Apparatus for dispensing a predetermined volume of a liquid

This invention relates to apparatus for dispensing a predetermined volume of a liquid, comprising a source or reservoir for the liquid, a channel provided with an outlet for conveying the liquid from the source or reservoir to the outlet, and means for generating pulse of gas, the apparatus being constructed and arranged such that in use said pulse of gas causes a predetermined volume of liquid to be ejected from said outlet. It relates particularly, though not exclusively, to apparatus for dispensing biochemical reagents. Dispensers for dispensing biochemical reagents can provide a non-contact means for dispensing small volumes of a liquid, commonly in the range 0.1 nl to 100 l. Dispensers based on conventional ink jet printer technologies are most generally applied for dispensing volumes in the 0.5 nl to 10 nl range. Apparatus for dispensing a predetermined volume of a liquid () comprises a reservoir () for the liquid, a channel () provided with an outlet () for conveying the liquid () from the reservoir to the outlet, and means for generating a pulse of gas. The apparatus is arranged such that the flow of gas causes a predetermined volume of liquid to be ejected from the outlet. The outlet comprises a pair of openings in the channel which face one another, the liquid being retained between the openings by surface tension in the absence of a flow of gas. The gas flow is directed towards one of said openings in use. The apparatus may be used to dispense volumes of a liquid reagent in the range 1 nl to 2 l. The apparatus avoids contamination of the liquid, and dispensing head construction allows devices to be low cost disposable units. The apparatus is less sensitive to liquid viscosity than existing devices.