Bio

A.B. from Harvard College in Cambridge, MA in 1971; Ph.D. in Biochemistry from Duke University in Durham, NC in 1976; Postdoctoral work at the University of Copenhagen among other institutions. Professor for 12 years at the University of Delaware in the Chemistry and Marine Studies programs before moving to UCSB in 1998. Dr. Waite was elected a Fellow of the American Association for the Advancement of Science in 2009 and is co-leader of IRG-1 for the new Materials Research Science & Engineering Center (MRSEC) at UCSB funded by NSF.

Research

Grand Challenge in Adhesion

A fundamental challenge in materials science is engineering durable adhesive bonds in a wet environment. Most synthetic adhesive systems suffer significant deterioration, even complete failure, in the presence of moisture, which in its broadest sense, ranges from surface hydration to immersion in body fluids or seawater. The long-term research goal is to develop the fundamental design principles involved in bio-adhesion, achieve translation to synthetic systems, and pioneer a systems approach to wet bonding that spans nano- to macroscale dimensions.

Overall Background and Goals

Water commonly subverts adhesive performance, and this is well understood in terms of the effect of hydration on interfacial energies. To the extent that the interfacial ingress of moisture is responsible for much adhesive bond deterioration, clean-room technology today is capable of engineering moisture-resistant covalent bonds between an adhesive and an underlying solid surface, though at considerable effort and expense. In contrast, the technology for adhering to surfaces underwater or in chemically-hostile environments is much more limited, yet these limitations do not appear to restrict the wet adhesion of marine organisms. Mussels, for example, routinely stick to all kinds of surfaces underwater using complex fluids that spread spontaneously and exhibit strong reversible interfacial bonding and tunable cross-linking. Similarly, the sandcastle worm secretes microdroplets of adhesive to build a tube-like burrow from sand grains and other particles. The development of a complete, molecular-based understanding of bio-adhesion and its translation to synthetic systems would not only significantly impact moisture-limited performance of current adhesives and coatings, but open up new avenues of materials research in biomedical implants/coatings, infiltration-processed composites, and hydrocolloid clay-based nanocomposites.

The working hypothesis of our research is that formulating a practical wet adhesive requires the creative translation and fundamental understanding of two prominent features of marine bioadhesives: i) the role of dense surface-active polyelectrolyte fluids (coacervates) that remain phase-separated from water and undergo triggered solidification, and ii) the presence of polymer functionalities (e.g. Dopa) that provide energetic wet surface bonding.

According to this scheme, the coacervate is formed by mixing different water-soluble components, phase separated from the aqueous media and spread over target surfaces, thereby enabling proximity and binding between Dopa and the surface. Following these events, the coacervate film undergoes a triggered crosslinking reaction leading to hardening and adhesion. Successful translation of wet bioadhesion therefore depends on harnessing interfacial chemistry, micromechanics, and microfluidics to understand the material systems at multiple length and time scales. With its historical prowess in interdisciplinary science and engineering, UCSB provides impressive resources to capture and implement innovative biodesign concepts to produce predictive models, novel processing strategies, and delivery systems for wet adhesion. The Waite Lab has the expertise in adhesive biochemistry, but we increasingly collaborate with the Han Lab (Chem Dept) for sensitive probing of solid/solution interfaces and phase boundaries, and with the Israelachvili Lab for fundamental static and dynamic surface forces experiments. These collaborations have already led to significant insights into the hydration, rheology, and interfacial chemistry of adhesive and cohesive polyelectrolyte proteins. Further collaborations are underway with the Hawker Lab (Materials Department) to examine of the synthesis, phase behavior, and physical properties of analogous novel synthetic polyelectrolyte complexes, and with the Valentine and Begley Labs (Mechanical Engineering Dept) to study the time dependent effects of adhesive mixing and deposition in natural and synthetic systems.