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Author ORCID Identifier
Campus-Only Access for Five (5) Years
Doctor of Philosophy (PhD)
Polymer Science and Engineering
Year Degree Awarded
Month Degree Awarded
Ryan C. Hayward
Polymer and Organic Materials
This thesis broadly aims to examine how different surface instability modes compete with each other across various length scales and to apply the resulting fundamental understanding to enable switchable liquid/gas permeation and electrical sensing devices. To this end, Chapter 2 describes a new model for the crease nucleation and growth phenomenon. There have been discrepancies between experiments and theories in critical strains of creasing, especially for systems with high elastocapillary number. In this chapter, we resolved the discrepancy by verifying our new model, which properly takes the surface tension effects into account. Chapter 3 describes acceleration induced surface instabilities. Although wrinkling frequently appears in a bilayer system, it has rarely been observed in a single layer system. In this chapter, we demonstrated rotational acceleration induced wrinkling instabilities on the surface of a single layer gel. Chapter 4 discusses the interplay between surface instability modes originating from a patterned bilayer with characteristic length-scales comparable to those of the instability modes. While applications, such as flexible electronics, have surfaces with in-plane heterogeneity (e.g. metal electrode patterns on PDMS), a fundamental understanding of surface instabilities with in-plane heterogeneity have not been understood well. In this chapter, we successfully controlled critical strains, locations, and types of surface instabilities by changing the micro-pattern geometries, leading to a rich set of surface topographies composed of multiple surface instability modes. Chapter 5 describes the effects of geometrical singularities in the form of notch structures on the development of surface morphology under compression. Although creasing leads to reversible surface self-contact, its applications are limited partly due to the large activation strain required for the crease formation and the difficulties in controlling crease position. In this chapter, reversible surface self-contact was induced by the stress concentration associated with notch structures, and mechanically gated electrical switches with small and tunable activation strains and high on/off ratios were demonstrated. Chapter 6 discusses the fabrication of devices for switchable liquid/gas permeation and electrical sensing and their performance. Devices consisting of large active area surfaces with impermeable conductive patterns were fabricated, which enabled switchable liquid/gas permeation and electrical resistivity under mechanical compression.
Ouchi, Tetsu, "COMPETITION BETWEEN WRINKLING, BUCKLING, AND CREASING INSTABILITY MODES ON THE SURFACES OF SOFT MATERIALS AND PATTERNED BILAYERS" (2019). Doctoral Dissertations. 1558.