Fabrication and Characterization of Multifunctional Soft Composites for Hybrid Electronic Systems

There has been an ever-increasing need for soft, functional materials within areas of research such as soft robotics, flexible electronics, and wearable devices. These materials must be stretchable and/or flexible, thermally and electrically conductive, and robustly adhesive to a wide variety of substrates and surfaces. Over the past several decades, soft composites consisting of functional solid particles within an elastic matrix have been developed with the aim of achieving these properties. However, solid particulate fillers in elastomeric materials have various limitations which hinders the ability to achieve the aforementioned properties simultaneously. In this work, two novel approaches to developing soft conductive adhesives are introduced in an effort to solve mechanical, thermal, electrical, and adhesive trade-offs. The composites developed herein utilize liquid metal (LM) inclusions and a combination of LM with solid silver (Ag) flakes within deformable polymer matrices to maintain mechanical compliance while also achieving thermal and electrical functionality. Furthermore, adhesive properties of LM composites are enhanced through a chemical anchoring technique, while the composition and microstructure of LM-Ag composites are designed to control functional and adhesive properties. There are several demonstrations throughout which show the ability to robustly integrate the novel soft composites with rigid materials and electronic components for the creation of resilient and functional hybrid electronic systems.