Reconfigurable electronic devices enabled by laser-sintered liquid metal nanoparticles

Liquid metals are promising conductive materials for creating flexible and stretchable electronic devices. However, methods to pattern liquid metal remain limited in scope: fabrication processes often require substantial manual intervention and the resulting devices are often patterned indelibly into the substrate. In this paper, we demonstrate the creation of electrical traces and components from laser-sintered liquid metal nanoparticles, a digital fabrication approach that creates devices without permanently patterning the materials. As deposited, the liquid metal nanoparticles form a non-conductive film because the conductive liquid metal cores of each particle are surrounded by a non-conductive metal oxide shell. Conductive traces are patterned into the film using an infrared laser to sinter and coalesce the nanoparticles. We demonstrate that we can create resistive and capacitive electrical elements by tailoring the geometry of the laser-sintered patterns. Furthermore, the patterned capacitors can be used to sense the proximity of an object and the patterned resistors can be used in conjunction with analog integrated circuit components to create analog circuits. We show that the fabricated analog circuits can be reconfigured and reused to attain different output responses. The laser processing technique also offers the opportunity to create stretchable conductive traces. We show that compound laser processing can be used to both sinter the nanoparticle film and cut the underlying substrate in the same processing area to achieve in-plane stretching via out-of-plane flexing of liquid metal films.