Omnidirectional printing of elastic conductors for three-dimensional stretchable electronics

초록

Three-dimensional printing could be used to create complex and multifunctional soft electronic devices. However, printing solid-state elastic conductors with three-dimensional geometries is challenging because the rheological properties of existing inks typically only allow for layer-wise deposition. Here we show that an emulsion system-consisting of a conductive elastomer composite, immiscible solvent and emulsifying solvent-can be used for the omnidirectional printing of elastic conductors. The viscoelastic properties of the composite provide structural integrity to the printed features-allowing freestanding, filamentary and out-of-plane three-dimensional geometries to be directly written-and pseudo-plastic and lubrication behaviours that provide printing stability and prevent nozzle clogging. Printed structures of the intrinsically stretchable conductor exhibit a minimum feature size less than 100 mu m and stretchability of more than 150%. The vapourisation of the dispersed solvent phase in the emulsion results in the formation of microstructured, surface-localized conductive networks, which improve the electrical conductivity. To illustrate the capabilities of our approach, we create a skin-mountable temperature sensor with a matrix-type stretchable display based on omnidirectionally printed elastic interconnects. Freestanding, out-of-plane structures made of stretchable conductors can be printed using an emulsion-based ink that has the viscoelasticity to be extruded into three-dimensional geometries and supporting its own shape.

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