Research overview

The Yang Research Group aims to develop next-generation bio-interactive implant systems by multiscale design and assembly. The development involves the molecular design and engineering of building blocks (monomers, molecules, oligomers) for specific bio-interactive functions (~ nm), polymer architecture and topology design for desired mechanical properties (nm → μm), and macroscopic assembly for multifaceted functions and properties (~ cm). The success of the research will enhance safety, tissue compatibility, implant longevity, and therapeutic efficacy in long-term implantation. The new implants will also be integrated with either mature or emerging medical device technology to augment the performance and create new bio-sensing modalities.
 
Prior and current research projects

Modular design of bio-functional implants

Implants need to perform designed functions to interact with the biological system and also need to mechanically comply with the target tissue and endure the dynamic body motion. Combining optimal functional performance and desired mechanical properties in implants is important but is a persistent challenge. We develop a modular system to decouple the design of surface functions and bulk mechanical properties, using a multiscale polymer brush coating strategy. This platform technology has enabled tough and anti-fibrotic hydrogel implants with stiffness varying by orders of magnitude. [READ MORE]

Molecular topology design for wet adhesion

Strong adhesion with soft, wet hydrogels (both synthetic and biological) is important for a range of biomedical applications but is challenging, owing to abundant water molecules in the system that cannot carry loads. We illustrate that the synergy of chemistry of bonds, mechanics of dissipation, and topology of connection is fundamental to achieving strong adhesion. In particular, we pioneered the molecular topology design strategy and designed various topologies to enable adhesion between hydrogels with diverse biomaterials. We are currently developing bioadhesive implants that not only maintain stable in vivo adhesion but also match the mechanical properties of target tissues. [READ MORE]

Mechanical design and control for stable and durable implants

Hydrogels as tissue-mimetic materials have long been used in biomedical applications. Yet, the weak mechanical properties and unstable mechanical behaviors limit their use and lifetime in the complex body environment. Fracture, fatigue, hydrolytic degradation, and surface instabilities have been observed as common failure modes of hydrogels. The causes stem from the coupling of bond chemistry, material deformation, and interactions with the body fluid. We perform experiments, modeling, and simulation to investigate the underlying mechanisms and devise strategies to mitigate these issues. [READ MORE]