Michael Dickey1

1, North Carolina State University, Raleigh, North Carolina, United States

This talk will discuss methods to directly print liquid metal alloys into 3D structures at room temperature and embed it in functional polymers to create conductors that are soft, self-healing, and ultra-stretchable. The metal is a gallium-based metal alloy that is a low-viscosity liquid at room temperature with low toxicity and negligible vapor pressure. Despite the large surface tension of the metal, it can be printed into non-spherical shapes due to the presence of an ultra-thin surface oxide skin. We have harnessed these properties to form a number of electronic devices encased in polymer matrices. For example, the metal can be printed to create stretchable interconnects between rigid thermoelectric ‘legs’ encased in elastomer; the resulting device is flexible and can be used in wearable devices to convert body heat into electricity. We have also utilized the ability to withdraw the metal from 3D printed structures as a sacrificial, fugitive ink to create microvasculature in polymer monoliths. The talk will discuss these examples as well as the key parameters that make printing possible. We found that the gap between the nozzle and substrate is important since printing is shear-driven. The ability to print metals at room temperatures is promising because it can enable co-printing of metal with temperature sensitive materials such as polymers, elastomers, and biological materials.