arXiv subjects

Marie Tani

Publications and source records attributed to Marie Tani.

5 recordsLinked to original sources

arXiv2026

Self-Viscophoresis: Autonomous Motion by Biasing Thermal Fluctuations via Self-Generated Viscosity Asymmetry

Microscale transport often relies on ubiquitous yet intrinsically random thermal fluctuations. Understanding how such fluctuations can be biased into directed motion has long been a central theme of nonequilibrium physics. Here, we introduce self-viscophoresis, a mechanism of autonomous motion based on the rectification of thermal fluctuations in a self-generated nonequilibrium viscosity field. Asymmetric colloidal particles dispersed in a thermoresponsive polymer solution induce local heating under uniform illumination, producing a spatially asymmetric viscosity profile around the particle and resulting in persistent directed motion. To elucidate the physical origin of this behavior, we develop a minimal Langevin model coupling isotropic thermal fluctuations to a dynamically updating temperature-viscosity field. The model shows that viscosity asymmetry anisotropically damps stochastic dynamics, effectively biasing thermal fluctuations into a net drift. It thus reproduces the observed directed motion without invoking deterministic propulsion terms associated with effective potentials or environmental fluid flows. Our results distinguish self-viscophoresis from conventional self-propulsion mechanisms and establish it as a general framework enabling reversible control of both the direction and dimensionality of motion.

cond-mat.soft↗

arXiv2025

Anomalous Enhancement of Yield Strength due to Static Friction

Friction is fundamental to mechanical stability across scales, from geological faults and architectural structures to granular materials and animal feet. We study the mechanical stability of a minimal friction-stabilized structure composed of three cylindrical particles arranged in a triangular stack on a floor under gravity. We analyze the yield force, defined as the threshold compressive force applied quasi-statically from above at which the structure collapses due to sliding at the floor contact. Using singular perturbation analysis, we derive an expression which quantitatively predicts the yield force as a function of the static friction coefficient and a small dimensionless parameter $\epsilon$ characterizing elastic deformation.

cond-mat.soft↗

arXiv2023

Spreading of foam on a substrate

Foam is an industrially important form of matter, commonly deployed to clean objects and even our own skin, thanks to its ability to absorb oil and particles into its interior. To clean a large area, a foam is spread over a substrate, but the optimum conditions and mechanism have been unclear. Here, we study how a foam is spread by a rigid plate on a substrate as a function of spreading velocity, gap height, confinement length, amount of foam and wettability of the substrate. Three distinguishable spreading patterns were found: homogeneous spreading, non-spreading, and slender spreading. It is also found that the dynamics and the mechanism of the spreading can be explained by coupling among dewetting, anchoring, shear stress, viscous stress and yield stress. It is a unique feature of foams, which is not observed in simple liquids and then these findings are also critical for understanding the mechanical response of other soft jamming systems such as cells and emulsions.

cond-mat.soft↗

arXiv2023

Gel-like granular materials with high durability and high deformability

Building materials such as concretes and mortar are formed by solidifying granular slabs. Such materials are often fractured by giant forces such as during earthquakes, leading to the collapse of structures and potentially casualties. One avenue of enquiry to prevent cracking would be to realize a material that can maintain a stable shape without being solidified. Here, we focus on sand grains coated with silicone oil, experimentally investigating the Young's modulus of a granular slab where ordinary grains and the coated grains are mixed in a mixing ratio $\alpha$. It is found that the Young's modulus increases rapidly at $\alpha \ge 0.6$. We use numerical simulation to show that this sudden increase in the Young's modulus is caused by a rigidity percolation transition. Furthermore, we are able to show that granular slabs containing coated sand have outstanding deformability without collapsing under large external stress. We believe this may lead to the development of granular materials that are rigid under usual pressures but deformable under more extreme conditions, such as during seismic activity.

cond-mat.soft↗

arXiv2022

Selective 3-dimensional patterning during phase separation of a continuously laminated layer

Control over the physical properties of materials is ubiquitously required in many fields. One means by which this can be achieved is controlling the internal structure of multi-component materials with an eye to enhancing mechanical properties. Here, we focus on self-organized pattern formation in phase separating materials, where microscopic patterns with a smooth, continuous connection may be realized. We propose a feasible method to control pattern formation using phase separation combined with continuous ``lamination'' of material, when material is continuously and homogeneously layered on top of a base. We find that a random droplet pattern, a lamellar pattern, and a cylindrical pattern are formed depending on the lamination rate $V$. We clarify the dynamics of pattern formation, focusing on the mechanism. This study may lead to the creation of new functional materials through artificial pattern control.

cond-mat.soft↗