Alfred J. Crosby, Ph.D.
Associate Professor
Polymer Science & Engineering Department, University of Massachusetts Amherst

Lessons from Nature: Adhesion and Structure

Nature provides awe-inspiring lessons in designing materials structures from simple building blocks to achieve necessary performance. In these designs, ubiquitous forces are utilized to impart control of both structure and performance. For example, forces associated with differential growth lead to the formation of complex structures, such as fingerprints. Likewise, van der Waals and capillary forces are used by geckos to achieve a unique balance of adhesion and locomotion through a differentiated hierarchy in their foot structure. In this presentation, we present two vignettes that represent broader efforts within our research group to learn from Nature not only in the design of materials but also in concepts that lead to fundamental understanding of materials properties. First, we describe how the same balance of materials properties and geometry that control draping in a thin film can be advantageous for the hierarchical design of reversible adhesives. We demonstrate how smooth interfaces integrated into a thin, flexible structure can lead to a robust balance of high maximum force strength in multiple loading geometries with minimal force of release in other geometries. Second, we describe how elastic instabilities, such as wrinkling and folding, can be used systematically to define surface structures with discretized length scales, permitting robust control of adhesion forces. Both stories present important lessons not only in terms of adhesion but also in the fabrication of materials structures for a wide range of technologies.