Micro gap measurement by vibration mode for needle-type dispenser

A needle-type dispenser, consists of a thin needle and a glass capillary, has been developed for micro-droplet application from high viscosity liquids. A gap, which is a distance between the needle tip and the target surface, is formed in micro-droplet. If the gap is fluctuated, volumes of applied micro droplets are unstable. Therefore, a contact-detection method of the needle-tip droplet and the target surface is proposed. The needle is vibrated by the piezoelectric element through the leaf spring in the proposed method. Contact of the needle-tip droplet and the target surface can be detected from needle-vibration characteristics. In this paper, control of the gap and droplet volume using needle-vibration characteristics is reported.