Rapid Prototyping for Soft‐Matter Electronics

A series of rapid and inexpensive methods to produce elastically soft sensors and circuits in minutes using a CO₂ laser (10.6 μm wavelength) are introduced. These soft‐matter electronics are composed of laser‐patterned films of conductive poly(dimethylsiloxane) (cPDMS) and liquid‐phase gallium–indium (GaIn) alloy embedded in a thin sheet of soft silicone elastomer. Direct laser patterning eliminates the need for photolithography, replica molding, and customized inkjet or microcontact (μCP) printing, and allows conductive traces of cPDMS and liquid GaIn to be rapidly integrated into a single soft‐matter circuit. The versatility of this fabrication method is demonstrated by the production of a variety of electrically functional soft‐matter sensors and circuit elements that contain features with >150 μm planar dimensions. It is postulate that in the case of GaIn alloy patterning occurs when the recoil force of the escaping vapor exceeds the liquid's surface tension. This mechanism exploits the unique “moldability” of liquid GaIn alloy, which forms a surface oxide of Ga₂O₃ that allows the patterned film to maintain its shape.