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Mechanics And Optimization Of Island-Bridge Structure With Serpentine Interconnects In Stretchable Electronics

Posted on:2016-02-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:H R FuFull Text:PDF
GTID:1228330467998231Subject:Structure engineering
Abstract/Summary:PDF Full Text Request
Stretchable/flexible electronics open up a range of important applications in the field of energy, medicine, biology and engineering science due to their abilities to allow extreme mechanical deformations. The island-bridge structures, as one of the stratagies to achieve stretchable mechanics for these devices, their mechanical behavior is a important subject concerning the design and application of the stretchable electronics. Focusing on the island-bridge structure, the research of this thesis includes following contents and conclusions:1.A theoretical model for the free-floating serpentine interconnect is developed, and the scaling laws for the critical buckling strain and elastic stretchability are established. The analytical solution demonstrates the relationship among the elastic stretchability, the serpentine interconnect and the cross-sectional aspect ratio, the unit cell number, the height/spacing ratio and the yield strain of the metal. Two buckling modes (i.e. symetric mode and anti-symetric mode) are identified and analyzed through combined experimental observations and numerical simulations, and the corresponding range of their geometric parameters are determined.2. The fractal-inspired design is illustrated, and an analytical model for the fractal interconnect is developed. The analytic solution of the elastic stretchability is obtained by establishing recursive formulate of thick interconnect flexibilities at different fractal order, and it demonstrates the relationship between elastic stretchability and the fractal order of the structure.3. A hierarchical computational model is proposed based on the mechanism of ordered unraveling for fractal-inspired thin interconnect. Compared with convertional finite element analyses (FEA), this approach save much computational effort and cost, but with accurate preditions, which is validated by experiments and FEA. Parametric study is conducted by applying this hierarchical computational model to postbuckling analysis of fractal interconnect, and the result demonstrates the relationship between the elastic stretchability and the fractal order, indicating the advantage of fractal design.4. Both experimental and theoretical studies are performed for the postbuckling analysis of fractal serpentine interconnects which are partially bonded to the substrate, and a scaling law of stretchability for this kind of interconnects is summarized. The solution demonstrates the relationship among the elastic stretchability, the unit cell number and the height/spacing ratio. 5. Experiment and numerical simulation are performed for a stretchable copper electrode, and the results indicate that the serpentine interconnect which is outperforming the design of island-bridge structure with straight interconnect. Based on the theoretical model developed in the previous sections, the process for design optimizaton of fractal interconnects is illustrated, and the optimization results indicate that the fractal interconnects can achieve a larger elastic stretchability than the serpentine interconnect. A epidermal health monitor is carried out by exploiting the island-bridge structre with fractal interconnects, which can laminate onto the skin to acquire electrophysiological data from human bodies.In summary, this thesis present a systematic study of mechanical behavior for island-bridge structure with serpentine interconnect, through combined experimental observations, analytical modeling and numerical simulations, and achieve innovative result on theoretical model, computational approach and optimization method of serpentine interconnect and fratcal interconnect.
Keywords/Search Tags:stretchable/flexible electronics, serpentine interconnect, mechanical properties, fractal, postbuckling
PDF Full Text Request
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