Microfluidic method for in-situ deposition and precision patterning of thin-film metals on curved surfaces

We present a technique for patterning thin-film metals (silver and gold) without the need for photolithography. The technique involves microfluidics and can be performed on planar or curved surfaces. Patterns of thin-film metal are fabricated by flowing electroless silver or gold plating solutions through predefined microchannels made of polydimethylsiloxane sealed against a surface of interest. We demonstrate metal resistors with 100-μm-wide traces fabricated on planar and curved surfaces. The surface profile, mechanical gauge factor, and temperature coefficient of resistance have been characterized. Application of the resistors as hot-wire flow sensors has also been demonstrated.