Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K20: Emergent Mechanics of Active, Robotic, and Living Materials IIIRecordings Available
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Sponsoring Units: DSOFT GSNP Chair: Anton Souslov, University of Bath Room: McCormick Place W-185BC |
Tuesday, March 15, 2022 3:00PM - 3:12PM |
K20.00001: Rapid control of multimodal mechanical metamaterial collapse using pneumatic pressurization Ryan Harne, Lance P Hyatt Pneumatically pressurized mechanical metamaterials have been shown to achieve large deformation and programmable mechanical properties using networks of enclosed cavities. Yet, many applications of pneumatic pressurization are limited by a moderate rate of actuation. Here, a bimodal, dual-stage mechanical metamaterial is presented that achieves rapid switching between collapse modes using pneumatic pressurization and elastic instabilities. The two collapse modes are described using kinematic models where deformation occurs only as ligament bending. Each mode experiences two stages of collapse resulting in fully compact configurations. The collapse modes can be programmed passively with the relative sizes of ligaments and actively through pneumatic pressure to selected cavities. The mechanical properties of a multimodal metamaterial sample under biaxial compression are shown with a gradation of applied pressures. By applying or removing pressure during collapse, the metamaterial will rapidly switch from one collapse mode to the other. This demonstrates an integrated ability to tune the mechanical properties of the metamaterial in real-time. |
Tuesday, March 15, 2022 3:12PM - 3:24PM |
K20.00002: Using Light Sheet Fluorescence Microscopy to measure force generated by contractile actomyosin gels James H Clarke Fluorescence microscopy has been a decades long workhorse for exploring fundamental questions about life. Within the field of soft matter, this modality can facilitate our exploration of life via reconstituted systems. With inspiration drawn from the OpenSPIM open-science platform we report on the design and construction of a multimodal light sheet fluorescence microscope capable of probing the dynamical nature of soft matter systems. Measuring forces in microscopy is a challenge due to the lack of innate contrast mechanisms that describe forces. We demonstrate the ability of this tool to measure total force in actomyosin gels by utilizing a method of mapping 3 dimensional displacements of fluorescent markers due to contractile forces generated by the gel. |
Tuesday, March 15, 2022 3:24PM - 3:36PM |
K20.00003: Using Sub-Riemannian Geometry to Characterize Mechanics of Deformable Systems Brian Day, Elisabetta A Matsumoto, Steve Trettel The motion for most dynamical systems is characterized by external degrees of freedom, such as position and velocity. However, deformable systems have an expanded configuration space that includes internal degrees of freedom. The addition of internal parameters to the systems allows for the possibility of motion without the need for external forces. To produce these deformation mechanics, there needs to be some symmetry breaking present in the environment containing the system, such as through curvature or gauge freedom. The set of motions accessible to the system through pure deformation can be analyzed through sub-riemannian geometry to map how cyclic changes in the internal parameters of the system can translate to net motion of the system. Through considering the mathematical connection between the internal and external degrees of freedom, one can determine what motion is generated by a given deformation of the system. More interestingly, the process can be reserved so as to find the best deformation path to produce a given motion. |
Tuesday, March 15, 2022 3:36PM - 3:48PM |
K20.00004: Extracting Active Fluctuating forces from Fluctuating motions of an active Brownian particle in a quadratic confinement Simin Xia, Chong Shen, Zhiyu Jiang, H Daniel Ou-Yang Fluctuating motions of active Brownian particles are produced by a combination of active and passive forces. Active forces carry the origin and the mechanisms of how the forces are generated. Extracting the active forces from the fluctuating motions of an active particle is nontrivial because the motions produced by the two different forces cannot be distinguished. However, if the particle is confined in a quadratic potential, we found the histogram of the fluctuating positions of the particle is a convolution of the histograms of the active and the passive positions. We hypothesize that if the histogram of the total fluctuating position and the histogram of the Brownian fluctuations are both known, one can extract the histogram of the pure active fluctuation by deconvolution. Because the convolution hypothesis is based on that the force on a particle is a vector sum of the passive and active forces, the validity of the deconvolution procedures will depend on whether they are time scale invariant – typical experimental sampling rates of the particle position are often much longer than that of the molecular fluctuations. Electrophoresis-driven Janus particles in an optical trap and Langevin equation-based numerical simulations were conducted to examine the hypothesis and the effects of sampling time to the deconvolution method. Both the experiments and the Langevin simulation show the deconvolution procedures work well and they are indeed time scale invariant. In conclusion, we extracted active forces from the histogram of the fluctuating position of an active particle in quadratic confinement by deconvolution. |
Tuesday, March 15, 2022 3:48PM - 4:00PM |
K20.00005: Tidal effects on active matter induced by elastic membrane Hussain N Gynai, Shengkai Li, Gongjie Li, Daniel I Goldman In active matter systems, agents can interact not only via contact, but also via fields (like in movement on water or elastic surfaces). To explore active matter dynamics in the presence of time varying fields, we previously studied a 200-gram wheeled vehicle driving on a deformable spandex membrane (d=2.4m) with a static central depression (Li et al., 2019). Our system exhibits rich dynamics, including precessing orbits of a single rigid body. Motivated by internal planetary tidal disruption due to a strong gravitational force, here we develop a mechanism to connect two vehicles via a spring to emulate tidal forces on a nonrigid body. Experiments and simulations reveal three types of trajectories as we vary relative car speeds. One is a tidally locked trajectory where the same vehicle remains closest to the central depression and occurs when the outer car is slightly faster than the inner. The other two types are self-rotations where the vehicles rotate around one another while both revolve around the center, one with retrograde and one with prograde spin. In the tidally locked regime, oscillating the central depression vertically at a frequency comparable to the orbital period produces resonant pumping such that the coupled vehicles increase relative displacement over time. |
Tuesday, March 15, 2022 4:00PM - 4:12PM |
K20.00006: Deformation and collision over a chain of active stochastic particles Mario Sandoval In this work, the response (deformation) of a chain of N-1 active stochastic particles, interacting by nonlinear springs, to an external force is numerically studied and rationalized with a minimal model. It is found that a chain of active stochastic particles linearly interacting presents the classical Hookean deformation with respect to an external force, and that this deformation is independent of the activity in the system. However, when the chain of active particles interacts by means of nonlinear springs (specifically a hard symmetric potential), the chain's average deformation decreases with respect to a passive system under the same conditions. The latter result may shed light on new ways to creating an active metamaterial. |
Tuesday, March 15, 2022 4:12PM - 4:24PM |
K20.00007: Dynamics of self-propelled particles in the vibrated dense granular media Kyungmin Son, Yongjoo Baek, Ho-Young Kim Living organisms and self-propelled particles self-organize into swarms and macrostructure. Reprogramming the self-organization of components provides huge opportunities to modulate structural properties and emergent functions. While structural stability requires the units to assume a solid-like state, the ability to switch target functions requires a certain degree of structural fluidity so that the units can redistribute themselves. Here, we investigate the dynamics of a small number of self-propelled particles placed among a crowd of randomly vibrated granular particles close to the jamming condition in a two-dimensional confinement. By tuning the shape and the polarity of the self-propelled particles, we can control their mobility and pathway inside the densely packed particle crowd. Our experiments and theoretical analysis show that the aspect ratio and the number of self-propelled particles determine the dynamics of the particles along the boundary. These results suggest that merely changing the particle shape and number can effectively modulate the collective motion of a self-organized structure. |
Tuesday, March 15, 2022 4:24PM - 4:36PM |
K20.00008: Unexpected wave-like statistics of coupled walking drops Matthieu Labousse, Konstantinos Papatryfonos, Mélanie Ruelle, Corentin Bourdiol, André Nachbin, John W Bush Walking drops are one of the rare examples of non-quantum wave-particle duality. A series of striking experiments of one walking drop has lead to behaviors that were thought to the peculiar to the quantum scale. The behavior of many particles is now a burgeoning topic in the field. In this talk I will present a recent investigation involving the coupling two walking drops. To our great surprise, we have found that the statistical behaviors of this system shares some non-expected features of collective emission of photons in quantum optics. This result is very intriguing as the quantum counterpart is the signature of non-separable states which in our case, is the result of a collective wave self-organisation. I will discuss potential analogy with the two systems and present our main results. |
Tuesday, March 15, 2022 4:36PM - 4:48PM |
K20.00009: Scale invariance in the dynamics of a non-magnetic ellipsoidal particle lying on a granular thermal bath fluidized Cecilio Tapia-Ignacio, Fernando Donado, Jonathan Azarael Ortiz García, Aldo Arturo Sánchez Granados We studied the Brownian motion of a non-magnetic ellipsoidal particle lying on a granular thermal bath fluidized using a combination of an alternating magnetic field and a constant magnetic field. Using Fourier analysis (FA), we recently found scale invariance in the particle position time series at different effective temperatures. In contrast, particles in the granular bath do not present scale invariance when the effective temperature lowers. In the present contribution, we extended the study to consider two different sizes of the ellipsoidal particle and different values of the constant magnetic field for the thermal bath. In all cases, the Fourier power spectra reveal scale invariance. The time series of the ellipsoidal particle positions in x-direction and the angular time series constructed from rotational motions follow a power law, P(f) ∝ 1/ fβ with β≈2, indicating Brownian-like motion. In the absence of a constant magnetic field, the scale invariance property is valid only for high values of the oscillating magnetic field. In this way, using time series analysis techniques, the characterization of Brownian paths' emergence in this active matter model is achieved. |
Tuesday, March 15, 2022 4:48PM - 5:00PM |
K20.00010: Generalized stochastic engines operating in a single spatially homogeneous yet time-dependent bath Vincent Du, Zhongmin Zhang, Zhiyue Lu In stochastic thermodynamics, molecular machines or motors can operate by harnessing energy from the spatial gradients of either temperature or chemical potential (e.g., nano-Carnot's engines with two thermal baths, or F1-ATPases with two chemical baths of protons). However, it can be energetically costly to create or maintain a sufficient spatial gradient at the length scale of molecules. We argue that enzymes immersed in a temporally changing environment could operate in a brand new regime -- harnessing energy from a single spatially homogeneous bath that varies in time. We provide a minimal solvable model of an enzyme coupled to a bath with time-varying temperature. The periodic variation of the bath then leads to nonzero cyclic currents in the enzyme's state space, which can be used to perform mechanical work or chemical work (i.e., invert the direction of a spontaneous chemical reaction). Analytic solutions to our model can be obtained in the rapid-driving limit. Our model reveals that the wide variety of enzymes existing in living organisms could potentially harness nonequilibrium energy from time-varying environments to perform useful functions. |
Tuesday, March 15, 2022 5:00PM - 5:12PM |
K20.00011: Onset of order in the Vicsek-Kuramoto model with generalized noise Kristian Stølevik Olsen, Luiza Angheluta, Eirik G Flekkoy Complex systems where the constituents are subject to alignment interactions can be found across the scales in Nature, ranging from small biological systems to social behavior on larger scales. Such systems are inevitably also subject to various sources of noise, originating either from external perturbations or internal mechanisms. In active matter systems where alignment leads to swarming behavior the noise typically represent some degree of imperfection in the alignment rule. However, it may also be beneficial to model more complex behavioral patterns as stochastic terms in the equations of motion, like sudden changes in the direction of motion which is not captured by standard Gaussian white noise. By studying a system of self-propelled particles aligning through a Kuramoto interaction, we show that for a large class of noise types the onset of order takes place at a critical interaction timescale that is related to the persistence time of the active system in the non-interacting limit. We consider a special case of Poissonian noise representing abrupt directional changes and study the resulting collective behavior in the partially ordered state right after the transition point. |
Tuesday, March 15, 2022 5:12PM - 5:24PM |
K20.00012: Colloidal hydrodynamics of the bacterial nucleoid and its impact on diffusion and spatial organization in the cytoplasm Alp M Sunol, Brian K Ryu, Jennifer L Hofmann, Roseanna N Zia Computational modeling of the intracellular milieu as a suspension of colloidal macromolecules provides a complementary framework for studying biological cells by providing access to an expanded range of length- and timescales. Colloidal-scale physics bridge the gap between structural biology, which gives atomistic detail but little time evolution, and systems biology, which models whole-cell time scales but can abstract away spatial effects entirely. Modeling at this colloidal scale led to recent discovery that physical transport regulates some intracellular processes, such as translation elongation in E. Coli. It was recently hypothesized that the nucleoid plays a central role in the organization of macromolecules in the cell, but experimental verification by tracking macromolecular motion is challenging. In the present work, we study the colloidal hydrodynamics and organization of biomolecules migrating through and surrounding the bacterial nucleoid, with a focus on its structure as a porous medium that acts as a sieve and dynamic regulator by screening migration by size and hindering the diffusion of cellular biomolecules. To do so, we developed a computational model of a simple bacterial cell that explicitly represents the nucleoid, the cell membrane, and macromolecules diffusing inside and outside the nucleoid. We tracked detailed trajectories, diffusion, and distributions of biomolecules in cytoplasm and how these are affected by macromolecular crowding, size polydispersity, and physical properties of the nucleoid, such as its density, volume, and porosity. We find spatially heterogeneous organization and particle dynamics that help explain intracellular processes such as protein polarization, translation-elongation, and the diffusion of lipids and RNA into the nucleoid. |
Tuesday, March 15, 2022 5:24PM - 5:36PM |
K20.00013: Hydrodynamic simulations of bacterial swarms highlight the role of cell morphology and cell-cell interactions on emergent patterns Joshua Tamayo, Arvind Gopinath Swarming, a multicellular mode of flagella-based motility observed in many bacteria species, enables coordinated and rapid surface translocation, expansion and colonization. Swarming bacteria display collective features such as persistent aligned flocks, fluctuating velocity fields, and significant vortical structures; these striking patterns have all been observed previously in experiments on swarming bacteria. We explore the roles played by cell shape, direct cell-cell interactions and fluid-mediated hydrodynamic interactions in the onset and maintenance of these structures. Using agent-based simulations of synthetic bacteria modeled as self-propelling high aspect ratio dipolar rods, we explore the effects of geometry, bacterial activity and density on the emergence of flow patterns. High aspect ratios and reduced hydrodynamic interactions yield more persistent rafts and clusters. Conversely, increased hydrodynamic interactions yield reduced cluster sizes but high vorticity and pressure flow gradients. We find that hydrodynamic and steric interactions compete, each differently impacting the role of cell morphology. Our results motivate further studies elucidating how mixing, genetic drift, cell motility, and adaptation may be impacted by cell-cell interactions. |
Tuesday, March 15, 2022 5:36PM - 5:48PM |
K20.00014: Robust mechanics of ameboid cells leading to emergence of self-tuning, biohybrid microtransporter. Setareh Sharifi Panah, Robert Grossmann, Valentino Lepro, Oliver Nagel, Carsten Beta Targeted delivery is one of the key limits of precision medicine, a prime challenge in today’s medical science. Inspired by the motility of leukocytes, we introduce a biohybrid microtransporter with crawling ameboid D.discoideum cells acting as the active element. The microtransport process begins once a motile cell meets a cargo. The dynamics of the resultant two body system is dictated by the cargo size and can possibly spread faster than individual cells in the absence of cargo. |
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