Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C07: Morphing Matter: From Soft Robotics to 4D PrintingFocus Live
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Sponsoring Units: DSOFT GSNP Chair: Andrej Kosmrlj, Princeton University Room: 07 |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C07.00001: Programming stiff inflatable shells from planar patterned fabrics Emmanuel Siefert, Tian Gao, Jose Bico, Etienne Reyssat, Benoit Roman We introduce a versatile single-step method to shape-program stiff inflated structures, opening the door for numerous large scale applications, ranging from space deployable structures to emergency shelters. This technique relies on channel patterns obtained by heat-sealing superimposed flat quasi-inextensible fabric sheets. Inflating channels induces an anisotropic in-plane contraction and thus a possible change of Gaussian curvature. Seam lines, which act as a director field for the in-plane deformation, encode the shape of the deployed structure. We present three patterning methods to quantitatively and analytically program shells with non-Euclidean metrics. |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C07.00002: Micron sized kirigami robots - Design and inverse design Itay Griniasty, Himani Sinhmar, Qingkun Liu, Wei Wang, Hadas Kress-Gazit, James Patarasp Sethna, Itai Cohen While it is well known how to design the tesselation of a single Kirigami sheet such that it transforms into one target shape, here we propose to design a sheet that can transform into any desired shape for applications in in robotics. Specifically, we study foldable microscopic sheets that change their shape in response to digitized electronic signals. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C07.00003: Shape change through elastic phase-separation Emmanuel Siefert, Benoit Roman, Jose Bico, Etienne Reyssat We observed an unexpeted instability in an architected elastomer plate that includes an internal network of airways (”baromorph”). |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C07.00004: Inflatable grippers Ignacio Andrade-Silva, Joel Marthelot The coupling between elasticity and geometry in pressurized structures can lead to unexpected deformations. Elastic curved tubes made of two flat quasi-inextensible thin sheets sealed together respond in such a way that their reference curvature is amplified when they are inflated. Here we focus on V-shaped tubes with sharp corners that deform so the initial angle between the arms decreases upon inflation, acting as a hinge-like mechanism. We first characterize the kinematic and the mechanical response of an individual hinge through a combination of experiments and finite element modelling. This observation serves as a starting point for exploring several mechanism designs. We propose a star-shaped tube made of successive V-shaped tubes forming a closed loop as a mechanical actuator. Upon inflation, the structure contracts radially and provides a soft grasping solution with tunable grabbing force. Building on the mechanical description of individual hinges, we address the inverse problem and optimize the geometry of the closed loop and operational conditions to obtain a target grabbing force for the gripper. |
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C07.00005: Oscillating Membranes: Controlling Autonomous Shape-transforming Sheets Ido Levin, Robert D Deegan, Eran Sharon Imposing residual stresses on thin structures is an established mechanism to induce global shape changes. Living organisms have mastered the dynamic control of these residual stresses to induce shape transformation and locomotion. By comparison, man-made implementations are rudimentary. Here we present the first autonomously shape-shifting soft sheets and show that these have the potential to achieve the locomotive capabilities of living organisms. The sheets are made of a gel that shrinks and swells in response to the phase of an oscillatory chemical (Belousov-Zhabotinsky) reaction. Propagating reaction-diffusion waves of the reaction induce localized shrinking or swelling of the gel resulting in time-periodic global shape changes, for example flapping. We present the computational tools and experimental protocols needed to control this system, principally the relationship between the curvature of the sheet and the reaction phase, and optical imprinting of the wave pattern. This quantitative control marks an important step towards the realization of autonomous soft machines. |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C07.00006: Morphing LCE surface coatings with topological defects: simulation studies Robin Selinger, Youssef Mosaddeghian Golestani, Jonathan Selinger, Sajedeh Afghah, Michael P Varga Stimuli-responsive liquid crystal elastomers (LCE) with patterned molecular orientation morph in response to any stimulus that affects nematic order. We model shape-morphing in temperature-responsive dynamic thin film coatings with patterned disclinations oriented either parallel or perpendicular to the surface normal. For short disclinations perpendicular to the surface, we find that arrays of +/- 1 defects give rise to profiles with dimples or spikes depending on whether defects are radial or azimuthal. By altering defect core structure we design a flat coating that transforms to an array of suction cups resembling octopus suckers, e.g. to create temperature-driven adhesion. We also model LCE coatings with disclinations parallel to the surface, formed between substrates with antagonistic anchoring patterns. We model formation of the resulting microstructure under antagonistic alignment, and morphing of the coating on heating to form an array of microchannels. We compare theory and modeling studies with recent experiments [1-2] and discuss potential applications. [1] Babakhanova et al Nat Commun 9, 456 (2018). [2] Babakhanova et al, Journal of Applied Physics, in press. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C07.00007: Using Bifurcation theory to instruct design of Magneto-Elastic Machines Itay Griniasty, David Hathcock, Teaya Yang, Yuchao Chen, James Patarasp Sethna, Itai Cohen A major hurdle in designing origami and kirigami based microscale machines is achieving complex functionality with simple sheet designs. We address this problem using magneto-elastic machines: sheets comprised of rigid magnetic panels connected by elastic hinges that fold into equilibrium conformations. To function, such machines need to transform between multiple conformations. Shape transformation is achieved through small variations in the hinge rest angles. These variations, however, typically lead to small conformation changes that are devoid of function. We solve this problem by designing such machines next to bifurcations in the magneto-elastic dynamics, where multiple distinct states are accessible by small changes in the system parameters. The difficulty with this approach is that the higher the order of the bifurcation, the more difficult it is to find magnetic patterns that lead to the corresponding dynamics. To find these rare patterns, we adapt a continuation algorithm that follows bifurcations of growing order along a one dimensional curve in the system's multidimensional phase space. We demonstrate our approach with a macroscopic experiment. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C07.00008: Untethered Shape-changing elastomer via liquid-gas phase transition Maïka Saint-Jean, Benoit Roman, Etienne Reyssat, Jose Bico We present a new system capable of untethered shape-morphing, using an elastomer-alcohol composite capable of large expansion when heated. |
Monday, March 15, 2021 4:36PM - 5:12PM Live |
C07.00009: All-in-One Design of Soft Machines Invited Speaker: Pierre-Thomas Brun In our world filled with human innovation and technology we hardly scratch the surface of what has been formed in nature. In particular, the use of soft structures to accomplish complex tasks is still primarily the handiwork of biology. To bridge the gap on nature, we introduce an all-in-one approach to building soft machines. Using the powerful rules of fluid mechanics and silicone elastomers, fluid-mediated networks can be "frozen'" to provide unique functional materials Instead of relying on the assembly of individual parts, our approach harnesses interfacial flows to robustly produce monolithic pneumatic actuators whose shape can easily be tailored depending on the intended application. While our methodology enables the rapid assembly of classic soft robots, e.g. grippers, and their programming, e.g. sequential motion following a monotonic stimulus, it also paves the way towards new possibilities, e.g. the fabrication of vascular structures. |
Monday, March 15, 2021 5:12PM - 5:24PM Live |
C07.00010: Architected balloons Victor Charpentier, Stephane Bourgeois, Joel Marthelot Balloons and inflatable structures guarantee safe and non-threatening interactions with their surroundings. They are soft and smooth, easy to transport and to deploy but often lack mechanical stability. Yet, they are relevant solutions for human-robot interactions and for the robotic manipulation of fragile goods. Here we study how the addition of local surface artifacts, creating an architected material, can lead to tailor-made deployed geometry for tube like balloons while allowing to retain control over the mechanical behavior during deployment. We first characterize the mechanical behavior of large areas of architected materials (sheet and tubes) using a combination of experiments and numerical nonlinear homogenization methods. Several parametric microstructure geometries are then evaluated and combined to create a flexible geometric platform to adapt the deployed shape to each specific case. Finally, we propose a novel typology of inflatable which architectured material is locally optimized to create global form adequation with the target geometry and required deployed mechanical properties. |
Monday, March 15, 2021 5:24PM - 5:36PM Live |
C07.00011: Shape programming by modulating actuation using zigzag patterns Tian Gao, Emmanuel Siéfert, Antonio DeSimone, Benoit Roman Zigzags structures can be found in a wide variety of fields. For instance, the future leaves of hornbeam are folded in the buds into zigzagging features that deploy as the leaves grow. This natural example has been the source of inspiration to develop origami designs. Here, we present a novel strategy where inextensible thin patches are sealed along zigzag paths to generate complex shape transformation under applied pressure. |
Monday, March 15, 2021 5:36PM - 5:48PM Live |
C07.00012: Discrete 4D printing Kyung Eun Kim, Christian Santangelo 4D printing allows one to fabrication 3D objects from patterned, 2D sheets by locally growing a material. Finding the optimal shape from a pattern of growth is challenging, owing to the fact that there may be many solutions (or none) that can accommodate prescribed growth. Here, we consider a discrete analogue of this problem: how many 3D configurations can accommodate the prescribed growth of the length of edges of a graph and how does that depend on the topology of the graph? In our analysis, propose an optimal discrete structure for which it is computationally easier to find shape given edge lengths and propose a way to count possible solutions. |
Monday, March 15, 2021 5:48PM - 6:00PM On Demand |
C07.00013: Pluripotent Magnetically Actuated Origami Dora Kassabova, Matthew Pinson, Paul L McEuen, Itai Cohen Recently we showed that it is possible to fold a magnetically patterned sheet into a desired target shape. Here, we attempt to embed multiple magnetically actuated folding patterns into a single sheet. Our idea is that if the folding patterns are sufficiently different so that they do not share creases, it is possible to design pluripotent sheets with multiple target shapes. To allow both target structures to be controllably accessed, we pattern the facets with magnetic dipoles. The configuration of these magnets is chosen such that, for two specific applied magnetic fields, the resulting torques correspond as closely as possible to the folding of the two designed patterns. Thus by applying a field in the correct direction, we are able to determine which pattern is chosen. Currently we are working on devices that are centimeters in scale. Because magnetically actuated origami design principles are scale invariant, however, such strategies should easily extend to the microscale. As such, this strategy may represent an important step towards creating magnetically responsive micro- and nanoscale pluripotent origami sheets for use in optical metamaterials, implantable medical devices, and robotic actuation. |
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