ABSTRACT: Soft bio-interfacing electronics inspired by human skin and built upon electroactive polymer networks promise to transform healthcare by enabling real-time health monitoring and timely medical treatment. However, the grand challenge lies in achieving molecular-level control over material macroscopic properties, which requires both novel molecular designs and the understanding of fundamental physics that governs polymer network behaviors at multiple length and time scales. Despite the difficulties, such de novo design capabilities can largely push the boundaries of material properties for addressing current limitations of bioelectronics toward clinical translation, including poor functional performance, unreliability and invasiveness. In the first part, I will introduce my PhD work on designing a generalized molecular engineering platform that integrates all desired properties into a single semiconductor material for skin-inspired transistors, including high electrical performance, mechanical reversibility, manufacturing compatibility, and environmental stability. Leveraging the encoded reactivity difference, a rationally designed rubber matrix precursor enables the well-controlled percolation process of a double-network semiconductor film. Built on the system, a surface-tethered molecular protection layer with unique nanostructures is further developed to significantly retard water-induced electrical degradation. In the second part, I will discuss my postdoctoral work on developing a quantitative understanding of the molecular mechanisms for the non-linear mechanical responses of dynamic polymer networks. This is enabled by applying a rheo-fluorescence setup to directly see and quantify bond breakage under shear. We highlight the importance of topology evolution in dictating shear thinning behaviors, which can be controlled by bond kinetics and junction functionality. I will conclude the talk by sharing my vision of integrating the perspectives of polymer network physics to innovate the molecular designs of bioelectronic materials that are fully adaptive to human bodies.

BIOSKETCH: Yu Zheng is currently a postdoctoral researcher working with Professor Bradley Olsen in the Chemical Engineering department at MIT. She applies custom-built characterization tools and rational molecular designs to uncover the fundamental physics of polymer networks. In 2022, she received her PhD in Chemistry from Stanford University with Professor Zhenan Bao. Her dissertation research focused on designing semiconducting polymers and organic field-effect transistors for skin-inspired electronics, with great potential for building wearable and implantable healthcare systems. She obtained her BS in Chemistry from Nankai University in China and completed her BS thesis as a visiting undergraduate researcher at MIT. Her research culminated in numerous honors, including Clarivate Highly Cited Researcher 2024, IUPAC-Solvay International Award for Young Chemists, MIT Rising Stars in Chemical Engineering, and ACS POLY Award for Excellence in Graduate Polymer Research.