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 F09: Elasto-X, Combining Elasticity with Capillarity, Granularity, Adhesion, and OthersFocus
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Sponsoring Units: DSOFT Chair: Andrew Croll, North Dakota State University Room: Room 132 |
Tuesday, March 7, 2023 8:00AM - 8:12AM |
F09.00001: Temperature Dependence of Acoustic Properties of Natural Snail Mucus by Brillouin Spectroscopy Dillon Hanlon Brillouin light scattering spectroscopy was used to probe the acoustic properties of a natural gastropod mucus, which consists primarily of water and glycoproteins, over the range -11 oC ≤ T ≤ 52 oC. Two peaks were observed in the spectra: one at a frequency shift of ~ 8.0 GHz present throughout the full temperature range and assigned to the longitudinal acoustic mode of the liquid component of mucus, and another at a shift of ~ 18.5 GHz observed for temperatures ≤ -2.5 oC assigned to the longitudinal acoustic mode of polycrystalline ice Ih. Discontinuous changes in the temperature dependence of the frequency shift, linewidth, and intensity of these peaks and, consequently, in the hypersound velocity and sound absorption occur at T = -2.5 oC. These changes are accompanied by the appearance in the Brillouin spectrum of a spectral peak due to ice for T ≤ -2.5 oC and together suggest that the mucus undergoes a phase transition from a viscous liquid state to one in which liquid mucus and solid ice phases coexist. The freezing point hysteresis relative to that of water and failure of the liquid-solid transition to proceed to completion is due to inhibition of ice growth caused by glycoprotein adsorption and incorporation. Furthermore, analysis on Brillouin linewidth (FWHM) and consequently the viscosity provide information on the activation energy of the gastropod mucus. The lack of measurable differences in sound absorption for samples containing various amounts of liquid mucus and ice suggests that increased viscosity and the fact that these glycoproteins crosslink to form a polymer network, rather than an increase in the quantity and/or size of ice crystallites in the liquid phase, is the dominant mechanism for increased damping of hypersound with decreasing temperature. |
Tuesday, March 7, 2023 8:12AM - 8:24AM |
F09.00002: The elastic Leidenfrost effect—An interplay between elasticity and vapor pressure. Vicente Luis L Diaz Melian, Scott Waitukaitis, Isaac Lenton, Jack Binysh, Anton Souslov When a liquid droplet comes near a surface significantly above its boiling temperature, vaporization can become sufficient to cause it to levitate—this is the Leidenfrost effect [1]. Vaporizable soft solids, e.g., hydrogels, can also exhibit levitation [2], and additionally a sustained bouncing effect [3]. The interplay of elasticity and vapor pressure is essential for these behaviors, but the nature of this interaction is not fully understood. Previous experiments with lateral-view videography [2,3] were insufficient to observe what happens below levitating hydrogels, unable to resolve levitation heights smaller than 20 micrometers, let alone the surface profile of the underbelly. In this talk, I will present results using a three-laser, high-speed interferometric imaging system that allows us to resolve levitation heights down to ~1 micrometer and measure the full height profile. With our system, we can tease out the system's evolution over timescales ranging from a millisecond to a minute, thus promising to shed light on this unique interplay between elasticity and vapor pressure. |
Tuesday, March 7, 2023 8:24AM - 8:36AM |
F09.00003: Wet-a-materials: designing hairy surfaces for droplet manipulation Mengfei He, Marianna Marquardt, Samay Narasimhamurthy, Gentian Muhaxheri, Hao Jiang, Chris Santangelo, Teng Zhang, Anupam Pandey, Joseph D Paulsen Many insects evolve hairy pads to interact with wet or mucus-covered environments. In turn, the mechano-geometry of the soft substrates determines the fate of liquids attaching to the hairs. Here, we elucidate such complex behaviors by investigating the process of one liquid droplet migrating between two elastic fibers. We show that the splitting proportion of a droplet between two fibers has a simple and sensitive dependence on the hair orientations. We then couple the substrate deformation with such fiber orientations, facilitating a novel functionality of sustained droplet transport among arrays of fibers. Our work points to a new regime of material design: combining elasticity and wetting properties through soft texture arrangements. Our results could be adapted to understanding biological behaviors or aiding designs in pharmaceutical manufacturing. |
Tuesday, March 7, 2023 8:36AM - 9:12AM |
F09.00004: active elastica Invited Speaker: Ousmane Kodio Active or passive, matter that has the form of filaments can be observed at all scales in nature. Examples include DNA, hairs, snakes, eels, plants, beams, solar flares, and galactic filaments. Many studies have been performed when the constituent matter of these structures is made of passive substance, as is the case of beams, cables, strings, etc. However, for modeling living filamentary structures, there are still deficiencies in our understanding due to the lack of a general constitutive theory relating the growth to the stresses. In this talk, we discuss some canonical examples of combining Euler's elastica with activity as a way to gain insights into the growth and form of some living matter. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F09.00005: Multifunctional Hairy Textures Fabricated with Embedded 3D Printing Yun Seong Kim, Wonsik Eom, Sameh H Tawfick Long slender hairs grow and surface and form very soft textures due to their slenderness. We developed a new embedded 3D printing method to print hairs with a high aspect ratio and controlled spacing. Embedded 3D printing is a direct ink writing technique conducted inside a support gel, not in the air. The gel allows the printed fibers to rapidly solidify and stiffen by the solvent exchange method, while remaining supported by the gel to resist gravitational forces during the printing process. With the method, we were able to fabricate hairy surfaces where the fibers are rooted in a PDMS substrate. First, the printability window and parameters will be presented. Then, the multifunctionality of the surface textures will be demonstrated via the elastocapillary effect and the hair bending mechanism will be explained with scaling laws. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F09.00006: Thermodynamic lubrication in the elastic Leidenfrost effect Jack Binysh, Indrajit Chakraborty, Mykyta Chubynsky, Vicente Luis L Diaz Melian, Scott R Waitukaitis, James E Sprittles, Anton Souslov The elastic Leidenfrost effect occurs when a vaporizable soft solid is lowered onto a hot surface. Evaporative flow couples to elastic deformation, giving spontaneous bouncing or steady-state floating. The effect embodies an unexplored interplay between thermodynamics, elasticity, and lubrication: despite being observed, its basic theoretical description remains a challenge. Here, we provide a theory of elastic Leidenfrost floating. As weight increases, a rigid solid sits closer to the hot surface. By contrast, we discover an elasticity-dominated regime where the heavier the solid, the higher it floats. We show that this elastic regime is characterized by Hertzian behavior of the solid's underbelly and derive how the float height scales with materials parameters. Introducing a dimensionless elastic Leidenfrost number, we capture the crossover between rigid and Hertzian behavior. Our results provide theoretical underpinning for recent experiments, and point to the design of novel soft machines. |
Tuesday, March 7, 2023 9:36AM - 9:48AM |
F09.00007: Elastocapillary painting: deposition of fluid trapped within fiber arrays Christopher M Ushay, Pierre-Thomas Brun When a brush is dipped in a fluid, capillary forces etrain the liquid within the dense forests of hairs as individual bristles coalesce. As the brush is subsequently brought against a surface, as in processes such as painting, the bundles of bristles deform as the entrained fluid transfers from the brush onto the substrate. While capillary wicking within elastic porous media has been well-studied, the transfer of fluid from the deformation of an elastocapillary bundle remains relatively unexplored. Here we explore this transfer process using simplified paintbrushes composed of closely-packed arrays of elastic beams. Upon wetting a brush with oil, we study two modes of painting: stamping, in which a brush is pressed vertically onto a plate, and brushing, where it moves parallel to the plate after contact. In both cases, the displacement of the brush against the substrate strongly affects drainage from the elastic medium. In the former case, we find that the speed of retraction can affect the proportion of fluid transferred due to liquid bridge breakup. Meanwhile, in the latter case the initial fluid layer can fully dewet from bristles at rates dependent upon brush geometry and the speed of dragging. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F09.00008: Healable Self-assembled Magneto-elastic Networks with Robust Mechanical Properties Xinyan Yang, Sinan Keten Magneto-active soft materials show significant potential in the applications of soft robotics, control systems, and waveguides due to their programmable shapes, adaptive stiffness, and tunable strength, arising from magnetic-elastic coupling. Magneto-elastic networks coming from this composite design have been fabricated by 3D printing and laser cutting techniques as a monolithic body. These architected network materials offer great energy dissipation capacity per weight under impact but the damage incurred is permanent. To overcome this, a novel magneto-elastic network that can be self-assembled from elastic elements decorated with permanent magnets under random vibrations is proposed in this work. The magneto-elastic unit configuration is shown to dictate the assembled network topology. The design criteria for those units to form mechanically robust networks are derived based on computer simulations, energetic analyses, and experimental validation. Once subjected to large conformational changes or fracturing into pieces in extreme environments, these magneto-elastic lattices can self-heal to their original functional structure by first resetting to the ground state and then reassembling. The self-assembly and self-healing properties enable them to be fabricated and repaired on-the-fly. This work combines concepts from magnetic handshake materials and thermalized granular systems with elastic network designs to understand the self-assembly, elasticity, and failure mechanisms of elastic bar elements with sticky magnetic ends. The presented work will broaden the engineering applications of magneto-elastic soft materials in the field of fatigue-free reusable protective materials and actuators. |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F09.00009: Braiding microscale fibers using capillary forces Ahmed Sherif, Cheng Zeng, Maya Winters Faaborg, Vinothan N Manoharan Braids of microscale fibers have electrical and mechanical properties that make them essential to applications such as high-frequency electronics and textiles. However, industrial braiding machines cannot easily make such ‘microbraids,’ because the forces they exert tend to break the fibers. We show that capillary forces can be used to manipulate the fibers and coax them into braids and weaves. We do this by using capillary machines, 3D-printed devices containing channels that trap floating objects using repulsive capillary forces [1]. I will explain how the topology of the braid or weave is determined by the device geometry and movement pattern, and how the elasticity of the fibers affects the braiding process. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F09.00010: Surface stress drives large material deformation to smooth compliant solids Lebo Molefe, Mojtaba Abdolkhani, John M Kolinski Surface stress is a fundamental property affecting the interfacial mechanics of compliant solid structures. Previous experiments demonstrating how surface stress rounds and flattens sharp features have been largely limited to the two-dimensional (2D) and nearly planar case, studying rectangular ridges of initial height h0 and initial width w0, where h0/w0 is small (h0/w0 << 1). We microfabricate three-dimensional (3D) compliant structures with non-negligible aspect ratio (h0/w0 ~ 1) and observe that micropillar grids made of a compliant polymer in contact with air undergo spacing-dependent deformation, which is largest at low spacings and reaches a constant value at large spacings. This spacing-dependent behavior suggests an elastocapillary interaction between the structures at small spacing, whereas the asymptotic value suggests a limiting distance over which long-range interactions between pillars apply. The existing analytical solution for low aspect ratio structures appears to underpredict deformation for structures with higher aspect ratio, so we employ three-dimensional finite element analysis to model the large deformation. Our numerical results show large rotation within the material, explaining the discrepancy between our data and a low-amplitude theory. Finite element analysis also offers intriguing insights into the problem, such as predicting stress field maps and investigating the competition between bulk and surface energy. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F09.00011: Controlling Droplets with Geometry Samay Hulikal, Christian Santangelo, Mengfei He, Joseph D Paulsen Fluid droplets can both drive and be driven by shape changes in soft materials. The interplay between elasticity and capillarity leads to diverse natural phenomena — from the buckling and closure of airway tubes in lungs to the spooling and packing of spider silk by droplets. We investigate the influence of geometry on the behavior of droplets. We find ways to manipulate drops by changing the geometrical parameters of the underlying soft substrate. Understanding these interactions lets us control tiny amounts of fluid and opens up the possibility of using metamaterials to maneuver liquids and vice versa. |
Tuesday, March 7, 2023 10:36AM - 10:48AM |
F09.00012: Beading is the new jamming: leveraging compliance and rigidity in discrete shape morphing structures Lauren Dreier, Trevor J Jones, Andrej Kosmrlj, Pierre-Thomas Brun From the pragmatic act of covering to the whims of haute couture, civilizations throughout history have employed textiles in some of the most demanding yet ubiquitous engineering scenarios. Assembled by hand or machine, networks of fibers can be manipulated into complex three-dimensional geometries, exhibiting emergent mechanical properties such as anisotropic stretch and abrasion resistance while remaining compliant. As such, fabrics cannot typically withstand compressive forces, limiting their applicability in some settings. Here we show that by introducing discrete rigid units in textiles, i.e. beads, we can form shape-morphing objects with tunable stiffness and the capacity to withstand large compressive forces. Drawing inspiration from traditional beadwork, we devise a model experiment that is initially flat but morphs into a shell when tension is applied. We investigate and rationalize its mechanical properties. Our findings could have implications ranging from soft robotics to architecture, where the potential utility of shape morphing is often limited by length scale due to gravity and external loads. |
Tuesday, March 7, 2023 10:48AM - 11:00AM |
F09.00013: Kuttsukugami Andrew B Croll, Timothy J Twohig, Michael D Bartlett, Ravi Tutika In recent years, origami design has been used by the engineering community to solve many problems and has inspired much fundamental study of its mechanisms, limits, and geometry. While not often discussed, origami design suffers from several limitations. For example, origami systems are not easily reconfigurable (as creases or hinges require memory in the sheet) and cannot easily create curved or closed structures. In this work, we show how sticky sheets (kuttsukugami) can not only create identical structures as in traditional fold-based origami but can also be used to resolve many of the limitations. We show how sticky sheets can easily create stable, curved structures, how they constitute a truly reusable and reconfigurable system, how they allow the use of materials that cannot be used in traditional origami and how their principles can be used to create measurement, encapsulation schemes and soft robotic elements. |
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