Liquid droplet dispensing

A dispensing assembly for liquid droplets of the order of 30 μl or less in volume comprising:

• a pressurised liquid delivery source;
• a metering valve body connected to the liquid delivery source, the body comprising an elongated body member having an internal main bore and a base forming an apertured valve seat;
• a valve boss in the bore, the cross-sectional area of the valve boss being sufficiently less than that of the main bore to permit the free passage of liquid therebetween;
• a nozzle mounted on the base of the body member comprising a dispensing tip and having a nozzle bore communicating between the valve seat and the dispensing tip;
• a variable power output valve boss actuator for moving the valve boss in the bore between a closed position engaging the valve seat and an open position spaced-apart from the valve seat;
• a valve boss detector for determining the movement of the valve boss within the bore;
• and
• a controller connected to the valve boss detector and to the valve boss actuator for varying the power input to the valve boss actuator depending on the movement of the valve boss within the bore.