Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K21: Morphing Matter: From Soft Robotics to 4D Printing IIIRecordings Available
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Sponsoring Units: DSOFT GSNP DPOLY Chair: Emily Davidson, Princeton Room: McCormick Place W-185D |
Tuesday, March 15, 2022 3:00PM - 3:12PM |
K21.00001: Finite Element Modeling of Shapeshifters Daniel G Goldstein We present Morpho, a programmable environment for finite element modeling of shape, including shape optimization and shape shifting. Example applications will be presented for a number of systems from complex fluids to soft robotics. Prospects for further optimization of these systems will be discussed. |
Tuesday, March 15, 2022 3:12PM - 3:24PM |
K21.00002: Morphing flat sheets to 3D curved surfaces with optimal mechanical performance Lishuai Jin, Michael Yeager, Young-Joo Lee, Daniel J O'Brien, Shu Yang The techniques of transforming flat sheets into three-dimensional (3D) curved shapes have emerged as powerful tools to enable a broad range of applications in mechanical and biomedical engineering, robotics, architectures, and science. However, the existing approaches are intrinsically designed to create soft and stretchable structures. Therefore, morphing flat sheets towards curved and conformable geometries while achieving high mechanical strength has not been demonstrated. Here, we report an optimal cutting approach to transform plies of two-dimensional (2D) inextensible yet flexible composite laminate into 3D doubly-curved surfaces with optimized mechanical properties. Guided by a numerical model, the 2D composite plies are rationally tailored, leading to the desired 3D structures with no cut overlapped at the same position among the stacked layers. After consolidation of the plies, the shearing force among the plies can significantly eliminate the effect of the cuts that normally will weaken the mechanical strength of the structures. Our approach opens a fundamentally new paradigm to conform complex shapes of arbitrary curvatures while offering control over the local architecture for lightweight, high mechanical strength. |
Tuesday, March 15, 2022 3:24PM - 3:36PM |
K21.00003: The Role of Symmetry and Patterning in Hierarchical Multistable Metasheets Juan C Osorio, Andres F Arrieta Soft metamaterials have introduced new opportunities for design, programmability, and mechanical computation, by adapting to different input and external stimuli. Recently, dome-patterned metamaterials consisting of patterned array reconfigurable bistable units had gained interest in the scientific community due to their capability of exhibiting different energy minima, hierarchical multistability, and a high dependency in unit cell interactions. As the unit cell architecture can be reversibly inverted at the local scale, programmable multistable shapes and tunable mechanical responses at the global scale are generated due to the local prestress and interaction between each unit. This allows the structure to strongly depend on the unit inversion order and interaction between unit cells, enabling it to exhibit multiple global stable states, including high-energy frustrated states. This work investigates the interrelations between unit cells and spatial arrangement in the hierarchical multistable behavior of patterned metasheets. We examine the possible number of global states by utilizing group theory and isolating the unique pattern configuration to count the coexisting states. |
Tuesday, March 15, 2022 3:36PM - 3:48PM |
K21.00004: Tristable Kirigami Architecture for Mechanical Logic Yi Yang, Douglas P Holmes Shape-morphing structures that could encode memory and perform logic operations are of particular interest to build materials-based physical intelligence and soft robots. To embed memory and perform computing in a mechanical system, the building blocks of the system may contain multiple sets of tunable metastable states. Recently, bistable structures have been employed to show the potential application to serve as two-bits mechanical memory and mechanical logic gates through snapping-through instability. However, the design of various logic gates requires different designs of structural configurations. To simplify the design process, we introduce a single kirigami-inspired tristable architecture that not only encodes mechanical memory but also performs fundamental logic computing. Compared with bistable structures which usually process a double-well potential, this kirigami architecture processes a triple-well potential. Switching between the two local stable states through the additional metastable state produces a variety of mechanical deformations giving rise to multiple fundamental logic operations. Through experiments, simulations, and modeling, we demonstrate the fundamental mechanics and functionalities to leverage the communicative snapping of tristable kirigami architecture for potential applications in mechanical computing. |
Tuesday, March 15, 2022 3:48PM - 4:00PM |
K21.00005: Multimodal locomotion via folding of a degree-four vertex Laura Pernigoni, Davood Farhadi, David Melancon, Antonio M Grande, Katia Bertoldi Folding an origami pattern is governed by simple geometric rules, yet it can lead to a rich behavior that can be exploited in applications ranging from shape morphing to robotics. Here, we show that folding one of the simplest origami building blocks ---a rigid, degree-four vertex--- can lead to locomotion. We first describe how modifying the geometry of the degree-four vertex can lead to different trajectories. We then realize a simple origami-robot capable of moving along arbitrary trajectories by superimposing multiple crease patterns on the same origami sheet and activating/freezing the hinges leading to the desired motion. |
Tuesday, March 15, 2022 4:00PM - 4:12PM |
K21.00006: A machine learning approach to inverse design of programmable liquid crystal elastomers: morphing surfaces Badel Mbanga, Youssef Mosaddeghian Golestani, Michael P Varga, Robin L Selinger Design of liquid crystal elastomer (LCE) devices requires solving an inverse problem: find the nematic director field that morphs a sample to a desired target shape when heated. We present a novel machine learning approach to address the inverse problem for LCE coatings on a rigid substrate, morphing to a target topography[1]. We solve 1500 forward problems via finite element methods [2] for various director configurations to form a training dataset. Next, we train a stacked ensemble regression model using the Autogluon framework [3]. In this autoML solution, multiple modeling methodologies are tried, and an ensemble model is constructed to maximize performance. Hyperparameter tuning is automatically handled by the API. Here 80% of the dataset was used to train the models including tree-based and deep learning algorithms. The prediction of the two parameters defining the director field on the remaining test dataset was evaluated. The ensemble model outperformed any individual model and could also predict configurations that departed from the initial geometry by adding noise. We discuss plans to extend this approach to a broader class of LCE device geometries. [1] Babakhanova 2020 doi:10.1063/5.0022193 [2] Gelebart 2017 doi:10.1038/nature22987 [3] auto.gluon.ai |
Tuesday, March 15, 2022 4:12PM - 4:24PM |
K21.00007: Configuration space engineering: Controlling configuration space topology with geometry Mary Elizabeth Lee-Trimble, Michelle Berry, Christian Santangelo Many complicated systems from proteins to mechanical metamaterials are analyzed by describing them as linkages, or systems of joined bars and pivots. However, the configuration spaces for these mechanisms can be difficult to understand, and critical points, places where constraint counting fails to predict behavior, are surprisingly prolific. In this talk, we present a method for understanding these mechanisms by introducing a tensor field formalism that governs the location of singular points. We will then demonstrate how to use this tensor field formalization to analyze entire classes of mechanisms sharing the same connectivity but different geometries. This gives a geometrical approach to thinking about mechanism design. |
Tuesday, March 15, 2022 4:24PM - 4:36PM |
K21.00008: Configuration space engineering: gating mechanisms by controlling configuration space topology Michelle Berry, David Limberg, Mary Elizabeth Lee-Trimble, Ryan C Hayward, Christian Santangelo A linkage is a mechanical device built from rigid bars and freely rotating joints. Kempe's universality theorem tells us that we can design a linkage with a joint that traces out any algebraic curve we want, but the complexity of the linkage explodes rapidly for even modest complexity curves. In this talk, we approach designing linkages from another angle by designing the topology of the linkage's configuration space. Using a one degree of freedom linkage with a large number of branch points (singularities) in its configuration space as a starting point, we outline how modifications to the linkage change the topology of the configuration space. This gives us the ability to engineer the configuration space of a linkage by picking and choosing which singularities we keep, which ones we remove, and the specific way that we remove them. To demonstrate this process, we connect a linkage with a specifically designed configuration space to a 1D chain of connected rotors and use this additional linkage as a gate to block or allow the propagation of a soliton in the chain. We explore how modifying a small section of the combined linkage can be used to program the motion of the entire structure. |
Tuesday, March 15, 2022 4:36PM - 4:48PM |
K21.00009: How the singing saw gets its voice Suraj Shankar, Petur Bryde, L Mahadevan The ability to sustain notes or vibrations underlies the design of most acoustic devices, ranging from musical instruments to nanomechanical resonators. Inspired by the singing saw that acquires its musical quality from its blade being unusually bent, we ask how geometry can be used to trap and insulate acoustic modes from dissipative decay in a continuum elastic medium. By using experiments, theoretical and numerical analysis, we demonstrate that spatially varying curvature in a thin shell can localize topologically protected modes at inflection lines, akin to exotic edge states in topological insulators. A key feature is the ability to geometrically control both spatial localization and the dynamics of oscillations in thin shells. Our work uncovers a novel mechanism for designing robust, yet reconfigurable, high quality resonators across scales, simply through geometry. |
Tuesday, March 15, 2022 4:48PM - 5:00PM |
K21.00010: Kinetic wavelength selection in an unsupported annulus contracted radially at the inner boundary Anshuman S Pal The prototypical system for studying two-dimensional (2d) wrinkling is the Lamé system – a thin annulus subjected to radial tensile loads at both boundaries so that the material circles wrinkle. The number of wrinkles (i.e. wavenumber) depends on the applied tensile loading or the presence of an external substrate. In [1], we analyse a novel Lamé system: an unsupported annulus that is pulled in only at the inner boundary, and buckles into a radially wrinkled configuration that is developable and hence strain-free. But what sets the system wavelength in the absence of a substrate or tension field? Here, we propose a kinetic mechanism in which the wavelength is set by a combination of dynamic wrinkling wavelengths [2], and wavelength coarsening features called ‘wrinklons’ [3]. We support our claims using finite-element simulations. |
Tuesday, March 15, 2022 5:00PM - 5:12PM |
K21.00011: Morphing with diamonds Maïka Saint-Jean, Etienne Reyssat, Benoit Roman, Jose Bico
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Tuesday, March 15, 2022 5:12PM - 5:24PM |
K21.00012: Soft Kirigami Composite that Deploys into Pre-programmed Shapes Mohammad Khalid Jawed, Mrunmayi Mungekar, Vishal Kackar, Shyan Shokrzadeh, Leixin Ma, Wenzhong Yan, Vwani Roychowdhury We report soft composites with multiple layers that morph from a planar form into pre-programmed 3D shapes. We start with bilayered composites wherein a pre-stretch is applied to a substrate layer; an unstretched layer is then attached on top of the same. The applied pre-stretch leads to a strain mismatch between the two layers, which forces the planar composite structure to assume a 3D shape when the load is released. Inspired by kirigami, the top layer is cut along specific patterns that ultimately determine the shape of the final 3D structure. We focus on the kirigami pattern that leads to a hemispherical 3D shape. Furthermore, we compare experiments with finite element simulations. We study the effect of various parameters, namely, kirigami pattern, amount of strain mismatch, and geometrical and material properties of the layers, on the shape of the final structure. This project is an unprecedented attempt at form-finding in mechanics through the combination of strain mismatch and kirigami patterning. Notably, the entire fabrication process of the 3D structure takes place on a 2D plane. Due to this ease of manufacturing, soft kirigami composites can find application in wearable electronics, deployable aerospace structures, and soft robotics. |
Tuesday, March 15, 2022 5:24PM - 5:36PM |
K21.00013: Two-photon Printing of Polymer Networks with Circular Dichroic Memory Madelyn P Jeske, Mitchell Anthamatten Metamaterial structures are fabricated with periodic length scales below incident light wavelengths, imparting properties that were not present in the bulk state such as negative Poisson ratio or negative refractive index. With an interest in further miniaturizing adaptive metamaterials, we hereby report on the high resolution, two-photon polymerization (2PP) of a thiol-vinyl shape-memory resin which exhibits shape-memory at the microscale. The glassy network is designed to have a trigger temperature (Tg) at 60 °C whereby it transforms into a rubbery network. These materials can be printed using 2PP at high resolution, with features beneath 500 nm, and are capable of being printed into a metamaterial lattice that displays circular dichroism. The metamaterial can be compressed and cooled to temporarily disrupt its metastructure and its corresponding circular dichroism. Upon reheating, the original structure is recovered along with its circular dichoism. These results open the door to designing metastructures with interplay between mechanics and light. |
Tuesday, March 15, 2022 5:36PM - 5:48PM |
K21.00014: Shape fluctuations of fluidized vesicles driven by dilute active nematics. Sarvesh Uplap, Michael F Hagan, Aparna Baskaran, Alfredo Sciortino, Hammad Faizi, Andreas R Bausch, Petia Vlahovska, Zvonimir Dogic Motivated by recent experiments on the microtubule-kinesin active nematics confined in vesicles, we study a microscopic particle-based model of semiflexible polymers with nematic activity confined in fluid vesicles. Using Brownian dynamics simulations, we characterize the emergent behaviors as a function of control parameters including filament length, vesicle size, and rigidities of the filaments and vesicles. We find that the interplay between internal active stresses from the enclosed filaments, the elasticity and fluidity of the confining vesicle leads to novel emergent filament organizations not seen in other active matter systems, as well as interesting transformations of the vesicle shapes and dynamics. In particular, the resulting vesicle shape fluctuations exhibit clear non-equilibrium signatures. We compare predicted vesicle shape fluctuation correlation functions with those measured in experiments. Moreover, in the simulations we find correlations between vesicle fluctuations and the spatiotemporal organization of enclosed filaments, which may enable inferring filament organizations in the experimental results. This study elucidates physical mechanisms that underlie diverse cellular biophysical phenomena that involve membrane shape transformations. |
Tuesday, March 15, 2022 5:48PM - 6:00PM |
K21.00015: Osmosis-driven, non-vascular-plant-inspired soft composites Shelby Hutchens, Amrita Kataruka Even without the aid of muscle, plant tissue drives large, forceful motion via osmosis-driven fluid flow. In this work, we demonstrate that a synthetic, plant tissue analog (PTA) can mimic the closed-cell structure and osmotic actuation of non-vascular plant tissue, enabling the emergence of turgor-pressure-induced stiffness and leading to more forceful swelling deformations. PTAs consist of micron-sized saltwater droplets embedded within thin, highly stretchable, selectively-permeable polydimethylsiloxane PDMS walls. When immersed in water, these PTAs reach a state of equilibrium governed by the initial osmolyte concentration (higher produces more swelling) and cell wall mechanical response (stiffer and less stretchable yields less swelling). These structures represent an alternate class of aqueous, autonomous synthetic materials that, like hydrogels, may be useful in biomedical applications. However, unlike hydrogels, which soften upon swelling, PTA turgor-driven actuation supports much larger loads, even for similar modulus initial states in these highly hydrated classes of soft materials. |
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