(729d) Liquid Metal Composites As Dielectric Materials for Extreme Conditions
AIChE Annual Meeting
2021
2021 Annual Meeting
Materials Engineering and Sciences Division
Multifunctional Composites for Thermal, Electronic, and Optical Applications
Wednesday, November 17, 2021 - 1:25pm to 1:40pm
Previous work has focused on achieving high performance at standard bench-top conditions. While these experiments are a good start with respect to proving the potential of LM/PDMS composites, they do not describe the full extent of conditions the composites are expected to be exposed to. For example, dielectric actuators and dielectric generators require materials with not only high permittivity but high dielectric breakdown as high voltages are typically necessary to achieve actuation. While PDMS, as well as other neat polymers, may have relatively high dielectric breakdown strength the methods that are typically used to improve conductivity or permittivity significantly degrade that breakdown strength. Capacitors, which are commonly the first point of breakdown in onboard electronics in rugged conditions, need to maintain their electrical performance at high temperatures and under mechanical impact. Traditional capacitor dielectric materials are either brittle (e.g., tantalum) or not thermally stable at high enough temperatures (e.g., thermoplastics).
In this work, we look at LM/PDMS composites, as well as model PDMS composite systems, under these extreme conditions, specifically high temperatures and high voltages, to understand what impact liquid metal has on the composite dielectric breakdown strength and permittivity. With the unique, metallic filler, it was expected that galinstan/PDMS composites would have some blend of previously described rigid filler and polymeric electrical behavior. It was found that dielectric breakdown strength was a function of galinstan concentration beyond a threshold concentration, which was an improvement upon the model conductive, rigid fillers. Multi-material composites were also studied to determine whether mixed conductive/capacitive rigid/deformable fillers could improve the dielectric breakdown strength of galinstan/PDMS composites without dramatically increasing the composite modulus. It was found that mixed composites of galinstan and conductive fillers showed an improvement in breakdown strength as compared to the single material composite of either while capacitive filler blends had a more complicated relationship. With respect to temperature, PDMS/galinstan composites were able to successfully maintain thermal, mechanical, and electrical integrity above 150oC (a temperature that most thermoplastic dielectrics cannot achieve), making them attractive to address defense and commercial shipping and infrastructure challenges.
The work presented demonstrates a significant jump forward in the real-world application of liquid metal/PDMS composites for use in sensors, actuators, and electrical systems. While soft and stretchable electronics are an exciting and dynamic area of research, work like this allows us to fully understand the capabilities of such materials to ensure reliability, durability, and high performance.