Dynamic Bonds and Mechanical Properties of Tough Hydrogels: Medical Device and Gel Electrolyte Applications

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BACKGROUND. Dynamic bonds, physical or chemical bonds that can be released by external stimuli in a reversible way, are the most fundamental building block for smart soft materials. While individual dynamic bond may be considered as weak, tough hydrogels (fracture energies of ~10,000 J/m2) has been realized by clustering hydrogen bonds or ionic pairs, which also enables reversible adhesion and self-healing. Despite of the technological importance and empirical successes, current understanding on the correlation between these dynamic bond clusters and the mechanical properties of tough hydrogels at its infancy. This problem is partly because of limited capability of existing experimental tools. SOLUTION. Overall objective of PROGRAM 1 is to establish microchannel cantilever sensor, whose vibration being monitored by laser Doppler vibrometer, as a standard tool for studying the dynamic bonds in (hydro)gels. Established for ultrasensitive detection in biosensing, the two additional merits of the method are picoliter sample size and the variety of vibration modes. The short-term objective (3 years) is to validate the microchannel cantilever technology as a tool for quantitative microrheology. In mid- to long-term plan (5 years and beyond), collaborations with polymer chemists, density functional theory experts, and mechanics theoretician will make quantitative correlations between the characteristics of dynamic bonds (such as individual/clustered bond strength and association/dissociation kinetics) and dynamic mechanical properties (time-resolved evolution of complex moduli). APPPLICATION. With a purpose to complement my current research programs on biomedical devices and battery gel electrolytes, PROGRAM 2 is on molecular design of sticky hydrogels with tunable adhesion. The short- to mid-term objective (5 years) is to fabricate hemorrhage suppressing gel pad that can apply quickly and then release on demand. Long-term objective (beyond 5 years) is to integrate wound-dressing or implantable bioelectronics on the sticky hydrogel platform for advanced healthcare devices, which will be realized by converging my whole research activities. IMPACT. Fundamental understanding on dynamic bonds and its impact to mechanical properties is tremendous across all disciplines of soft materials. Molecular design of sticky and tough hydrogels can be translated to traditional technologies such as rubbers, adhesives, and coatings, as well as to emerging technological areas of biomedical devices, drug delivery, and soft robotics. The proposed DG complements my entire research program to become a self-consistent unity with strong scientific foundation. HQPs trained in my unique and highly interdisciplinary research program will have qualities required for engineers in future society, where convergence between disciplines is the key. Scientific/technological discovery and trained HQPs from the proposed DG will evolve academia and industry in Canada and in the world.