Collaborative Research: Identifying the Dielectric Properties of Liquid-Metal Polymer Composites to Ensure the Dielectric Integrity of Deformable Electronic Applications

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Nontechnical SummaryBioelectronics and soft robotics require electronic materials that function while being stretched or compressed. Composites of soft polymers with metals that are liquid at, or near, room temperature, have recently gained extensive attention from the scientific community for such applications. They have shown impressive performance as stretchable electronic components and for physiological sensors. Prior research has focused on expanding the promise of these composite materials, but relatively little has been done to understand their electrical aging and failure mechanisms. The lack of knowledge could lead to premature failure and may put future technologies utilizing liquid metal polymer composites at risk. This project combines experimental analysis and numerical modeling to identify the key characteristics that lead to the unique electrical performance and breakdown of liquid metal polymer composites. With the understanding established through this project, future soft electronic technologies can be developed with application-specific performance and long-term durability in mind. The novel findings of this project will be utilized to promote underrepresented minority student intertest in STEM. Building on the existing relationship with the Girl Scouts and by taking advantage of the world-class high-voltage lab, a series of polymer, capacitor, and high voltage-related experiments will be designed for young women and K-12 students. Furthermore, short courses on high-voltage engineering and dielectrics with use cases on deformable dielectrics will be delivered at community colleges to promote university recruitment in Alabama and Mississippi. This project is jointly funded by the Electronic and Photonic Materials (EPM) program of the Division of Materials Research (DMR), the Established Program to Stimulate Competitive Research (EPSCoR), and the Metals and Metallic Nanostructures (MMN) program of DMR. Technical SummaryLiquid metal polymer composites (LMPCs) have shown impressive performance by simultaneously providing high dielectric permittivity and low modulus. While previous research has demonstrated that the composite formulation can be tuned to address the specific needs of soft capacitor and tensile or pressure sensors, little work has focused on the long-term effects of using LMPCs as dielectrics. Specifically, the dielectric aging and failure mechanisms of LMPCs that vary by application-specific electrical stresses are currently unknown. The goal of this project is taking an integrated experimental and modeling approach to develop a first principles understanding of the key parameters governing the dielectric performance and aging mechanism of LMPCs. The team will investigate the effects of droplet shape, size, loading, composition, mechanical loading, and voltage stress type on the permittivity, dissipation factor, partial discharge inception voltage, and dielectric strength of LMPCs. A finite element analysis simulation environment will be used to model trends in permittivity and variation of the dielectric strength. The outcomes of this project will enable future deformable technologies that take advantage of LMPCs to not only tailor formulations to a specific application, but also maximize device lifetime and dielectric integrity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.