Each slide rests on two O-rings that seal it to the vacuum manifold. An external vacuum source can be connected to the manifold with a manual valve that permits releasing the vacuum for removal of the slides. Low ridges position the slides laterally. The vacuum blast is of a greater flow than can be provided with a typical laboratory vacuum pump and is accomplished with a vacuum ballast tank which is constantly pumped by a normal pump and then released only during the dry cycle. A PC controls all of the other components and allows operator input of various parameters, such as number of probes, trays, and slides, spot spacing and pattern on the slides, durations of each cycle component and speeds and accelerations of the robot.
Humidity is controlled with a room humidifier controlled by an industrial humidstat.
The arrayer is able to put down 16 spots on each of 48 slides, and to wash and dry the probes for the next set of cDNAs for the next tray, in about 70 seconds. Most of this time is taken up with the actual spotting, as the wash and dry cycles are about 2 seconds each and the loading is about 10 seconds. Thus, the contents of one 96-well tray can be spotted every 7 minutes, and 10,000 spots would take about 12 hours. The reader designed at the the NIH is based on the original design by Brown and colleagues , although a number of additional features have been added in house. The reader is basically a computer-controlled inverted scanning fluorescent confocal microscope with a triple laser illumination system.