Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M16: Infomatter: Discovery and Design of Memory Formation and Information in MatterFocus
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Sponsoring Units: DSOFT Chair: Nathan Keim, Pennsylvania State University; Joseph Paulsen, Syracuse University Room: Room 208 |
Wednesday, March 8, 2023 8:00AM - 8:36AM |
M16.00001: Memory and aging via coupled elastic instabilities in thin crumpled sheets Invited Speaker: Yoav Lahini Crumpling an ordinary thin sheet transforms it into a complex structure with unusual mechanical behaviors, such as enhanced rigidity, emission of crackling noise, slow relaxations, and a range of mechanical memory effects. We describe research focused on understanding these emergent behaviors, reminiscent of those exhibited by glassy systems, and their relation to the geometrical structure of the crumpled sheet. |
Wednesday, March 8, 2023 8:36AM - 9:12AM |
M16.00002: Mechanical cognition across scales Invited Speaker: Marc Serra-Garcia Elastic structures span a broad range of properties, from extremely linear to higly nonlinear, deterministic to stochastic and om overdamped to ultracoherent. In spite of this richness, mechanics as an information-processing platform is still in its infancy. In this talk, I will review our recent work on mechanical information processing in structures ranging from centimeter scale soft robots to nanometer-sized micromechanical logic gates. Each of these scales is both a window to a different type of physics (viscoelasticity, cracks, geometric nonlinearity, stochastic thermodynamics), and an opportunity for different applications. However, on a fundamental level, these systems are described by equivalent equations and therefore amenable to similar design techniques. As highlight applications, I will discuss our soft robotic designs that execute graph search algorithms to find the exit of a maze, nananomechanical logic gates that approach thermodynamic limits, and a passive elastic structure that can distinguish between spoken commands. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M16.00003: Emergent computing in a non-Abelian metamaterial Amitesh Singh, Margot Teunisse, Matthieu Labousse, Martin van Hecke An elastic material that follows the linear laws of elasticity is impervious to the order of actuations due to superposition, severely constraining the design of programmable metamaterials. Here, we introduce a non-Abelian metamaterial sensitive to the sequential ordering of mechanical actuation signals as well as to the magnitude of such actuations. We demonstrate how to describe these materials as finite state machines and boolean logic circuits, encoding different flavours of one-bit memory in a single unit cell. We present a scalable framework to study such materials to understand and utilize their rich and complex behaviour. Our work sets the groundwork for multifunctional designer matter with memory. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M16.00004: Controlling subharmonic orbits by coupling subharmonic units Colin Meulblok Slender elements play the role of material bits in multistable and programmable metamaterials. Despite tremendous progress we currently have limited control over the sequential response under cyclic driving. Here we present a general bottom-up strategy to realize sequential metamaterials in which the transient and subharmonic response to cyclical driving can be controlled and designed. We demonstrate simple two-element metamaterials with period two, three and four, and outline how the subharmonic and transient response can be extended in larger systems. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M16.00005: Competition Between Energy and Dynamics in Memory Formation Varda Faghir Hagh, Chloe W Lindeman, Chi Ian Ip, Sidney R Nagel Hysterons and their interactions can be used as a simple model to study memory formation in cyclically driven materials. The default hysteron model is based on a double-well potential with two adjacent energy minima that are typically treated quasistatically. In this talk, I will introduce a generalized hysteron model with tunable bi-stability that can serve as a model for understanding memory in systems with inherent dynamics. Changing the timescale of the driving in this model allows the system to transition between a situation where its fate is determined by following the local energy minimum to one where it is trapped in a shallow minimum determined by the path it takes. Oscillatory forcing can lead to transients lasting many cycles, a behavior not possible for a single quasistatic hysteron. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M16.00006: SnapGami: frustrated sheets with controllable pathways Lishuai Jin, hadrien bense, Martin van Hecke Crumpled sheets and amorphous media alike are geometrically frustrated systems, which under slow driving exhibit sequences of hops between their metastable states. These rearrangements encode memory effects as well as emergent computing but are difficult to control due to the highly disordered and uncontrolled geometry of these systems. Here we introduce an experimental platform that combines the geometric control of origami with the multistability of frustrated sheets, and which allows (to precisely and reproducibly) control and couple multiple bistable hysteretic elements: snappigami/crumpigami. We demonstrate that the geometry of the origami controls the switching thresholds, while the relative positions of the bistable elements set their interactions, giving rise to pathways inaccessible to systems of independent hysterons. Our work opens a new way for origamis with path-dependent behaviors. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M16.00007: Isolating the Enhanced Memory Capacity of a Glassy System Travis Jalowiec, Nathan C Keim Recent studies of glassy materials have shown how cyclic deformations can form memories of strain. We explore how choices of preparation and driving protocol can reveal dramatically different aspects of a system's memory capacity. We simulate a system of multiple rearranging soft spots subject to cyclic shear, modeled as hysterons. For hysterons with cooperative (ferromagnetic) interactions, symmetric driving (e.g. both positive and negative shear strain) reveals a return-point memory of multiple strains observed previously in experiments and molecular dynamics simulations. By contrast, asymmetric driving (e.g. only positive shear strains, or only compressive loading) prevents these memories. However, when frustrated interactions are introduced, a different mechanism takes the place of return-point memory and restores the capacity for multiple values. Our work suggests that this more robust form of memory can be a leading-order signature of frustration. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M16.00008: Probing the role of frustrated interactions in experiments with an amorphous solid Zhicheng Wang, Nathan C Keim In an amorphous solid that has been mechanically annealed, small plastic deformations cause local groups of particles to reversibly switch between two states. This mechanism supports the generic behavior known as return-point memory, which allows the strain(s) of past deformations to be read out. In general, pairs of rearranging regions may have frustrated (antiferromagnetic) interactions, leading to deviations from return-point memory. However, it has been unclear whether these deviations could be large enough to be identified in experiments. In our experiments, we cyclically shear a soft, frictionless amorphous solid composed of bidisperse colloidal particles at an oil-water interface. We report on tests that use asymmetric shear and amplitude variation to clearly distinguish the effects of frustration from return-point memory and noise. Our results are an estimate of the importance of frustrated interactions in an annealed amorphous solid. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M16.00009: Angle of applied shear: a new knob for probing rearrangements in jammed packings Chloe W Lindeman, Sidney R Nagel Jammed packings live in complex energy landscapes that can be explored by applying an external strain, for example shear. With repeated cycles of such strain, packings begin to go through the same series of particle rearrangements over and over. However, these cycles and rearrangements have typically been studied using only simple shear, which corresponds to just one possible constant-volume deformation. Here we measure the response of packings to shear applied at all angles. In the limit of linear response, we recover a shear modulus that depends sinusoidally on angle, consistent with [1]. For finite strain, we find that individual rearrangements are surprisingly robust to a change in shear angle, sometimes persisting for nearly 90 degrees. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M16.00010: Memory in aging colloidal gels with time-varying attraction Yihao Chen, Qingteng Zhang, Subramanian Ramakrishnan, Robert L Leheny We report a study of gel formation and aging in suspensions of nanocolloidal spheres with a short-range attraction whose strength is tuned by changing temperature (T). Following a quench to a T below the gel point, the suspensions form gels that age through an increasing elastic shear modulus (G') and slowing, increasingly constrained microscopic dynamics. When the attraction strength is suddenly decreased during aging, the gel properties evolve non-monotonically like in the Kovacs effect in glasses, in which G' decreases and the microscopic dynamics become less constrained for a period before more conventional aging resumes. Eventually, the properties converge to those of a gel that has undergone aging at the lower attraction strength throughout. The time scale of the convergence increases as a power law with the age at which the attraction strength is decreased and decreases exponentially with the magnitude of the decrease. A model for gel aging in which particles attach and detach from the gel at rates that depend on their contact number qualitatively reproduces these trends and reveals that the non-monotonic behavior results from the dispersion in the rates at which the populations of particles with different contact number adjust to the new attraction strength. |
Wednesday, March 8, 2023 10:48AM - 11:00AM |
M16.00011: Training soft magnetoelastic nanoparticle sheets Edward P Esposito, Hector Lopez-Rios, Monica Olvera De La Cruz, Heinrich M Jaeger Ideal materials for reconfigurable mechanical microstructures would be manipulable by external fields, and would be trainable into a particular state once the external field were released. Our experiments use ~10nm thick membranes of self-assembled superparamagnetic nanoparticles. The membranes' thinness and inherently soft elastic properties allow micron-scale deflections, which we track and image with high-resolution confocal microscopy. Under typical conditions, the membrane's deflection is elastic, so that membranes deflected by a magnetic field recover their initial neutral configuration when the field is released. However, by subjecting them to heating while deflected in the field, we can cause them to retain their deflected configuration once the field is released, with reduced flexibility in the new state. Later subjecting them to an excess of humidity, we can cause them to recover their initial neutral configuration as well as their initial flexibility. We use molecular dynamics simulations of the nanoparticle sheets to predict the deflected configuration in various applied magnetic fields, and to understand the general magnetoelasticity of this system. Combining magnetism and soft elasticity with training effects in this way, magnetoelastic nanoparticle membranes are thus a promising platform for reconfigurable mechanical microstructures. |
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