Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y21: Textiles and Topology: Physics of Knots and TanglesFocus Recordings Available
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Sponsoring Units: DSOFT DPOLY GSNP Chair: Michael Dimitriyev, University of Massachusetts Room: McCormick Place W-185D |
Friday, March 18, 2022 8:00AM - 8:12AM |
Y21.00001: Developing a Constitutive Model for Knitted Fabrics Sarah E Gonzalez, Michael S Dimitriyev, Krishma Singal, Elisabetta A Matsumoto Knitting is the manipulation of a one-dimensional yarn into a two-dimensional lattice of interconnected loops and a craft that has been done for centuries in both manual and mechanized settings. In comparison to weaving, knitted fabrics have more elastic properties and as such are typically used for cuffs, hats, and socks. Knitted fabrics have two basic stitches: a new loop is pulled through an existing loop from the front (purl) or the back (knit). Previous simulations show how knitted fabric behaves differently for different fabric types, indicating that fabric behavior has a large dependence on the topology of the stitches themselves. Beyond fabric types, the yarn itself has several mechanical properties that can be experimentally measured, such as the bending modulus, compression modulus, and length of yarn per stitch. By exploring the parameter space of yarn properties for a single fabric type, we can further determine how yarn elasticity and manufacturing processes individually affect fabric behavior. These studies also allow us to identify the properties that have the largest effects on the mechanics and develop a constitutive model to link yarn and fabric elasticity. |
Friday, March 18, 2022 8:12AM - 8:24AM |
Y21.00002: Topological mechanics of living worm blobs Vishal P Patil, Harry Tuazon, Tuhin Chakrabortty, Jorn Dunkel, Saad Bhamla Tangled filamentary objects are ubiquitous in biological and physical systems, from chromosomal DNA to turbulent vortex lines. Despite important recent progress, the interplay of topology, activity and elasticity in the context of many-body tangle interactions is not well understood. Here, we model California blackworms (Lumbriculus variegatus), which are known to slowly form tangles or blobs over minutes with their flexible bodies but untangle in milliseconds under stress. In this talk, we will develop a topological framework to understand the slow formation and fast separation of active tangles, combining elastic fiber simulations with a low-dimensional tangle representation. Using this model, we will describe the topological moves that guide tangle self-assembly and demonstrate that helical waves of alternating chirality, a characteristic dynamical feature of stressed, untangling worms, represent a possible unweaving mechanism that simplifies tangle topology. Our results illustrate the design principles underlying a self-assembling and disassembling tangle, and pave the way for exploring topologically tunable active matter. |
Friday, March 18, 2022 8:24AM - 9:00AM |
Y21.00003: Kinetoplast Invited Speaker: Alexander R Klotz DNA: topology of molecular chainmail Abstract: DNA topology is usually categorized into linear and circular molecules, with the latter having varying degrees of supercoiling. A much more complex DNA topology is found in the mitochondria of trypanosome parasites, which cause diseases such as Sleeping Sickness and Leishmaniasis. Their mitochondrial DNA consists of thousands of topologically connected loops, forming a two-dimensional but spatially curved network known as a kinetoplast, which can be thought of as "molecular chainmail." Much like linear DNA has served has a model polymer for several decades, kinetoplasts provide the opportunity to study the physics of exotic types of materials, including two dimensional materials and "Olympic gels," which are held together by topological rather than covalent bonds. In this talk, I will summarize what is known about the biology and topology of kinetoplast networks and overview recent work exploring the polymer physics of kinetoplasts in solution. Finally, I will highlight recent experiments attempting to measure the percolation threshold of kinetoplast networks through destructive testing and recent discoveries based on fluorescence microscopy. |
Friday, March 18, 2022 9:00AM - 9:12AM |
Y21.00004: Laddering propagation in Weft Knit Fabrics Helen E Read, Kausalya Mahadevan, Katia Bertoldi We use weft knit fabrics every day, as their stretchiness makes them ideal for clothes that are easy to put on and can conform to our bodies. However, their highly interconnected structures means that a single yarn breaking can lead to large visible holes which are caused by unsupported loops that propagate vertically and create a laddering effect. Here, we use experiments and simulations to investigate this phenomenon. We study various knit architectures and identify loading conditions that result in this catastrophic event. Additionally, we harness horizontal transfers and tuck stitches to design knits that ladder only along diagonal lines of our choosing. Finally, we incorporate randomness into the design to realize an ideal density of stable holes--known as yarnovers in hand knitting-- capable of localizing failure. Together, we expect this framework to enable the design of knit architectures that retain many of the desirable properties of weft knits, while being more resistant to laddering propagation. |
Friday, March 18, 2022 9:12AM - 9:24AM |
Y21.00005: Statistical Knitting and the Resulting Macroscopic Emergent Behavior Krishma Singal, Michael S Dimitriyev, Elisabetta A Matsumoto Knitted fabrics are programmable materials whose elastic properties stem from the spatial arrangement of stitches. The most common fabrics are simple periodic patterns of the two most elementary stitches, the knit stitch and the purl stitch. Our previous studies have shown that one can introduce soft deformation modes to a pattern by alternating between knit and purl stitches. This motivates the question: how does alternating between these stitches on different lengthscales control macroscopic elastic behavior of the fabric? We systematically study the mechanics of disordered, uncorrelated arrangements of knits and purls and gradually introduce correlations. To do this we model a collection of knits and purls as a binary mixture undergoing phase separation. Following Cahn-Hilliard dynamics, we track the development of knits and purls into domains and manufacture the resulting pattern at different stages of coarsening. We expect that the macroscopic mechanical behavior of each generated fabric will depend on the collective response of correlated structures over a variety of lengthscales, and we wish to understand the role of soft elasticity on macroscopic emergent behavior. This statistical mechanics-motivated study is an unexplored design space for fabrics. |
Friday, March 18, 2022 9:24AM - 9:36AM |
Y21.00006: The mechanical response of periodic and aperiodic multistable knit architectures. Kausalya Mahadevan, Vanessa Sanchez, Katia Bertoldi Weft, or v-bed, knitting is a versatile process used to manufacture a huge range of objects including clothing, vehicle upholstery, ducting, and aerospace parts. The stitches formed on either bed are identical reflections of each other. We harness this existing symmetry in a knit stitch and a periodic pattern to manipulate the natural curvature of the material into a self-folding pattern which exhibits multiple stable configurations. We explore the energy landscape of these knits using finite element simulations, and tune the geometric parameters to optimize their mechanical properties. We also investigate the mechanical effects of non-periodicity on these structures. This ranges from a single unit cell with a defect to a completely random textile, which does not exhibit the same large scale folding. |
Friday, March 18, 2022 9:36AM - 9:48AM Withdrawn |
Y21.00007: Inverse Design of Mechanical Responses in Programmable Knitted Fabrics Xiaoxiao Ding, Christopher H Rycroft Knitted fabrics that are engineered to be compliant and multi-functional have been applied in many applications, such as wearable devices, e-textiles and soft robotics. In order to optimize the behavior of knitted fabrics, we develop a yarn-level mechanical simulation framework to study the structure--response relationship on the representative unit of all basic knitted structures. We use this framework to explore the design space of knitted fabrics that can be programmed with multiple representative unit structures and with varying mechanical material properties, such as elastic stiffness and bending stiffness. Our framework allows us to perform inverse design efficiently and robustly. |
Friday, March 18, 2022 9:48AM - 10:00AM |
Y21.00008: Nonwoven textile structures – Commodity pathways to auxeticity Prateek Verma, Anselm C Griffin, Meisha L Shofner Auxetic materials and structures possess a negative Poisson's ratio, which is inconsistent with intuition regarding a structure's response to deformation. Specifically, auxetic structures expand in tension and contract under compression, leading to sought after damping properties, impact resistance, and opportunities for constructing deployable structures. While this behavior may be achieved through intricate structural design, more common materials and structures can display this mechanical response, leading to a class of commodity auxetics. Our research has examined nonwoven fabrics and paper from this viewpoint and found that an out-of-plane auxetic response can be readily realized in fiber networks. By examining a variety of nonwoven structures, we have observed different mechanisms for the auxetic response and been able to affect the magnitude of the auxetic response by incorporating post-processing strategies. Overall, these results provide some of the needed general processing-structure-property relationships for producing auxetic fabrics as well as demonstrate pathways to producing these structures through conventional, large-scale methods. |
Friday, March 18, 2022 10:00AM - 10:12AM |
Y21.00009: Mechanics of wet fibrous bundles Camille Duprat, Janine Nunes, Zehao Pan, Howard A Stone There are several ways of forming macroscale elastic structures from a fibre suspension: paper sheets are obtained from the dewatering of a cellulosic fibre suspension on a forming grid, and it has been shown recently that soft viscoelastic gels are formed upon extrusion of a microfibre suspension. |
Friday, March 18, 2022 10:12AM - 10:24AM |
Y21.00010: Fracture and tensile strength of aggregates of frictional flexible fibers Ignacio Andrade-Silva, Olivier Pouliquen, Joel Marthelot Flexible frictional fibers aggregates show significant cohesive behavior without the need of glue between particles. In nature, this effective cohesion provides mechanical stability of natural structures such as birds’ nests or beaver dams. Here, we aim to rationalize the cohesive strength of a disordered assembly of flexible frictional fibers. We design a non-destructive experimental protocol that allows us to access the tensile strength of the aggregate through force-displacement measurements. The results show that the tensile strength is highly dependent on the initial packing fraction set by the pre-compression. X-ray microtomography gives us access to relevant quantities such as the number of contacts, average fibers curvature, and fiber reorientation throughout the tensile process. We construct a simple mechanical model taking into account the number of fibers participating in the fracture process that well captures the effective cohesion of the assembly. |
Friday, March 18, 2022 10:24AM - 10:36AM |
Y21.00011: A soft gripper with embedded soft sensors for extremely flexible objects Uhsang Ahn, Changho Yun, Subyeong Ku, Yong-Lae Park, Ho-Young Kim Despite continued developments in robotics and automation technology, the garments industry has maintained a largely labor intensive manufacturing process as the handling of extremely flexible objects, such as textiles, remains challenging. Prior textile grippers have used interlocking needles, suction and electroadhesion; however, tradeoffs between textile damage, textile compatibility and actuation times have hindered widespread industrial adoption. Here we present a pneumatically actuated soft gripper that overcomes the aforementioned drawbacks through utilizing the buckling of an elastic membrane to effectively handle flexible sheets such as textiles. The gripper shows excellent single sheet separation for a wide variety of textiles, even after undergoing in excess of 40,000 cycles, and by embedding soft capacitive sensors, we are also able to deduce the success or failure of grasping and electrical properties. The gripper is also able to grip delicate sheets without causing mechanical folds or creases, suggesting promise in the field of biology and medicine. Theoretical models for the gripping and sensing mechanisms are suggested to further optimize the gripper for widespread adoption. |
Friday, March 18, 2022 10:36AM - 10:48AM Withdrawn |
Y21.00012: On the topological linkage of finite, entangled, spatial graphs in three-dimensions. Felix Kramer, Carl D Modes The observation, design and analysis of mesh-like networks in crystal chemistry, polymer physics and biological systems has brought forward an extensive catalog of fascinating structures of which a subgroup share a particular, yet critically under appreciated attribute: Intertwinedness. |
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