IMX Talks - Microparticle-Reinforced Polymers

Nature produces materials with a fascinating combination of stiffness, strength and functionality through energy-efficient, environmentally friendly processes. These remarkable properties arise from the interplay between hierarchical structural organization and spatial variations in composition. Achieving comparable structural and compositional control in synthetic soft materials remains challenging, largely because conventional manufacturing methods differ substantially from those used in biological systems. Natural load-bearing polymer-based materials are often formed through compartmentalization and extrusion-based processing. Elements of these strategies can be reproduced synthetically by formulating soft polymers as capsules or deformable microparticles. However, the resulting granular materials are generally mechanically weak.
In this presentation, I will show how hydrogels and elastomers can be 3D printed by direct ink writing at room temperature and subsequently transformed from viscoelastic granular assemblies into elastic, load-bearing double-network granular polymers. This is achieved by formulating hydrogels or elastomers as reagent-loaded microparticles that are jammed to obtain the rheological properties required for extrusion-based processing. We transform these soft granular structures into elastic load-bearing materials by polymerizing reagents contained within the microparticles to create a stretchable polymer network that interpenetrates the microparticles and covalently crosslinks them. I will demonstrate how stiffness and toughness of these granular materials can be tuned independently and how interparticle interfaces can be leveraged to introduce functionalities, including electrical conductivity. These 3D-printable functional materials have the potential to be used as multi-responsive sensors and soft actuators capable of undergoing programmed deformations.

Bio: Esther Amstad studied materials science at ETH Zurich, where she subsequently completed her doctoral research on the steric stabilization of iron oxide nanoparticles. She then undertook postdoctoral research at Harvard University, focusing on the development of microfluidic devices for applications such as the high-throughput production of monodisperse emulsion drops. In 2014, she joined the Institute of Materials at the École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, as a tenure-track assistant professor. She was promoted to associate professor in 2021. She currently leads the Soft Materials Laboratory (SMAL), where her research focuses on the development of drop- and microparticle-based processing strategies for the fabrication of functional, load-bearing granular polymers, with potential applications in fields including soft robotics.