Date of Award

1-1-2019

Publication Type

Master Thesis

Degree Name

M.Sc.

Department

Chemistry and Biochemistry

First Advisor

Tricia B Carmichael

Keywords

Composites, Polydimethylsiloxane (PDMS), Silica nanoparticles, Stretchable electronics, Thin gold films, Wearable electronics

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Abstract

Stretchable conductors play a fundamental role in wearable electronics as device electrodes and interconnects. Polydimethylsiloxane (PDMS) is conventionally used as the platform for stretchable conductors which are fabricated by depositing a thin layer of gold metal onto the surface. These gold films fail electrically under minimal strains (15-20% linear elongation) due to uncontrolled crack propagation through the metal film. Adding a rough microstructured polymer layer onto the PDMS surface preserves electrical conductivity in metal films to higher elongations of 60% due to the numerous sites for strain localization. However, such heterogeneous layered systems are vulnerable to delamination, leading to device failure. In this thesis, we fabricate a composite layer by combining silane modified silica nanoparticles together with PDMS prepolymer on top of an elastomeric substrate to enable the fabrication of stretchable gold films.

Chapter 2 describes the fabrication and deposition of this composite layer onto an elastomeric substrate for robust interlayer adhesion for the fabrication of stretchable gold films. Changing the loading and dispersity of the particles in the composite layer enables gold films to stretch to 50 - 70% elongations. There is a very linear change in resistance with elongation that is unique to each particle loading creating a tunable system with the opportunity for different strain sensor applications.

Chapter 3 expands on the work in Chapter 2 by examining the effect of dramatically changing the particle size, from 12 nm (Chapter 2) to 300 nm on the organization and structure of the composite surface and the influence on the retention of conductivity with stretching of overlying gold films. By increasing the size of the particles, they associated less with one another and with the polymer resulting in films with less topography and higher resistances upon elongation.

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