Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P14: Mechanical Metamaterials II |
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Sponsoring Units: GSNP GSOFT Chair: Katia Bertoli, Harvard University Room: 273 |
Wednesday, March 15, 2017 2:30PM - 2:42PM |
P14.00001: Bending-induced folding,~an actuation mechanism for plant reconfiguration. Denis Terwagne, Jérémy Segers Inspired by the sophisticated mechanism of the opening and closing of the ice seed plant valves (Aizoaceae), we present a simple model experiment of this mechanism based on an origami folding. By imposing a curvature to one of the plate connected to a fold designed along a curved path, we actuate its opening and closing. The imposed curvature induces inner mechanical constraints that give us a precise control of the deflection angle, which ultimately leads the fold to close completely. In this talk, we will present an analysis and characterization of this mechanism as a function of the geometrical and mechanical parameters of the system. From these insights, we will show how to build origami pliers with tunable mechanical properties. Possible out comings that might arise in various fields, ranging from deployable engineered structure to soft robotics and medical devices, are discussed. [Preview Abstract] |
Wednesday, March 15, 2017 2:42PM - 2:54PM |
P14.00002: Origami structures for tunable thermal expansion Elisa Boatti, Katia Bertoldi Materials with engineered thermal expansion, capable of achieving targeted and extreme area/volume changes in response to variations in temperature, are important for a number of aerospace, optical, energy, and microelectronic applications. While most of the proposed structures with tunable coefficient of thermal expansion consist of bi-material 2D or 3D lattices, here we propose a periodic metastructure based on a bilayer Miura-Ori origami fold. We combine experiments and simulations to demonstrate that by tuning the geometrical and mechanical parameters an extremely broad range of thermal expansion coefficients can be obtained, spanning both negative and positive values. Additionally, the thermal properties along different directions can be adjusted independently. Differently from all previously reported systems, the proposed structure is non-porous. [Preview Abstract] |
Wednesday, March 15, 2017 2:54PM - 3:06PM |
P14.00003: Kirigami-based PVDF thin-film as stretchable strain sensor Nan Hu, Dajing Chen, Nanjing Hao, Shicheng Huang, Xiaojiao Yu, John X.J. Zhang, Zi Chen Kirigami, as the sister of the origami, involves cutting of 2D sheets to form complex 3D geometries with out-of-plane patterns. Motivated by the development of the high-stretchable biomedical devices, we explore the stretchability of the kirigami-based PVDF thin film under tension. Our structural prototypes include a set of 2D geometry with kirigami-based pattern cutting on PVDF thin films. We first used paper models to generate a wide range of cutting patterns to study the deformation under compression tests, the results of which are compared with finite element simulations. We then proceeded to test different kirigami-based designs to identify geometric parameters that can tune the post-buckling response and strain distribution. Next, we fabricated and tested the PVDF thin film with kirigami pattern. Experiments showed that the PVDF film in the absence of cutting can be stretched to a limited extent and will break upon further stretching. In contrast, the kirigami-based films can be stretched up to 100{\%} without failure. Our designs demonstrate the ability to significantly improve the strain range of the structure and sensing ability of a sensor. We envision a promising future to use this class of structural elements to develop highly stretchable materials, structures, and devices. [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P14.00004: Folding of Metamaterials: the Role of Pathways Martin Van Hecke, Alberico Sabbadini, Corentin Coulais We show how hierarchically shaped elastic materials fold and buckle in a sequence of steps when submitted to compression. We highlight how the materials design controls the critical strain of each folding step, and leverage this to manipulate the folding pathway. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P14.00005: Morphological transformations triggered by temperature changes Damiano Pasini, Lu Liu Biological materials can often adapt their micromorphology to efficiently respond to and accommodate temperature changes dictated by the environment in which they live. In this work, we follow this strategy and introduce a class of compliant metamaterials that are programmed to exhibit morphological transformations in response to a set of temperature variations. Shape transformation mechanisms are designed in each building block by finite element simulations, and used to fabricate proof-of-concept metamaterials that are responsive to temperature fluctuations. A soft elastomer is casted into a rigid periodic frame that can reproduce scaling, axial or shear deformation. The result is a metamaterial that can accomplish macroscopic shape transformations that are reversible and governed by the level of temperature of the surrounding environment. [Preview Abstract] |
Wednesday, March 15, 2017 3:30PM - 3:42PM |
P14.00006: Evolutionary Design of Flexible and Bistable 2D Mechanical Metamaterials. Nitin Singh, Martin van Hecke The physics of many two-dimensional metamaterials can be understood through simple one degree of freedom mechanisms of rotating polygons. Most well known are 'holey sheets' that can be mapped onto mechanism of identical rotating squares or rectangles. Here we use evolutionary algorithms to design aperiodic, yet~flexible or bi(multi)-stable metamaterials. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 3:54PM |
P14.00007: Buckling-induced kirigami Ahmad Rafsanjani, Katia Bertoldi We investigate the mechanical response of thin sheets perforated with a square array of mutually orthogonal cuts, which leaves a network of squares connected by small ligaments. Our combined analytical, experimental and numerical results indicate that under uniaxial tension the ligaments buckle out-of-plane, inducing the formation of 3D patterns whose morphology is controlled by the load direction. We also find that by largely stretching the buckled perforated sheets, plastic strains develop in the ligaments. This gives rise to the formation of kirigami sheets comprising periodic distribution of cuts and permanent folds. As such, the proposed buckling-induced pop-up strategy points to a simple route for manufacturing complex morphable structures out of flat perforated sheets. [Preview Abstract] |
Wednesday, March 15, 2017 3:54PM - 4:06PM |
P14.00008: Nanoscale Sheets for Rapid Bidirectional and Sequential Folding Baris Bircan, Marc Miskin, Kyle Dorsey, Itai Cohen, Paul McEuen Using readily available planar fabrication methods, we are developing self-folding devices that consist of patterned quasi-two dimensional sheets. These devices, formed by stacking nanometer thick layers of different materials, controllably bend as a result of differential stress. This stress is generated by ion substitution reactions, which occur on a time scale of about a second in nanoscale sheets. By patterning the sheets laterally, we localize the bending and generate folds with micron scale radii of curvature in the direction of our choice. Finally, we show that this approach offers a wide range of mechanical, chemical, electrical, magnetic and biological functions as well as a path to sequential folding through the individual programming of layers. [Preview Abstract] |
Wednesday, March 15, 2017 4:06PM - 4:18PM |
P14.00009: Marginal elasticity of periodic triangulated origami Bryan Chen, Dan Sussman, Tom Lubensky, Chris Santangelo Origami, the classical art of folding paper, has inspired much recent work on assembling complex 3D structures from planar sheets. Origami, and more generally hinged structures with rigid panels, where all faces are triangles have special properties due to having a bulk balance of mechanical degrees of freedom and constraints. We study two families of periodic triangulated origami structures, one based on the Miura ori and one based on a kagome-like pattern due to Ron Resch. We point out the consequences of the balance of degrees of freedom and constraints for these "metamaterial plates" and show how the elasticity can be tuned by changing the unit cell geometry. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P14.00010: Circular kirigami structures: from bowl to vase shapes Jose Bico, Etienne Lepoivre, Hadrien Bense, Etienne Reyssat, Benoit Roman Thin sheets have the property to be more difficult to stretch than to bend. This common fact constitutes a strong limitation to the development of stretchable electronics devices since thin brittle electrical circuits are prone to rupture under modest strains. Parallel alternate cuts on a thin plate can transform an actual bending deformation into a significant apparent elongation. Such “kirigami” structures provide a simple a solution to stretch a thin plate without damage and have been proposed for many applications ranging from graphene-based devices to adjustable diffraction gratings or tunable solar panels. Most studies have focused on 1D systems. We are interested in the deformation of structures obtained by applying arced cuts on a disk. Upon stretching, the initially flat plate is transformed into an axisymmetric 3D shape. Depending on the initial cut, bowl, cone, trumpet or even complex vase shapes are obtained. [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P14.00011: Controlling large deformations of marginal disordered structures Menachem Stern, Matthew Pinson, Alexandra Carruthers, Elizabeth Chen, Arvind Murugan Metamaterials are typically sought to demonstrate specific responses in the non-linear deformation regime. However, analytic methods for these systems are often based on linear approximations. We find that practical questions of actuation in origami have counter-intuitive answers due to a strong mismatch between linear and non-linear theory near the special flat state, where all modes meet. Linear-non-linear mismatch generically leads to an exponential number of `dead end' folding modes, resulting in an emergent glassy energy landscape around the flat state. This landscape makes refolding of a pre-folded creased sheet much more difficult than one would expect. Conversely, borrowing results from associative memory in neuroscience, we show that structures with multiple programmed folding motions can be much easier to control than expected, as long as the flat state is avoided. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P14.00012: Topological Edge Modes in Active Mikado Networks Di Zhou, Leyou Zhang, Xiaoming Mao Mechanical properties of disordered fiber networks are not only important in understanding a broad range of natural (such as the cytoskeleton and the extracellular matrix) and manmade materials (such as aerogels and porous media) but also exhibit interesting and rich physics. In this talk, we discuss how topological floppy edge modes can emerge from these fiber networks as a result of active driving. It is known that straight fibers in a network carries a state of self-stress and bears a bulk floppy mode. We find that, interestingly, by driving the network with a tiny perturbation, the bulk modes evolve into edge modes. We introduce a new transfer matrix formulation that can be applied to this strongly disordered system, to characterize the topological edge modes. We also discuss possible implications of these edge modes in biological processes. [Preview Abstract] |
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P14.00013: Encoding mechano-memories in filamentous-actin networks Sayantan Majumdar, Louis Foucard, Alex Levine, Margaret L. Gardel History-dependent adaptation is a central feature of learning and memory. Incorporating such features into `adaptable materials' that can modify their mechanical properties in response to external cues, remains an outstanding challenge in materials science. Here, we study a novel mechanism of mechano-memory in cross-linked F-actin networks, the essential determinants of the mechanical behavior of eukaryotic cells. We find that the non-linear mechanical response of such networks can be reversibly programmed through induction of mechano-memories. In particular, the direction, magnitude, and duration of previously applied shear stresses can be encoded into the network architecture. The `memory' of the forcing history is long-lived, but it can be erased by force applied in the opposite direction. These results demonstrate that F-actin networks can encode analog read-write mechano-memories which can be used for adaptation to mechanical stimuli. We further show that the mechano-memory arises from changes in the nematic order of the constituent filaments. Our results suggest a new mechanism of mechanical sensing in eukaryotic cells and provide a strategy for designing a novel class of materials. [Preview Abstract] |
Wednesday, March 15, 2017 5:06PM - 5:18PM |
P14.00014: Controlling bond-bending forces in disordered meta-material networks Nidhi Pashine, Daniel Reid, Jason W. Rocks, Andrea J. Liu, Juan de Pablo, Sidney R. Nagel Disordered elastic networks can be tuned to have unconventional response by pruning bonds selectively. This has been demonstrated in simulations of networks consisting of harmonic, central-force springs between nodes. We have experimentally built such networks by laser cutting them out of rubber sheets. The bond-bending forces inherent in these realizations significantly and adversely impact the network response and in some cases destroy its ability to exhibit the desired behavior. We can control the strength of bond-bending forces by suitably designing the geometry and aspect ratio of the struts. We can also include bond-bending forces directly into the tuning algorithm. Both strategies allow us to create a desired response in our experimental networks. [Preview Abstract] |
Wednesday, March 15, 2017 5:18PM - 5:30PM |
P14.00015: Buckling, Jamming, and Structure Formation in Elastogranular Systems Douglas Holmes, David Schunter, Ahmad Mojdehi, Sophia Perriseau, Regina Czech, David Dillard The coupling of slender rods and disordered granular matter occurs during the growth of plant roots, the bending and buckling of oil pipelines and drill strings, and the creation of subterranean infrastructure with microtunneling and trenchless techonology. These highly nonlinear interactions also present a means to develop jammable, amorphous metamaterials that are disordered on the scale of their local constituent units, yet result in remarkably strong macroscale ordered structures. Elastogranular jamming consists of the disordered coupling of granular media and slender structures to generate structural integrity. In this talk, we will quantify the buckling of a partially inserted elastica into a bed of granular media, and describe structure formation in planar elastogranular systems within a 2D array of beads. Elastica confinement and granular disorder-to-order transitions lead to the emergence of periodically folded structures with a characteristic length scale dictated by the packing fraction of the granular media. We examine the role of local granular order on the resulting elastica confinement, and granular reconfiguration. The resulting 2D elastogranular arrays provide a framework for amorphous mechanical metamaterials that enable pourable, jammed structures. [Preview Abstract] |
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