Date of this Version
Haake, A., Tutika, R., Schloer, G.M., Bartlett, M.D., Markvicka, E.J. 2022. On Demand Programming of Liquid Metal-Composite Microstructures through Direct Ink Write 3D Printing. Undergraduate Honors Thesis. University of Nebraska-Lincoln.
Soft, elastically deformable composites with liquid metal (LM) droplets can enable new generations of soft electronics, robotics, and reconfigurable structures. However, techniques to control local composite microstructure, which ultimately governs material properties and performance, is lacking. Here we develop a direct ink writing technique to program LM microstructure (i.e., shape and orientation) on demand throughout elastomer composites. In contrast to inks with rigid particles that have fixed shape and size, we show that emulsion inks with LM fillers enable in-situ control of microstructure. This enables filaments, films, and 3D structures with unique LM microstructures that are generated on demand and locked in during printing. This includes smooth and discrete transitions from spherical to needle-like droplets, curvilinear microstructures, and geometrically complex embedded inclusion patterns. The printed materials are soft (modulus < 200 kPa) and highly deformable (> 600% strain). We demonstrate these capabilities by embedding elongated LM droplets in a soft heat sink, which rapidly dissipates heat from high power LEDs. These programmable microstructures can enable new composite paradigms for emerging technologies that demand mechanical compliance with multifunctional response.