On-demand droplet spotter for preparing pico- to femtoliter droplets on surfaces

A droplet spotter for on-demand generation of pico- to femtoliter droplets was developed to meet the requirement for high-density spotting of chemicals on a surface, Our droplet spotter involves applying a similar to 1000-V and similar to 10ms pulse voltage to the tip of a capillary tube (o.d. similar to 18 mum; i.d. similar to 11 pm) supplied with water or a dye solution. The capability of the spotter was demonstrated by preparing a microarray of dye molecules. The microarray was prepared by spotting similar to 30-fL droplets of a dye solution on a surface at the density of one spot per 20 x 20 mum(2).