Submicron microdevice patterning with plasma-thinned nail-polish microfiber shadow masks

Access to sub-micrometer electrode patterning remains limited in laboratories without lithographic or specialized mask-fabrication facilities. We present a novel, low-cost method for fabricating microdevices using nail-polish microfibers as shadow masks. A thin fiber is drawn by repeatedly touching a nail-polish droplet with a wire loop and placed directly onto the target substrate to define narrow features for metal deposition. As-drawn fibers reach diameters down to ∼2 µm and conform to both rigid and flexible surfaces. Oxygen-plasma thinning at ∼22 nm min^-1 reduces fibers initially ≥4 µm in diameter to below 1 µm, enabling electrode gaps down to ∼478 nm, as confirmed by atomic force microscopy. The process requires no spin-coated photoresist, baking, or development. Using this approach, we pattern microelectrodes on SiO₂/Si and polycarbonate and realize functional devices, including MoS₂ field-effect transistors, MoS₂ photodetectors, and a flexible device based on chemical vapor deposition-grown MoS₂. The method requires no photolithography, minimizes material cost, and leverages readily available tools and consumables, providing a practical route to prototyping and education as well as laboratory microfabrication.