CAREER: Wetting and dynamics on soft and swollen polymeric surfaces

Soft and swollen polymers are critical for many areas of science and technology, from biological and synthetic tissues to flexible devices and non-stick coatings. These materials comprise both a solid portion and a fluid portion, making it challenging to predict their behavior. However, understanding how these materials interact with liquids or solids is necessary for the design of advanced applications for national health and prosperity.

This CAREER project supports fundamental research to investigate how soft and swollen surfaces interact with liquid drops in a variety of static and dynamic situations. Insights gained from this work are expected to aid in the development of new biomaterials for healthcare applications and in the design of non-stick coatings for improved drag reduction and anti-fouling.

In addition, this project will support a summer program to provide pre-college and underrepresented students an opportunity to explore and consider STEM-based careers. Moreover, the project will offer an international educational experience for graduate students in the UK to enhance the global research enterprise. The project will train students in the cross-disciplinary area of polymers, surfaces, and mechanics for the future workforce.

Soft and swollen polymers are critical for a wide range of applications, and hence it is important to understand how they interact with other media. The objective of this CAREER project is to provide fundamental knowledge on the relationships between materials-specific properties and the wetting behavior of soft, swollen, and crosslinked polymers. Over the last decade, wetting has been investigated on slippery, lubricant-infused porous surfaces (e.g.

SLIPS) and on soft, crosslinked solids; in both cases, a wetting ridge forms from either the lubricant or the soft solid. However, wetting is not well understood on soft swollen networks, which are crosslinked polymers infused with a fluid. More specifically, it is unclear how the synergy between the swelling fluid and the polymer network governs wetting ridge formation and wetting dynamics.

To investigate how liquid drops wet soft and swollen networks, confocal microscopy, fluorescent dyes, and lateral force measurements will be employed. A range of silicone-based networks combined with a range of swelling fluids will be implemented, which will allow for systematic control over the mechanical properties, the swelling ratios, and the fluid-network interactions.

Experimental results will be theoretically considered by merging fundamental concepts from surface science, mechanics, and polymer science. In addition, soft materials will continue to play a pivotal role in the science and engineering landscape. Broad mentorship of graduate students and a focused seminar series among groups working on soft materials will offer enhanced training for the future workforce.

Moreover, this project will provide graduate students with an enriching international experience in the UK to better understand the global research culture. Expanding on drop-surface interactions, students will travel abroad and explore insect adhesion on soft and swollen surfaces.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.