Topology optimization and physical realization of magnetically active soft materials: from reprogrammable metamaterials to biomedical robots

Magneto-actuated soft materials have garnered growing interest due to their ability to undergo rapid, remote, and controllable deformation under applied magnetic fields. These materials have shown promise across a range of applications, including soft robotics and biomedical devices. In particular, one type of magnetic soft materials, made of a soft elastic matrix embedded with magnetic particles that can retain high remanent magnetization, offer exceptional programmability and flexibility. As an initial exploration in the design optimization for this material, we develop a comprehensive topology optimization framework for magnetic soft materials to guide the rational design with programmable actuation under large deformations. This framework simultaneously optimizes the material topology, remanent magnetization distribution (selected from several candidate directions), and external magnetic field directions, enabling the design of soft robots and actuators. While the current implementation utilizes a reduced-order magnetic soft material constitutive model, the framework remains generalizable to more complex constitutive models. Building on this foundation, we extend the framework to enable magneto-actuated reprogrammability, where a single design can exhibit a desired deformation under purely mechanical loading and transition to a different response when subject to both mechanical and magnetic stimuli. We demonstrate this capability experimentally using one of our optimized designs. We also discover magnetically active structures showcasing a broad spectrum of tunable buckling mechanisms with experimental investigations, including programmable peak forces and buckling displacements, as well as controllable mechano- and magneto-induced bistability. To further expand the design space and facilitate designs that are highly compatible with advanced additive manufacturing techniques such as direct-ink-writing, we develop a parametrization method that enables designs with spatially continuous magnetization transitions and locally arbitrary magnetization orientations. The optimized designs are highly compatible with the direct ink writing process, as demonstrated through successful fabrication and experimental validation. In addition, we expand the design framework for magnetic soft materials with electrets (immobile charges) inducing coupled electric field. These magnetoelectric materials generate electric output through magnetically induced deformation and deformation-induced charge redistribution. We successfully optimize these structures for both charge generation and target deformation modes. We present several application-driven designs including therapy robots that deliver combined mechanical and electrical stimulation. We conduct tailored fabrication and experiments for optimized magnetoelectric designs.Additionally, we develop multi-functional devices capable of providing target deformation and electricity generation, potentially for self-powering or self-sensing. As a proof of concept, we demonstrate such designs can generate sufficient electric power to power an LED. These results highlight the potential of our framework for next-generation magneto-mechano-electric biomedical devices.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Zhao, Zhi

Contributors dc:contributor

• Zhang, Xiaojia
• Saif, Taher
• Lopez-Pamies, Oscar
• Hu, Yuhang

• Topology optimization
• Magnetic soft material
• Reprogrammable metamaterial
• Biomedical robots

Statement dc:rights

• Copyright 2025 Zhi Zhao

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132732

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132732