Transient electronics: Materials, mechanics, and applications

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2018-01-01
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Chen, Yuanfen
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Reza Montazami
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Mechanical Engineering
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Abstract

Transient electronics is an emerging field in materials science that has attracted considerable attention from the scholar community in the last few years. The unique attribute of transient technology is the capability to fully or partially disintegrate after a predefined period of stable operation. Transient electronics have a wide range of potential applications as biomedical implants, environmental sensors, and hardware-secured devices. Biodegradable transient sensors could be dissolved and absorbed into a bio-environment, eliminating complications associated with long-term presence of implanted devices, or secondary surgery to extract implanted devices. Eco-friendly environmental monitoring transient devices could be utilized to collect desired data, then degrade naturally into the surrounding environment, reducing the recollection expenses, and minimizing harmful waste. Self-deconstructing platforms could undergo disintegration and physically remove sensitive information once transience is triggered. Recent developments on transient materials, dissolution/disintegration mechanisms, manufacturing techniques, structural designs, and transient energy storage devices have advanced the functionality, performance, and applicability of transient electronics. Further research on precisely controlled transiency, however, is needed to broaden the applications of transient electronics. Since transient electronics are typically multilayer thin-film structures, to achieve controlled transiency at device level, it is crucial to understand the interfacial interactions among layers of dissimilar materials assembled on one another to form complex transient devices.

This dissertation discusses materials, transiency mechanisms, and applications of transient electronics. Firstly, interfacial interactions among layers of dissimilar materials is systematically studied, revealing the mechanism of transiency achieved by swelling induced disintegration. Following section reports a transient battery utilizing swelling induced transiency as a proof-of-concept application. Lastly, the dissertation presents materials, mechanical properties, and applications of all-organic soft transient electronics.

Firstly, to understand the underlying mechanism of swelling induced transiency, we studied interfacial interactions of a particular case of polymeric substrate with lithium titanate electrode coating layer. The structure is analogous to that of the anode in typical lithium-ion batteries; yet, can be extended to more general cases of soft electronics. This coordinated experimental-analytical-simulation study exhibited formation, accumulation and propagation of swelling-induced stress and fracture through the membrane-coating interface, when in transient mode. Swelling-induced stress as a function of electrode thickness was studied; the analytical data and simulations were verified by experimental results. Moreover, the fragment size of the electrode coating layer as a function of initial defect prevalence and distribution was investigated. The average fragment size was predicted using a combination of experimentally-determined initial defect distribution and finite element method-obtained swelling strain – defect length curve. The predicted average fragment size was found to be in good agreement with the experimental results.

Meanwhile, as an application of swelling induced transiency, a transient lithium-ion battery based on polymeric constituents is presented. The battery takes advantage of a close variation of the active materials used in conventional lithium-ion batteries and can achieve and maintain a potential of > 2.5 V. All materials are deposited form polymer-based emulsions and the transiency is achieved through a hybrid approach of redispersion of insoluble, and dissolution of soluble components in approximately 30 minutes. The reported transient battery could be applied an onboard power for transient electronics.

In addition, a flexible all-organic transient sensor with potential to be applied as epidermal sensor is reported. A conductive conjugated polymer electrode was printed onto a water-soluble polymer substrate with an electrodehydrodynamic jetting printer. The all-organic electrode is partially transient with supportive substrate dissolved completely in water, while the conjugated polymer electrode remains intact. The intact functional electrode layer formed conformal contact with human skin and was applied as an epidermal strain sensor.

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Wed Aug 01 00:00:00 UTC 2018