Direct on-device synthesis of Au micro/nanowires via open microfluidics for integrated temperature sensing

Temperature sensors are widely used across electronics, healthcare, and industrial systems. Among the various device architectures, micro- and nanowire-based temperature sensors have emerged as attractive candidates because their high surface-to-volume ratio and confined charge transport pathways enable improved sensitivity and spatial resolution. However, their practical implementation remains limited by complex post-processing steps, including wire transfer, alignment, and integration. Here, we introduce an open microfluidic fabrication strategy that unifies localized synthesis, direct patterning, and on-device integration of Au micro/nanowires. By spatially confining reactive laminar streams in open fluidic space, Au wires with dimensions spanning the nano- to microscale can be continuously synthesized and directly patterned onto device substrates without additional transfer or alignment processes. As a proof-of-concept demonstration, the directly fabricated Au wires were employed as resistive temperature sensors, exhibiting linear responses over 25-50 °C, with a resistance change of 6.25 Ω °C^-1 and a temperature resolution of 0.32 °C. Sensors with different wire widths reveal that thinner wires show higher intrinsic resistance and stronger temperature-dependent modulation of electron transport. This work establishes a simple, flexible route for integrated micro/nanowire device fabrication and highlights the potential of open microfluidics as a scalable platform for constructing miniaturized sensing systems.