The overarching goal of this direction is to experimentally and theoretically exploit mechanical deformation as a new design space to program particle transport in soft active materials by understanding the large deformation, polymer-network microstructure evolution, reversible particle-polymer interactions, and hopping diffusion of particles across multiple length and time scales. Figure 1 illustrates the strain-programmable particle transport in one emerging soft active material, end-linked star-shaped (ELSS) tough hydrogel, recently exploited in my group. Particles with controlled diameter d diffuse through a layer of ELSS tough hydrogel with controlled mesh size ξ. As a tensile stretch λ is applied on the hydrogel, the hydrogel reduces in thickness and expands in area, enlarging its mesh size and stretching its individual polymer chain, which modulates the particle diffusivity D(λ) by engineering the strain-dependent energy barrier U(λ,d/ξ) experienced by particles for hopping diffusion from initial cage transiting to its neighboring final cage.

The overarching goal of this direction is to uncover the strain-dependent and temperature-dependent strain-induced crystallization, synergistically modulating the processes of phase change and phonon transport in a series of end-linked star-shaped polymers with controlled topological defects towards efficient solid-state elastocaloric cooling. Figure 2 schematically illustrates strain-induced crystallization (SIC) in an end-linked star-shaped polymer (ELSP) with controlled topological defects including cyclic loops and dangling chains, exhibiting a solid-state elastocaloric cooling characterized by adiabatic temperature change . As the ELSP is subjected to an instantaneous tensile stretch , partial amorphous polymer chains transform into crystalline domains, causing a temperature rise due to the phase change. When the stretch is instantaneous released, these crystalline domains revert to amorphous polymer chains, causing a temperature drop . Although solid-state elastocaloric polymers have recently been an emerging focus of study, the impact of topological defects on their elastocaloric performance remains largely unexplored. 

In-situ bioelectronics, a rapidly evolving field focusing on the development of implantable/injectable/ingestible electronic devices that can operate within the body and seamlessly interact with biological systems, has the potential to revolutionize the field of medicine in a variety of ways, such as real-time monitoring, personalized diagnosis, and targeted therapies. However, interfacing electronic components and biological systems is extremely challenging due to their fundamentally contradictory properties. Hydrogel, polymer networks infiltrated with water, shares similar mechanical and physiological properties as biological tissues, therefore exploited as an ideal material candidate to form long-term, high-efficacy, multi-modal interfaces between electronic components and biological systems. An emerging class of in-situ bioelectronics that combine hydrogel technologies with electronic components to create devices that can interact with harsh environments within the body, which we define as in-situ hydrogel bioelectronics, hold great promise for potentially addressing the limitations faced by existing in-situ bioelectronics. Specifically, we are interested in developing electrical tissue adhesive, that can rapidly and robustly adhere electronic devices (e.g., electrochemical biosensors) with biological tissues, enabling strain-insensitive physiological monitoring. 

The perception and manipulation of soft and fragile objects, such as living biological organisms, fragile food items, and flexible electric devices, are crucial in modern robotics, but have been rarely achieved within current robotic systems. However, existing vision-based tactile robots primarily focus on the perception and manipulation of rigid objects, lacking the capability to accurately interpret the physical interactions between the robot and soft or fragile objects accuracy. This leads to an inherent gap between robotic tactile perception and human haptic sensing. The overarching goal of this direction is to develop high-performance vision-based tactile gel-robots that can perceive, visualize, and interpret robot-object interactions, thereby enabling tactile-reactive grasping of soft and fragile objects through system integration and control design.