Project

Liquid metal composite materials

Title: Bicontinuous morphologies of liquid metal – block copolymer blends for soft materials with enhanced conductivity and stretchability

Acronym: MetCopolPhases

Principal Investigator: Dr. Piotr Mocny

Location: University of Warsaw, Department of Chemistry, Biological and Chemical Research Center, Żwirki i Wigury 101, 02-089 Warsaw, Poland

Abstract:

Liquid metals (LM), such as eutectic gallium indium (EGaIn) have recently started to be used in the preparation of elastomer composites for both soft robotics and stretchable electronics. Metal fillers impart improved conductivity and may give a feedback signal upon material deformation, which is particularly useful for wearable sensors. In contrast to conventional solid fillers, liquid metals are soft and compliant, and thus mechanically compatible with human tissues. So far, liquid metal-composite materials have been prepared almost exclusively by simple mechanical blending of EGaIn with a host polymer of interest, usually commercial polyurethane (PU) or silicon-based elastomers. Another approach to prepare liquid metal-composites relies on surface-initiated radical polymerization, which, however, requires laborious steps and oxygen-free conditions. EGaIn can also be conveniently processed into nano/micro-droplets with the use of diblock copolymer surfactants, but their use in the preparation of liquid metal-composite materials has not yet been reported. Block copolymers with incompatible segments are known to microphase separate into diverse morphologies, such as lamellar of hexagonally packed structures. In principle, the same would be expected for their composites with liquid metals, in which the liquid metal can also serve as a matrix and not only as a filler. Thus, both can form a continuous phase, which may lead to dramatic improvements of thermal and electrical conductivities, as well as mechanical properties. This simple concept has surprisingly not yet been explored and it may lead to interesting morphologies and material properties.

This project will pursue the investigation of blends of EGaIn with block copolymers, more specifically, triblock copolymers and triblock molecular bottlebrushes comprising exterior binding segments that interact with the liquid metal droplets and serve not only as compatibilizers, but also as “glue” that provides mechanical integrity of the composite. The goal of the project is to obtain continuous morphologies of liquid metal – copolymer composites, i.e. with at least liquid metal phase being continuous for enhanced conductivities. Furthermore, liquid metals can be combined with small amounts of magnetic fillers to facilitate control over the self-assembly within these materials by poling with magnetic fields. In this manner, the continuous network of liquid metal may be easier to form. The liquid metal blends or composites are expected to be extrudable and reconfigurable, depending on the volume fractions of the components, and may potentially be applied in 4D printing approaches. Straightforward, one-step preparation processes are envisioned, which will rely on different blending approaches that include extrusion or sintering above the glass transition temperature, in the melt, or in the presence of plasticizers. The proposed materials are of fundamental scientific interest (specific aspects include morphology phase diagrams and structure-property relationships) and on account of their simplicity and the scalability of the production schemes and the anticipated properties that can be covered, they may also be technologically useful in soft robotics, for soft, wearable electronics as well as bioelectrodes.

This research is part of the project no. 2022/47/P/ST5/02945 co-funded by the National Science Centre and the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 945339.

 

See up-to-date publications

 

Published work preceding the MetCopolPhases research:

11. Herbert, R., Mocny, P., Zhao, Y., Lin, T. -C., Zhang, J., Vinciguerra, M., Surprenant, S., Chan, W. Y. D., Kumar, S., Bockstaller, M. R., Matyjaszewski, K., Majidi, C. “Thermo‐Mechanically Stable, Liquid Metal Embedded Soft Materials for High‐Temperature Applications“, Advanced Functional Materials, 2023, 2309725. https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202309725