SU-8 nano-nozzle fabrication for electrohydrodynamic jet printing using UV photolithography

Efforts to directly printing nanoscale patterns by electrohydrodynamic jet for demanding device applications in electronics, medicine, and biotechnology have grown rapidly in recent years. However, printing of nano-patterns significantly depends on the fabrication of nanoscale nozzles. Here, we describe a low-cost and concise method for fabrication of SU-8 nano-nozzles only based on traditional UV photolithography. By this method, thermal and volume-shrinkage induced nanoscale crack can be automatically formed due to stress release after developing step. The influence of material, SU-8 layer thickness, and exposing duration on the stress in the SU-8 layer was analyzed to fabricate straight and long nano-crack. The result shows that the suitable material, SU-8 layer thickness, and exposing duration are silicon, 70 µm, and 46 s, respectively. Under the optimized condition, 60 µm long nano-crack with width of 250 nm and depth of 20 nm can be fabricated. The fluorescence image demonstrates the absence of blocking and leakage over the entire nano-crack.