Impact of medium properties on droplet release in a highly parallel nanoliter dispenser

We report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies we found that for liquids of different viscosities the duration of the pressure pulse is the predominant effect compared to pressure amplitude. This result is of essential importance when actuation parameters have to be adopted for different media like oligonucleotides, DNA or protein solutions as it is the case for the non contact high throughput fabrication of microarrays [J. Ducree, H. Gruhler, N. Hey, M. Mueller, S. Bekesi, M. Freygang, H. Sandmaier, R. Zengerle, TopSpot-A new method for the fabrication of microarrays, Technical Digest, in: Proceedings of the Thirteenth IEEE Annual International Conference on Micro Electro Mechanical Systems, Mizyazaki, Japan, 23-27 January 2000, pp. 317-322]. For oligonucleotides printing we found coefficient of variations (CVs) of droplet diameter to be better than 1% within one single dispensing channel and 1.5% within all 24 channels for each used printing buffer. The CVs for protein printing were slightly higher but likewise for the oligonucleotides below 1%. Experiments with oligonucleotides as well as with different proteins showed ascertained carry-over and cross-talk free printing of DNA and protein microarrays. With it a prime critical point of microarray production is solved, leading to high quality whilst high throughput microarray fabrication. (C) 2004 Elsevier B.V. All rights reserved.