Date of Award
Chemistry and Biochemistry
Gas-diffusion Barrier, Impermeable Soft Electronics, Light-emitting Devices and Sensors, Materials and Surfaces, Stretchable Electronics, Transparent Butyl Rubber
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This dissertation reports a diverse range of new components for the fabrication of soft flexible, stretchable and wearable electronic devices. The components investigated spans design and development of a new elastomer, layered elastomeric material, investigation and modification of surface chemistries, and development of new techniques for fabrication of stretchable, conductive composites using nanomaterials and metals. Simple, low-cost, benchtop techniques for the fabrication of the functional materials has been a strong focus of the work reported in this dissertation. Chapter 2 reports the development of a new transparent formulation of a renowned elastomer, butyl rubber, that enables its use in stretchable electronics applications. We design a new compression molding method to prepare highly smooth and transparent butyl rubber (T-IIR) substrates. We demonstrate the T-IIR protection to sensitive electronic materials from degradation and corrosion by oxygen and moisture to extend the lifetimes of stretchable devices. The demonstrated benefits positions T-IIR as an important elastomer for future generation of impermeable stretchable electronics. Chapter 3 examines the surface properties of T-IIR reported in Chapter 2 and reports methods to modify the surface chemistry of T-IIR to enable the deposition of electronic materials. This report advances the new elastomer from being a mere encapsulant to a substrate for direct device fabrication on its surface. As a proof of concept, we demonstrate the deposition of stretchable gold films on the organosilane-modified surface of T-IIR. Chapter 4 expands upon the work presented in Chapter 3 and reports the fabrication of a multilayered elastomeric composite built upon T-IIR. The properties of the composite enables the deposition of stretchable metal films, while T-IIR prevents degradation from gases and water vapor when the composite/metal is used in electronic devices. We demonstrate the fabrication and long lifetime performance of wires, circuits and light-emitting devices using metal films on the T-IIR-based elastomeric composite as electrodes. Chapter 5 investigates a low-cost, scalable technique for fabrication of transparent, stretchable and conductive films on elastomer using electrostatic self-assembly of functionalized nanomaterials. Layer-by-layer assembly of functionalized single-walled carbon nanotubes (SWNTs) provide precise control over transparency and conductivity. We demonstrate these films on elastomer, in strain sensor and light-emitting device fabrication. Chapter 6 demonstrates another class of conductive material, liquid metal alloys, for fabrication of soft elastomeric composites for large-area electronic devices. The method focuses on the confinement of liquid metal alloy within elastomeric matrix while taking advantage of the free-standing liquid metal properties. The work examines the use of soft conductors as interconnects to measure conductivity of thin films and investigates their use as electrodes in light-emitting devices.
Vohra, Akhil, "New Elastomeric Materials and Functional Composites for Stretchable Electronics" (2017). Electronic Theses and Dissertations. 5955.