Recent advances in electronics enable powerful biomedical devices that have greatly reduced therapeutic risks by monitoring vital signals and providing means of treatment. Implantable devices can help us better understand the behavior and effects of various diseases. However, an additional procedure is required to remove the device after an initial implantation. Conventional electronics today form on the planar surfaces of brittle wafer substrates and are not compatible with the complex topology of body tissues. Therefore, stretchable and absorbable electronics are the two missing links in the design process of implantable monitors and in-vivo therapeutics. This thesis presents the challenges, mechanics, and design strategies, behind a potential medical device that (a) integrates with human physiology, and (b) dissolves completely after its effective operation. Implanted devices will provide a much better understanding of organ functions and offer more time efficient treatments for serious diseases such as heart failure.;Stretchable electronics can be achieved in two conceptually different, but complementary ways. One relies on the development of intrinsically stretchable, organic materials in conventional layouts, the other on mechanics-guided stretchable designs of inorganic materials. Many of the latter stretchable systems adopt an "island-bridge" design strategy, with the rigid active devices residing on the non-deformable platforms (i.e. islands), which are connected by the deformable interconnects (i.e. bridges). To ensure stretchable characteristic of electronics, the entire "island-bridge" structure needs to be integrated on soft, elastomeric substrates. The thesis first introduces the technology of transfer printing that allows brittle electronic systems fabricated on conventional substrate to be integrated onto target soft substrates of interest. Analytical models are developed to study the critical conditions for advanced techniques with high contrast modulation of adhesion suitable for transfer printing processes.;The second part of the thesis explores the material and composite substrate design for mechanically robust configuration of wearable tattoo electronics, with capabilities in multiple cycles of use in realistic settings. An analytical mechanics model for bilayer composite substrate design shows the effects from two layers can be decoupled in providing a robust, high strength system that maintains stretchable characteristics. The soft layer on top facilitates the stretchability of electronic systems and the relatively stiff layer at the bottom can significantly enhance their strength. In addition, the bottom substrate layer can be tailored to precisely match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering.;Lastly, the thesis presents a comprehensive set of materials and design strategies for transient electronic systems that offer stable operation followed by a complete dissolution in the human body and/or environment. The period of stable operation is defined by dissolution of encapsulation layers, whereas the functional degradation of the device system is defined by dissolution of either sensors or conductors. A model of reactive diffusion is established to understand the dissolution behaviors at both the material- and device-levels.
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