Self-Aligned Fabrication and Contact Line Pinning Characterization of Pedestal Nozzles

Silicon dioxide pedestal nozzles are introduced, featuring a sharp concentric rim with an edge angle of approximately 5° and a sub-20 nm radius of curvature. The nozzles show an unprecedented ability to pin the contact line of de-ionized water, and apparent contact angles exceeding 210° were observed. A dynamic contact angle characterization method is introduced to determine the pinning capabilities of the nozzle. The nozzle is vibrated with a piezo actuator and brings pendant droplets close to their resonance frequency. Larger contact angles are observed for smaller droplets, because they can be driven closer to the resonance frequency before pinch-off.