Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M07: Functionality through Nonlinearity in MetamaterialsFocus
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Sponsoring Units: DSOFT Chair: Shravan Pradeep, University of Pennsylvania; David Melancon, Ecole Polytechnique de Montreal Room: Room 130 |
Wednesday, March 8, 2023 8:00AM - 8:36AM |
M07.00001: Computations with flexible metamaterials Invited Speaker: Martin van Hecke Bistable beams, controlled by buckling and snapping nonlinearities, naturally act as mechanical bits. The central tenet of this talk is that interactions between such bits allow flexible (meta) materials to store and process information. I will discuss metamaterials that count how often they are compressed and that can select and process input strings composed of complex compression cycles. These materials can be mapped to finite state machines so that their computation power can precisely be characterized. This work shines new light on the nonlinear response of complex materials and opens the door to 'intelligent matter'. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M07.00002: Exotic Properties Enabled by a Mechanical Metamaterial that Contracts Under Increasing Tension Paul Ducarme All known materials and structures elongate in response to an increasing tensile force. Recently it has been suggested that this behavior is not inevitable: a sudden and finite contraction under an increasing quasistatic tension load could theoretically be observed in a nonlinear mechanical network satisfying a Wheatstone bridge topology. Inspired by this theoretical prediction, we design and manufacture a mechanical structure that displays this counter-intuitive phenomenon. The design is obtained by combining modular building blocks made of an elastic material. Each building block exploits geometric nonlinearities to show either a softening, stiffening or nonmonotonic tensile mechanical response. We then develop a numerical tool to investigate the collective behavior of assemblies made of these building blocks, which guides us towards the final design. Our work uncovers the design principles to build a structure that contracts under tension and brings to light potentially useful associated properties, thereby further expanding the design space for smart structures, MEMS and mechanical metamaterials that could harness these novel mechanical behaviors to achieve advanced functionalities. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M07.00003: Multistable machines with mechanical sensing capabilities Leon Kamp, Benjamin Gorissen, Mohamed Zanaty, Ahmad Zareei, Katia Bertoldi Multistable structures have emerged as a powerful platform to program sequences and enable new functionalities, ranging from multimodal deformation to logic gates. By programming functionalities in a nonlinear energy landscape, performance can be preserved with fewer components, and without dedicated control of each degree of freedom. Here, we present a strategy to realize multistable structures with a tunable energy landscape to allow for a wide range of deformation sequences. More specifically, our building block consists of a four-bar parallelogram mechanism that connects two rectangular blocks with a pair of identical levers. We span an elastic rubber band between the blocks to create a multiwelled energy landscape that can be tuned by simply varying the anchor point of each elastic band. The stacking of multiple of these building blocks leads even more rich behavior, which is used to create a robotic crawler that combines motion sequencing with mechanical sensing capabilities. As such, this demonstrator can autonomously react to triggers from its the surrounding environment. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M07.00004: The collective snapping of competing buckled beams Lennard Kwakernaak, Martin van Hecke, Arman Guerra Slender structures are crucial for the design of non-linear mechanical metamaterials. Here we study the collective snapping of buckled beams in contact, and obtain a novel transition between two distinct snapping regimes. We demonstrate the fundamental nature behind this transition and how it can be exploited for implementing sequential behavior, counting and information processing in mechanical metamaterials. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M07.00005: Connecting the Branches of Multistable Non-Developable Origami Using Crease Stretching Andres F Arrieta, Clark Addis Reconfigurable origami systems show great promise for expanding the functionality of adaptive structures. However, the myriad folding pathways makes it difficult to control the trajectory during reconfiguration. Multistable origami systems simplify the control problem, however they rely on flexible and stretchable facets to resolve geometric frustration. This excludes materials that cannot accommodate large strains, including electronics based on brittle semi-conductors. Traditional origami methods have been used to achieve multiple stable states without facet stretching, but rely on precise relative tuning of the crease stiffness. By relaxing the requirement that the system be folded from a flat sheet of paper, so called “Non-Euclidian Origami” has achieved multiple stable states with the use of a single torsional spring. Specifically, for a 4-facet origami system, it has been shown that these stable states lie on two disconnected branches. In this work, we take a 4-facet origami system and permit crease stretching in addition to bending to enable the continuous folding between these otherwise disconnected branches. The crease stretching, or Spring Origami, is inspired by the wing deployment mechanism in the Earwig. Using spherical geometry, we develop a mapping between the kinematic space and the energetic space of the 4-facet origami system. We show that a single 4-facet origami unit can exhibit up to 3 stable states, with 2 distinct folding pathways between each state. This analysis provides a simple analytic method to predict which equilibrium angles which result in mono-, bi-, tri-stable behavior. Ultimately, we lay the groundwork for controlling the folding pathways and stable shapes of stiff reconfigurable origami systems without additional control complexity. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M07.00006: Defect engineering of nonlinear wave propagation in bistable mechanical lattices Piyush Grover, Mohammed A A Mohammed
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Wednesday, March 8, 2023 9:36AM - 9:48AM |
M07.00007: Exploiting Buckling-induced Symmetry Breaking for Tunable Wave Propagation through Elastic Phononic Crystals Tejas Dethe, Alison Root, Andrej Kosmrlj Elastic phononic crystals (EPC) are metamaterials that have periodic modulations in material properties such as shear modulus, bulk modulus, and density, while being flexible to deformations. In EPCs, wave propagation is affected not only by material properties but also by symmetry properties of the crystal. In the past, it has been shown that buckling of compressed EPCs could tune wave propagation – for example, by changing the number of intersections in the band diagram, potentially leading to the opening of band gaps. From the theoretical standpoint of representation theory of symmetry groups, we can trace such changes in band diagrams to changes in symmetries of deformed phononic crystals. This helps us predict, which band intersections are protected by symmetry and their degree of degeneracy. We anticipate that buckling, in addition to causing a state of stress in the EPC, also leads to a change in the unit cell symmetry. In this work, we take a closer look at buckling-induced symmetry breaking and extend the representation theory formalism for different loading conditions. We then have the potential to predict how different loading paths affect the symmetries of EPCs and hence their wave propagation properties, which would be helpful for a rational design of tunable EPCs. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M07.00008: Symmetry Breaking via Buckling in a Soft Piezoelectric Phononic Crystal Alison Root, Tejas Dethe, Andrej Kosmrlj A soft phononic crystal can be the basis for a two state phononic device, as under compression the crystal will buckle and come to a second geometric state with new crystal symmetry and therefore new phononic properties. There are many interesting applications and extensions to this system that can be explored for more exotic device functionalities. Piezoelectric phononic crystals (PPCs) are of interest for their ability to have surface acoustic waves actuated by transducers embedded in the crystal, and soft PPCs may have some unique properties under deformation but are relatively unexplored. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M07.00009: Nonreciprocity via nonlinearity-enabled all-acoustic spatiotemporal modulation Jihad Alqasimi, Kai Qian, Nicholas Boechler Acoustic nonreciprocity has attracted attention for its potential in designing logic devices. One way to break reciprocity is by breaking the time-reversal symmetry by spatiotemporally (ST) altering a system's material properties. In the present study, we derive the equations of motion for a discrete non-linear spatiotemporal modulated spring mass system, where the shear stiffnesses are non-linearly dependent on the longitudinal deformations, and produce a physical realization of such a system. We also provide the geometric design with constraints such that we can control the relative speed and coupling strength of the longitudinal and shear waves, as well as the nonreciprocal band structure. Finally, we will present experimental measurement and numerical simulations of nonrecirpocal acoustic wave propagation in this system. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M07.00010: Analytic characterization and control of nonlinear nonuniform boundary modes in isostatic systems Michael D Czajkowski, Zeb Rocklin Lattices with balanced numbers of mechanical degrees of freedom and constraints (called Maxwell, mechanically critical or isostatic) acquire rigid, zero-energy modes from absent bonds at their boundaries. While some uniform nonlinear and spatially varying linear modes of such lattices have been characterized analytically, the nonuniform, nonlinear reference states which they are hypothesized to contain remain largely uncharted. Here, we show analytically that the nonlinear boundary modes for the classic example of the Kagome lattice may be understood to correspond with the conformal, or angle-preserving, maps and we further present an algorithm to generate these configurations. This observation enables the construction and numeric confirmation of a unique elastic energy functional which displays the signature of a recently identified structural duality, along with bulk-boundary correspondence which enables the zero energy deformations to be activated using boundary control. We further introduce a diagram-based approach to reveal an infinite, but subextensive, number of uniform collapse pathways. We find that all of these pathways are pure-dilational, suggesting the continued role of the conformal maps, and overall bringing the complete characterization and control of the zero energy deformation pathways of this lattice into view for the first time. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M07.00011: Novel re-entrant transition as a bridge of broken ergodicity in confined monolayers of hexagonal prisms and cylinders Prajwal Bangalore, Fernando A Escobedo Monte Carlo simulations were used to study the entropy-driven monolayer assembly of hexagonal prisms and cylinders under hard slit confinement. At the conditions investigated, the particles have two distinct dynamically disconnected rotational states: unflipped and flipped, that cast distinct projected areas over the wall plane that favors either hexagonal or tetragonal packing. Our simulations revealed a re-entrant melting transition where a disorder Flipped-Unflipped (FUN) phase is sandwiched between a fourfold tetratic phase at high concentrations and a sixfold triangular solid at intermediate concentrations. The FUN phase contains a mixture of flipped and unflipped particles with high translational and rotational mobility. Complementary experiments with fabricated cylindrical microparticles confined in a wedge cell validated the formation of the simulated phases with a comparable fraction of flipped particles and structures, i.e., the FUN phase, triangular solid, and tetratic phase, indicating that both experiments and simulations approach sample analogous basins of particle-orientation phase-space. We also investigated the role of entropic forces on the re-entrant phase behavior by varying particle aspect ratio, (i.e., the ratio of circular face diameter to height of the particle). |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M07.00012: Multistable self-folding knit architectures for soft switches Kausalya Mahadevan, Vanessa Sanchez, Helen E Read, Katia Bertoldi Multistability – the property of having multiple stable equilibrium configurations – has recently emerged as a powerful platform to design a wide range of smart structures, including logic gates, transformable architectures and energy absorbing systems. In thin composite shells, conflicting stresses between layers provide a robust way to encode bistability. However, this typically requires the tedious assembly of layers while they are under strain. Here, we show that the weft knitting process intrinsically introduces differential internal stresses into the fabric and we exploit these stresses in periodic and non-periodic patterns to achieve multistability. |
Wednesday, March 8, 2023 10:48AM - 11:00AM |
M07.00013: Exploration of the Energy Landscape of Knitted Fabrics for Mechanical Programmability Xiaoxiao Ding, Christopher H Rycroft Knitted fabrics exhibit richness in their energy landscapes, which can be exploited for a wide range of engineering applications from wearable mechanical metamaterials to soft robotics. We use a physically validated and efficient numerical tool to calculate the strain energy landscape of knitted materials. We first show that a wide range of elastic energy states can be achieved by varying the structural unit cells. Then, we examine the anisotropy of fabric by performing a parametric study on loading conditions. Our results allow us to explore the design space of knitted materials and find structures with mechanical responses that are tailored to different applications. |
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