, we analyse the potential of a specific three-dimensional mechanical metamaterial composed of arrowhead-like structural units to exhibit a negative Poisson's ratio for an arbitrary loading direction. Said analysis allows us to assess its suitability for use in applications where materials must be able to respond in a desired manner to a stimulus applied in multiple directions. As a result of our studies, we show that the analysed system is capable of exhibiting auxetic behaviour for a broad range of loading directions, with isotropic behaviour being shown in some planes. In addition to that, we show that there are also certain loading directions in which the system manifests negative linear compressibility. This enhances its versatility and suitability for a number of applications where materials exhibiting auxetic behaviour or negative linear compressibility are normally implemented. [ABSTRACT FROM AUTHOR]