arXiv subjects

Daisuke S. Shimamoto

Publications and source records attributed to Daisuke S. Shimamoto.

6 recordsLinked to original sources

arXiv2026

Topology-defined computation in knitted textiles

Mechanical computation, in which logic functions are realized through deformation rather than electronics, has been demonstrated in systems such as origami, kirigami, and mechanical metamaterials. In these systems, logic states and functions are typically determined by geometry and material properties, making it sensitive to deformation and imperfections. Here we introduce a mechanical computing architecture in which logic is defined by topology rather than geometry. The circuit is realized as a knitted textile formed from a single continuous yarn, where information is encoded in the topology of stitches and processed through controlled unraveling. By discretizing the textile into a lattice of interacting cells, we construct topological propagation rules that implement universal logic operations, including NOT, AND, and OR gates, as well as a half-adder. Experiments demonstrate that the logical output is robust against geometric deformation, while mechanical factors affect only if the computation can be executed. These results establish topology-defined computation as a model for information processing in textiles and other reconfigurable physical systems.

cond-mat.soft↗

arXiv2026

Power-law molecular-weight distributions dictate universal behaviors in highly polydisperse polymer solutions

Polydispersity is a universal feature of synthetic polymers and biological molecules in the cytoplasm. However, its quantitative impact on collective behavior remains poorly understood because conventional metrics, such as the polydispersity index, fail to capture broad, non-Gaussian size distributions. Here, we develop an experimental platform in which polyethylene glycol (PEG) solutions are engineered to follow tunable power-law molecular-weight distributions spanning an extensive range, from $M = 1$ kg/mol to $10^{4}$ kg/mol. By systematically varying the $M$ distribution exponent $a$, we identify a robust regime ($1 < a \lesssim 2.5$) in which the viscosity scaling exponent in the entangled regime, the overlap concentration $c^{\ast}$, and the entanglement concentration ${c_{\mathrm{e}}}$ all exhibit pronounced maxima that exceed monodisperse limits. This amplification minimizes as the upper cutoff $M_{\max}$ is reduced, with the system approaching monodisperse behavior. The enhanced rheology arises from a competition between long-chain-dominated entanglement and short-chain-mediated void filling, demonstrating that the whole shape of the molecular-weight distribution plays a decisive role. Consequently, these collective behaviors cannot be reproduced by simply tuning the average molecular weight. Together, our results establish the power-law exponent $a$ as a quantitative control parameter that links polymer entanglement, soft packing, and molecular crowding in highly polydisperse systems.

cond-mat.soft↗

arXiv2025

Topological Defect Propagation to Classify Knitted Fabrics

Knits and crochets are mechanical metamaterials with a long history and can typically be produced from a single yarn. Despite the simplicity of the manufacturing process, they exhibit a wide range of structural configurations with diverse mechanical properties and application potential. Although there has been recent growing interest in textile-based metamaterials, a rigorous topological characterization of what makes a structure knittable has been lacking. In this paper, we introduce a general criterion based on topological constraints that distinguishes knits and crochets from other textile structures. We demonstrate how the introduction of topological defects and their propagation makes this classification practical. Our approach highlights a fundamental link between manufacturing processes and structural fragility. Within this framework, we show how the rationalization of defect propagation unlocks the design of fabrics with controllable resistance to damage.

cond-mat.soft↗

arXiv2024

Compression Causes Expansion and Compaction of the Jammed Polydisperse Particles

This study focused on the expansion in polydisperse granular materials owing to mechanical annealing, which involved compression and decompression. Following minor annealing, the polydisperse systems exhibited compaction as well as the systems having uniform-sized particles. However, following extensive annealing, only the polydisperse systems were observed to expand. Pressure history and structure analysis indicated that this expansion results from the size segregation of the particles. We attribute this segregation to particle-size-dependent effective attraction. The results of this study highlight the strong history dependence of the packing fraction and structure in polydisperse particles and reveal a potential-energy-driven segregation mechanism.

cond-mat.soft↗

arXiv2024

Marangoni droplets of dextran in PEG solution and its motile change due to coil-globule transition of coexisting DNA

Motile droplets using Marangoni convection are attracting attention for their potential as cell-mimicking small robots. However, the motion of droplets relative to the internal and external environments that generate Marangoni convection has not been quantitatively described. This study used an aqueous two-phase system (polyethylene glycol (PEG) and dextran) in an elongated chamber to generate motile dextran droplets in a constant PEG concentration gradient. We demonstrated that dextran droplets move by Marangoni convection, resulting from the PEG concentration gradient and the active transport of PEG and dextran into and out of the droplet. Furthermore, by spontaneously incorporating long DNA into the dextran droplets, we achieved cell-like motility changes controlled by coexisting environment-sensing molecules. The DNA changes its position within the droplet and motile speed in response to external conditions. In the presence of Mg2+, the coil-globule transition of DNA inside the droplet accelerates the motile speed due to the decrease in the droplet's dynamic viscosity. Globule DNA condenses at the rear part of the droplet along the convection, while coil DNA moves away from the droplet's central axis, separating the dipole convections. These results provide a blueprint for designing autonomous small robots using phase-separated droplets, which change the mobility and molecular distribution within the droplet in reaction to the environment. It will also open unexplored areas of self-assembly mechanisms through phase separation under convections, such as intracellular phase separation.

cond-mat.soft↗

arXiv2024

Preparation and observation of jammed particles with power size distribution

Several materials, such as rocks, powders and molecules, are multi-component systems. However, compared to single-component systems, it is difficult to understand the physical component. In this study, as a coarse-grained model for powders with extremely large size variations, we experimentally and numerically filled circular particles with a power size distribution and investigated their structure at the jamming transition point. In the experiment, oil in water droplets following a power size distribution were created, and then we constructed a model with steady injection and fracture to explain the size distribution. In numerical calculations, the dependence of the packing structure on the exponent of the particle size distribution was investigated. The existence of fractal structure with cutoffs was experimentally and numerically found from the structure factor. Numerical calculations show that the area fraction of rattlers is almost independent of exponent, but the number fraction is significantly dependent.

cond-mat.soft↗