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Wearables: Stretchable microstructures for microelectrode sensors

A unique method to make wearable electronics using flexible microstructures have been explored and characterized by researchers in the United States. Wearable devices such as sensors or power generators require stable, stretchable electronics, otherwise, their electrical performance will degrade when they are deformed. Prof. Swaminathan Rajaraman (Assistant Professor, MSE) and a team comprising of Ph.D. Student Charles Didier and Senior Post-Doctoral Fellow, Dr. Avra Kundu, both members of the Rajaraman Lab at the University of Central Florida investigated the capabilities and performance of 3D-printed microserpentines; shapes engineered to be flexible. They used an analytical model to optimize the design of the microserpentine structures to be maximally flexible. Next, they applied varying thicknesses of nano-gold to the microserpentines to determine which thickness remained most stable when stretched. Finally, the team incorporated the microserpentines into a sensor device to fabricate 3D microelectrodes and to take measurements from artificial skin. These findings demonstrate the potential of 3D-printed microserpentine structures for use in sensors and other wearable electronics.

The work was published in the prestigious Nature Microsystems and NanoEngineering journal on April 20, 2020. It is also the subject of a US Patent application.

Abstract of the paper:

We explore the capabilities and limitations of 3D printed microserpentines (µserpentines) and utilize these structures to develop dynamic 3D microelectrodes for potential applications in vitro, wearable, and implantable microelectrode arrays (MEAs). The device incorporates optimized 3D printed µserpentine designs with out-of-plane microelectrode structures, integrated on to a flexible Kapton® package with micromolded PDMS insulation. The flexibility of the optimized, printed µserpentine design was calculated through effective stiffness and effective strain equations, so as to allow for analysis of various designs for enhanced flexibility. The optimized, down selected µserpentine design, was further sputter coated with 7–70 nm-thick gold and the performance of these coatings was studied for maintenance of conductivity during uniaxial strain application. Bending/conforming analysis of the final devices (3D MEAs with a Kapton® package and PDMS insulation) were performed to qualitatively assess the robustness of the finished device toward dynamic MEA applications. 3D microelectrode impedance measurements varied from 4.2 to 5.2 kΩ during the bending process demonstrating a small change and an example application with an artificial agarose skin composite model to assess feasibility for basic transdermal electrical recording was further demonstrated.

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