(4hb) Adaptive Polymer Electronics: Multiscale Design and Mechanism Understanding

My research interest lies in precisely controlling the multiscale assembled structure of electroactive polymers, and understanding their dynamics and transport behaviors. This approach aims to create adaptive electronic materials capable of interfacing with biological systems in an efficient, long-term reliable and minimally invasive manner. Polymeric soft bioelectronics promise to transition our society into a new paradigm of personalized healthcare, where wearable and implantable devices enable real-time health monitoring and timely medical therapies. Towards these goals, the grand challenge lies in achieving predictable material designs based on fundamental understanding of molecular mechanisms underpinning macroscopic properties, where polymer networks exhibit complex dynamic behaviors across multiple length and time scales. Despite the difficulties, such de novo design capabilities can largely push the boundaries of material properties for addressing the current limitation of bioelectronics towards clinical translation, including functional performance, stability and invasiveness. My research aims to leverage fundamental principles of polymer chemistry and physics to design the structure of electronic materials at molecular and microscopic level. We will study the structural dynamics and molecular transport of these synthesized materials that directly dictate time-dependent macroscopic properties and encode the mechanism understanding into iterating material design. Through enabling molecular-level control of network macroscopic properties, we aim to develop mechanically compatible, environmentally stable and electronically active materials and interfaces that are adaptive to various long-term operation scenarios of bioelectronics.

Research Experience:

Molecular design of polymer semiconductors for skin-inspired electronics, Department of Chemical Engineering, Stanford University (advised by Zhenan Bao)

My doctoral research focused on developing molecular design approaches to tackle critical challenges for deploying polymer semiconductors (PSCs) in soft and stretchable electronic devices, achieving unique combination of high mechanical reversibility, manufacturing compatibility and environmental stability. Specifically, I designed azide-terminated polybutadiene precursors that can undergo self-crosslinking and crosslinking with PSCs in finely controlled ratio leveraging the encoded reactivity difference. In the composite film, the semiconductor maintains charge transport pathways due to optimized aggregation while covalently embedded within the in-situ formed rubber matrix that provides high mechanical reversibility. Additionally, taking advantages of solvent resistance and photo-patternability of such crosslinked semiconductor, I demonstrated its compatibility with solution-processed multilayer circuits manufacturing. Moving forward, a molecular protecting method was developed to significantly improve PSC’s stability in transistors that operate in harsh environments. This involves covalent functionalization of fluoroalkyl-chains onto PSC film surface to form densely packed nanostructures with remarkable ability to block water absorption and diffusion. The molecular protection layer exhibits orders of magnitude lower water permeability than that of current encapsulation materials used for stretchable electronic devices.

Understanding the molecular origin of non-linear rheological responses in associative polymers, Department of Chemical Engineering, Massachusetts Institute of Technology (advised by Bradley D. Olsen)

My postdoctoral research has been focusing on leveraging optical-mechanical characterization tool and systematic molecular interactions programming to understand the molecular-level dynamic behaviors of polymer networks under mechanical deformation. Specifically, with a custom-built rheo-fluorescence set up, the amount of bond breakage and reformation in a series of rationally designed model end-linked associative polymers is quantified in real-time with their shear thinning behaviors, based on a fluorescence quench transition when associative phenanthroline ligands bound with transition metal Ni²⁺. Our results highlight the importance of bond re-association kinetics in dictating shear-induced network topological translation from bridging chains to dangling ends and elastically inactive loops. A thermodynamic model is further developed to map the entire distribution of chain configuration and network relaxation time, which matches with the experimental trend. The obtained new understanding will pave the way for refining current transient network theories and can be broadly leveraged to advance inverse design of polymeric materials with desired structural dynamics and mechanical properties for different application scenarios.

Teaching Interests:

Based on my chemistry background and chemical engineering research training, I am excited to teach core undergraduate courses, including thermodynamics and kinetics of chemical reactions. I also look forward to teaching graduate level courses related to polymer science and engineering, and soft matter. Leveraging my research interests and expertise, I am further enthusiastic in developing elective graduate level courses, such as polymer electronic materials and devices for healthcare. The coursework will involve both fundamental and application aspects of functional polymeric materials, with the goal of preparing next-generation scientists and engineers to solve pressing challenges in the world.