A highly parallel picoliter dispenser with an integrated, novel capillary channel structure

Abstract

We present a cross-contamination free highly-parallel picoliter dispenser based on direct liquid displacement. Such dispensers are essential for the (mass) fabrication of microarrays [J. Ducrée, H. Gruhler, N. Hey, M. Mueller, S. Békési, M. Freygang, H. Sandmaier, R. Zengerle, TopSpot—a new method for the fabrication of microarrays, Tech. Digest, The Thirteenth IEEE Annual International Conference on Micro Electro Mechanical Systems, Mizyazaki, Japan, 23–27 January 2000, pp. 317–322] and are able to dispense up to 384 different reagents at a pitch of 500 μm simultaneously [A. Kuoni, M. Boillat, N.F. de Rooij, A highly parallel piezoelectric printing device for microarray technology, Tech. Digest, The 17th International Conference on Micro Electro Mechanical Systems, Maastricht, The Netherlands, 25–29 January 2004, pp. 466–469]. In contrast to an earlier design [Sens. Actuators A 103 (2003) 88] we investigated different nozzle diameters and a novel capillary channel design. We present a systematic study concerning the relation between nozzle diameter and ejected droplet volume. The change from 35 to 60 μm in nozzle diameter resulted in a doubling of dispensed volume for most used elastomers and irrespective of actuation parameters. Minimum and maximum dispensed volumes have been determined to be 125 and 1700 pl. Those results are based on a new design, which also includes passive microstructures for droplet homogeneity as well as modified microchannels for improved priming and prevention of cross-contamination. Based on this, the coefficient of variation (CV) of droplet velocity could be reduced from 50% down to less than 5%. The CV of droplet volume is clearly below the measurement error (8%).