Liquid metal-based spatial-variant stretchable electronics via single-step programmable transfer printing

Despite tremendous advances in liquid metal (LM) patterning, as-fabricated LM-based patterns remain monofunctional as interconnects or sensors due to the predetermined, invariant electrical and electromechanical properties. System-level integration of functional units toward all-LM multifunctional stretchable electronics has been hindered by incompatible fabrication protocols or mechanical mismatch between units. This work introduces multifunctional all-LM stretchable electronics with spatial-variant electrical and electromechanical properties via programmable single-step transfer printing. Partial or complete transfer of LMPs via judicious engineering interface adhesion and LMP sizes leads to the transition of LM from the electrically conductive to nonconductive domain, along with tunability of their electrical resistance and electromechanical response. Spatial-variant LM patterns via single-step transfer printing can effectively avoid interfacial mechanical mismatch. Combining with compatibility for large-scale manufacturing, surface mounting, and skin interfacing, this single-step programmable transfer printing may pave the way for standalone all-LM stretchable electronics for physiological and mental health monitoring.