Liquid loading of silicon-based cantilevers using electrowetting actuation for microspotting applications

An array of silicon-based cantilevers, so-called Bioplume, that can actively be loaded with liquid solutions was designed and fabricated for microspotting applications. Each cantilever incorporates a slit and a reservoir for liquid storage, and droplet formation occurs by a direct contact deposition technique. The loading scheme, based on the use of continuous electrowetting, was implemented either by patterning metallic electrodes inside the channel or by doping the silicon tip with phosphorus. Fabricated devices were tested using dimethyl sulfoxide (DMSO) and water–glycerol solutions. Application of a dc voltage between the liquid to be loaded and the conducting part of the cantilevers resulted in a liquid rise inside the channel. Voltages as low as 30 V were used to load the cantilevers and matrices of more than 50 droplets were successfully patterned with a single load. The diameter of achieved droplets ranged from 10 to 20 μm.