Selective removal of contact printed nanowires for lithography-free patterning

Direct printing of inorganic nanowires (NWs) at selected locations on diverse substrates is an attractive route for obtaining multifunctional devices. Towards this, contact printing has been explored to assemble aligned NWs-based uniform electronic layers over large areas. However, repeated lithography steps are needed to obtain these electronic layers at selected locations, which is a cumbersome and wasteful process. Herein, we present a new method for lithography-free patterning of NW-based electronic layers at selected locations. First, contact printing is used to realise electronic layers of high-density, highly aligned NWs over large areas. Then, using a micropatterned elastomer stamp, we remove the NWs from locations where they are not required. To enhance the removal yield, we used the capillary-force-assisted stamp technique that uses a thin layer of evaporated water as an instant glue to increase the adhesion between NWs and elastomeric stamps. The optimised process shows a high removal yield (~99%), thanks to the strong capillary adhesive forces developed at the stamp-NW interface, and a good pattern fidelity. The present study demonstrates selective contact removal approach as a contamination-free NW patterning process suitable for large area, high-performance flexible electronics.