Transient Bioelectronics: Electronic Properties of Silver Microparticle- Based Circuits on Polymeric Substrates Subjected to Mechanical Load Reihaneh Jamshidi, Simge C¸inar, Yuanfen Chen, Nastaran Hashemi, Reza Montazami Department of Mechanical Engineering, Iowa State University, Ames, Iowa, 50011 Correspondence to: R. Montazami; (E - mail: reza@iastate.edu) published online 00 Month 2015 DOI: 10.1002/polb.23804 ABSTRACT: Transient soft bioelectronics are capable of forming conformal contacts with curvilinear surfaces of biological host tissues and organs. Such systems are often subject to continu- ous static and dynamic loads from the biological host. In this article, we present investigation of electronic attributes of tran- sient soft bioelectronic circuits subjected to mechanical force and influence of substrate’s transiency on the transiency of the whole device; also, characterize and quantify loss of functional- ity in triggered devices. Variations in the electrical conductivity of circuits as a function of applied mechanical load was used as a means to deduce electronic characteristics under stress. The experimental results suggest that there exists a correlation between electronic properties of circuits and applied mechani- cal strain; no clear correlation was, however, observed between electronic properties of circuits and frequency of the applied dynamic load. Control over transiency rate of identical circuits utilizing the transiency characteristics of the poly(vinyl alcohol)l-based substrates is also studied and demonstrated. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 00, 000–000 KEYWORDS: bioelectronics; biomaterials; degradation; func- tional polymers; mechanics of soft electronics; structure- property relations biodegradable; transient electronics; tran- sient polymers INTRODUCTION Recent advances on integration of electric circuits on advanced soft materials have enabled an emerg- ing field at the junction of materials science, electronics, and biology. Bioelectronics, due to their unique characteristics, such as biocompatibility and flexibility, allow direct integra- tion of electronic devices on curvilinear biological tissues. 1–5 Thus far, there has been significant improvement on active (e.g., pacemakers), and passive (e.g., artificial hips and joints) nondegradable biomedical components, as well as passive (e.g., sutures) bioresorbable biomedical components. How- ever, active bioresorbable components (bioelectronics) is still an immature field of study with great potentials and oppor- tunities. Recently, integration of biodegradable organic and inorganic electronics on transient substrates has enabled the development of transient bioelectronics. Transient electron- ics, in general, is an emerging field in materials science and engineering focused on materials and structures that can maintain full functionality up to the point they are no longer needed, and undergo fast self-destruction when transiency is triggered. Trigger and triggering mechanisms vary from heat/melting 6 to solvent/dissolution 7,8 to light/photodecom- position, 9 to name few examples. Transient bioelectronics with controlled transiency rate are realized by fabrication of circuits and electronic components of organic and inorganic biodegradable materials 8,10–13 on substrates with controlled transiency rate 14,15 ; and can limit or completely eliminate the need for secondary invasive surgeries required to remove implanted bioelectronics, once the operation period is com- pleted. 7 Controlling transiency rate of electronic components of transient bioelectronics is very often more challenging than that of transient substrates because the electronic properties of electronic components may be compromised for transiency attributes, which is overall undesirable. Early works on transient materials and electronics started with electronics on bioresorbable substrates and also partially transient electronics with certain degradable components. Instances of the first studies include conformal bioelectronics based on bioresorbable silk substrate in which dissolution of silk initiates wrapping of electronics around biological tis- sues. 16,17 Instances of partially dissolvable electronics include devices in which all components except electrodes and inter- connects are dissolvable in biological medium. 12,15 Recently, fully dissolvable electronics have been reported by Rogers et al. They use silicon as the semiconductor, metal oxides (MgO, SiO 2 ) as dielectrics, Mg for conductors and silk as the substrate and packaging material. 7,8 Another example of a fully transient electronic is a RF pressure sensor which uses a Zn/Fe bilayer as the sensor conductor material, poly-L-lactide as dielectric and polycaprolactone as the structural material. 18 More recently high performance transient electronics, 11 V C 2015 Wiley Periodicals, Inc. 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