METHOD FOR DEPOSITING A FLATTENED DROPLET ON A SURFACE AND APPARATUS THEREFOR, AND A PUMP THEREFOR

摘要

A method and apparatus therefor for depositing a flattened droplet on a partially absorbent surface comprising the steps of providing a narrow bore transfer tube having a proximal end and a distal end and containing a microvolume of liquid, the proximal end connected to a pneumatic system adapted for issuing an outgoing flow of displacement gas into the tube and drawing an incoming flow of displacement gas therefrom; and issuing an outgoing flow of displacement gas for slowly discharging substantially the entire microvolume of liquid as a droplet on the surface and controllably blowing one or more bubbles into the droplet towards the end of its discharg e for flattening the droplet on the surface. A pump (31) comprising a housing (33) having a bore (34) with an internal peripheral surface (36), and a stationary annular sealing member (48) integrally formed therewith at a firs t end (37) of a pair of opposite ends (37 and 38); a slide rod (39) disposed i n the bore and having an external peripheral surface (41) and a displaceable annular sealing member (49) integrally formed therewith; the sealing members sealing the peripheral surfaces to define a vented displacement volume (51) therebetween whose volume is proportional to an annular cross section area between the peripheral surfaces and a distance between the sealing members; and the slide rod being slidably reciprocable between first and second positions respectively toward and away from the stationary sealing member whereupon the displaceable sealing member moves to reduce the volume to issu e an outgoing flow of displacement gas from the displacement volume on a downstroke of the slide rod from its second position to its first position a nd the displaceable sealing member moves to increase the volume to draw an incoming flow of displacement gas into the displacement volume on an uspstro ke of the slide rod from its first position to its second position.