Multilayer SU-8 based microdispenser for microarray assay

This paper reports on a microdispensing system for fast, stably and uniformly printing microarrays of DNA or protein on the nylon membrane for biological assay. This pneumatic actuation system is different from other common printing methods and adopts contact spotting technique instead of droplet injection. As a key component in the system, a microdispensing chip is successfully designed and fabricated by employing multilayer SU-8 spin-coating and photolithograph technologies, and the chip can simultaneously produce up to 25 individual fluid spots with the average diameters of 384 μm. A pressure of 10 kPa is optimal to dispense a 9:1 mixture of DMSO and percolated ink with the coefficient of variation (CV) of diameters as low as 2.6%, high stability and good reproducibility. A 3:7 mixture of DNA probe and DMSO can be perfectly printed on a 5 × 5 array by our microdispensing system as well as by a conventional computerized robotic system. Comparative study of two hybridized results has proved that our microdispenser is suitable and practical to produce moderate or low density microarray for biological assay.