Date of Completion

8-22-2018

Embargo Period

8-15-2020

Keywords

bio-inspired materials; stimuli responsive materials; wrinkled device; mechanochromism;

Major Advisor

Luyi Sun

Associate Advisor

Richard S. Parnas

Associate Advisor

Mu-Ping Nieh

Field of Study

Materials Science

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Smart soft materials, which are commonly integrated with function-oriented surface engineering and substrate configuration, capable of reversibly changing transparency, fluorescence, coloration, are playing critical part in the emerging optical/electronic applications. Inspired by the vivid displaying tactics in marine life, a series of intriguing bilayer or multi-layer devices based on a rigid thin film tightly bonded to a soft stretchable substrate was achieved in this dissertation. These devices exhibit versatile multi-stimuli responsive characteristics which can dynamically change their optical properties (such as transparency, fluorescent intensity/coloration, reflective color) as exposed to specific stimulus (such as heat, UV, moisture, electrical field and/or mechanical force). In chapter 2, we developed a deformation-controlled surface-engineering approach via strain-dependent micro-cracks and folds to realize a broad range of mechanochromic devices with high sensitivity and reversibility. In chapter 3, three types of moisture-responsive wrinkled devices are achieved through a single film–substrate system. These dynamics include: 1) completely reversible wrinkles formation; 2) irreversible wrinkles formation I: the initially formed wrinkles can be permanently erased and never reappear; and 3) irreversible wrinkles formation II: once the wrinkles form, they can no longer be erased. These unique responsive dynamics motivate the invention of a series of optical devices triggered by moisture, including anti-counterfeit tabs, encryption devices, water indicators, light diffusors, and anti-glare films. In chapter 4, we develop multi-stimuli responsive chromic units for stretchable interactive electronics through a three-dimensional integration approach with high design flexibility and wide applicability. The resultant highly stretchable interactive electronics are equipped with thermochromic/photochromic characteristics, electrochromic response indicating bias direction, as well as two types of mechanochromic effect with different levels of strain sensitivity. It’s believed that these design strategies can inspire various designs of other highly sensitive and reversible stimuli-responsive smart materials with widespread applications, such as multi-stimuli responsive optical sensor for wearable electronics, encryption devices, energy conservation devices and so on.

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