Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 143540

143540 - Strain-Engineered Particle Diffusion in Uniaxially Deformed Polymer Networks 

The ability to precisely control particle diffusion holds great promise across diverse modern applications. In the field of medicine, for example, it is essential for drug carriers to release therapeutic agents at a controlled rate on the target site, optimizing therapeutic efficacy and minimizing side effects. In electrical vehicles, the fine-tuning of lithium-ion diffusion plays a vital role in enhancing battery efficiency and lifespan. Furthermore, in environmental engineering, strategic control of particle diffusion is critical for improving the effectiveness of pollution detection and optimizing the efficiency of pollution removal.

Traditionally, the dynamics of particle diffusion in liquid or gas adheres to Brownian motion, following the classical Stokes-Eistein equation. In scenarios where medium properties (i.e., temperature and viscosity) remain constant, traditional approaches face challenges due to limited controllability and adaptivity in tuning particle diffusivity. In contrast, leveraging mechanical deformation on a stretchable polymeric medium for controlling particle diffusion offers inherent advantages. Firstly, the utilization of the polymer network introduces a larger design space, such as the stiffness of polymer chains and mesh size of the polymer networks. For instance, adjusting the stiffness of polymer chains impacts the resistance encountered by particles, and the mesh size of the polymer networks can be tailored to enable the selectivity of particles with diverse sizes. Secondly, employing mechanical deformation allows real-time and on-demand regulation of particle diffusion. For example, adjusting the magnitude and duration of external forces facilitates real-time and on-demand tuning of particle diffusivity, while manipulating the direction of deformation customizes the diffusion path of particles.

In this presentation, we systematically investigate the impact of mechanical deformation on particle diffusion in stretchable soft materials. Particularly, we focus on the particle diffusion in stretchable hydrogels subjected to controlled uniaxial tensile load. We perform fluorescence recovery after photobleaching (FRAP) experiments on uniaxially stretched hydrogels mixed with FITC-dextran to experimentally study the impact of the uniaxial stretch ratios on the diffusivity of particles across various sizes. Our experimental findings reveal an intriguing transition in the relationship between particle diffusivity and stretch ratio, characterized by a monotonic decrease for small particles and a non-monotonic trend for large particles. To explain the experimental observations, we developed a cross-scale mechano-transport theory that integrates nonlinear large deformation of soft materials, obstuction diffusion model and hopping diffusion model of particles. Our theory reveals that particle diffusivity in a stretchable polymer network is governed by two dimensionless parameters: the ratio of particle size to the polymer network’s mesh size and the stretch ratio applied to the polymer network. Through combined experimental and theoretical analyses, we further delve into the synergistic effects involving geometric transformation of polymer networks and energy modulation of polymer chains. This work not only provides the knowledge of mechano-transport mechanism pertinent to a broad range of biological and synthetic soft materials, but also lays a theoretical foundation for developing previously inaccessible transport-based technologies.

Presenting Author: Jiabin Liu Michigan State University

Presenting Author Biography: Jiabin is currently a PhD student in Mechanical Engineering at MSU, supervised by Dr. Shaoting Lin. She joined Lin Research Group in the Fall of 2022 after receiving two Master's degrees in Electrical Engineering at Tsinghua University and Northwestern University. Her research interests include high-performing color-changing soft materials for tactile sensing and particle diffusion in deformed polymer networks.

Authors:

Jiabin Liu Michigan State University
Shaoting Lin Michigan State University