Date of Award

Spring 1-1-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Franck Vernerey

Second Advisor

Jiangliang Xiao

Third Advisor

Rong Long

Abstract

Hydrogels are networks of polymer chains that are capable of absorbing solvent to become gel-like elastomeric materials. One common observation is the formation of patterns on the stimuli-sensitive gel during the phase transition from swollen to shrunk phase. Our research investigates the mechanics behind gel blebbing; when a temperature-sensitive hydrogel encounters a sudden temperature change, multiple ballon-like bubbles can be seen forming on the gel surface during its shrinking phase. The previous researches established that the surface patterns are the result of an impermeable membrane forming on the surface, creating a surface layer which traps the solvent inside and causing bubbles to inflate. However, the details and kinetics of this inflation of blebs, as well as how neighboring blebs interact with each other, have not been fully understood. In this paper, we first propose a single-bleb system, which explains how delamination and adhesion of its surface layer caused by the internal pressure change could affect the profile of a bleb. Next, we show how we can adapt this model to a multi-bleb system on a large scale surface, and how interactions between blebs could be simplified as “tunnels” transporting solvent between them. We also discuss how changing bath temperature and gel crosslink density could affect this profiles of blebbing according to our theory, then showing how this model aligns with data from our experiments using \textit{Polyacrylamide} hydrogels. We hope this research can provide more understanding of soft materials, such as soft robots and complex biological materials.

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