Recent experimental and theoretical progress on mechanical instabilities of polymer surfaces has provided a good understanding of two fundamental modes of instability: wrinkling, driven by buckling of a stiff film on a soft substrate, and creasing, driven by buckling of the soft substrate itself. However, real material systems found in biological and technological contexts often show a diversity of behaviors that defy explanation based on these simple paradigms alone, due to the greater complexity in terms of both geometry and material properties when compared to the simple model systems that have been carefully studied to date. This project seeks to advance understanding of polymer surface instabilities by developing a comprehensive picture of the landscape of surface buckling modes that occur in elastic bilayers, as parameterized by the mismatch in thickness and stiffness between the two layers, as well as the level of compression felt by each. Experiments will be carried out to quantitatively characterize the onset and development of different instability modes, the mechanisms of transitions between these different states, and the presence of hysteresis and bistability upon cycles of loading and unloading. Comparisons with finite element models will provide further insights into the driving forces for each of these behaviors.
NON-TECHNICAL SUMMARY
Buckling mechanics are central to a wide range of phenomena, ranging from the development of functional structures in biology, to the operation of micro-electromechanical devices in consumer electronics. This project seeks to provide an integrated understanding of the interplay between two fundamental surface buckling modes that are of key importance for polymeric materials. It will provide model experimental systems that offer the potential to improve our understanding of morphogenetic processes in biology and diseases such as asthma, and will also open new routes to technologically applicable materials with switchable properties such as adhesion and optical transparency. The project will also provide mentoring and research opportunities for a diverse group of participants including high school students and teachers, graduate students, and undergraduates. Lasting partnerships with teachers and students from nearby school districts that serve large populations of under-represented minority students will be developed to aid in efforts to diversify the field.
