Functional Composites That Contain Liquid Metal—Toward Soft Machines with Physical Intelligence

Soft machines will need to sense and respond to stimuli to be useful in unstructured environments and facilitate human-machine interactions. Soft materials that exhibit behaviors like stimuli responsivity will be critical to the function of these soft machines. The idea of physical intelligence highlights the ability of materials and machines to interact with their environment and demonstrate a wide diversity of behavior and should be a focus when developing new materials for soft machines. Composites that contain liquid metal are promising as functional materials that can facilitate physical intelligence, retaining deformability and compliance of the elastomeric matrix while also introducing metallic conductivity. Many reports describe composites that contain liquid metal and polysiloxanes, as these elastomers are commercially available and simple to prepare. While these composites offer utility for soft machines, further progress in the development of these materials will require matrix materials that introduce other functionality. In this talk, we’ll consider the synthesis and characterization of liquid metal composites that utilize functional matrix materials. For example, we used liquid crystal elastomers, which can change shape due to an applied stimulus. We fabricated a composite that could sense and respond to its environment, demonstrating of a primitive form of physical intelligence. The synthesis of this material relied on an understanding of the processing and assembly of liquid metal droplets. In developing this understanding, we extended our ability to process multifunctional composites by synthesizing liquid metal composites with a reprocessable plastic, a soft hydrogel, and a processable rubber for additive manufacturing. Our approach represents a widely applicable technique for creating new classes of multifunctional composites.