If higher quality DNA microarrays could be fabricated at a much faster rate and at significantly lower cost, then new applications such as the measurement of real time gene expression might become feasible. Many microarrays are currently printed with steel pins that are made manually in a machine shop and sell for up to $625/pin. We propose to design and fabricate, using standard micromachining procedures, a monolithic micromachined silicon printhead which should be capable of printing hundred or even thousands of DNA spot samples simultaneously. The first generation design will include an integral 0.5-1.0 uL reservoir for the printing fluid and print elements with tip diameters selectable from 20-75 um each of which is individually spring loaded to compensate for local height variations in the printing surface. The first prototype designs will incorporate 75 um print tips in either a 10 x 10 = 100 array of tips on 2.25 mm centers (1536 microtiter plate format) or a 20 x 20 = 400 on 1.125 mm centers (6144 format). This technology should be easily adaptable to current high throughput protocols and allow microarray users to rapidly benefit from the high precision, economy of scale and increased throughput derived from the parallel silicon micromachining and fabrication.
