Electrostatic Inkjet Patterning Using Si Needle Prepared by Anodization

A new electrostatic inkjet head composed of a Si needle having a very high aspect ratio was fabricated using a Si process combined with anodization, and fine droplets could be ejected with this head. An observation of droplet ejection with a high-speed optical camera revealed that ejection behavior can be categorized into two modes: a needle-mode ejection and an orifice-mode ejection. It was found that the mode of ejection could be determined by negative pressure applied to an ink reservoir. The mechanism of the occurrence of these two modes is discussed. The needle-mode ejection generated very fine droplets and a line of submicron width was drawn. These experimental results suggest that droplets whose size was less than a few hundreds nm were generated by the needle-mode ejection. The ejection of a photoresist material is also investigated.