Characterization of simultaneous protein microarray formation by discrete micro stamper on surfaces of different wettabilities

Rapid and parallel protein micro/nano array formation provides a powerful tool for protein chip fabrication and protein preservation. This paper presents the characterization of surface tension and viscosity effect on the formation of nanoliter droplet array by a novel instant micro stamper, which can simultaneously immobilize hundreds of proteins on a chip. Besides, capillary force is the major driving mechanism of the micro stamper, flowing protein solutions through the chip channel for array-registration and droplet-size control. Three important properties have been characterized in this paper, including uniformity and repeatability of parallel printing process, surface wettability and solution viscosity effect on micro droplet size, and the dynamic sequence of micro droplet formation. First, experiment results demonstrated the uniformity and repeatability of the parallel stamping process for protein micro arrays from area to area and chip to chip. Second, the effects of surface wettability of bioassay chips and solution viscosity on droplet size variation have been investigated in detail by experiments and simulations. Both simulation and experiment results demonstrate that the spot size increases with the increasing of the surface wettability and the decreasing of the solution viscosity, and they showed similar tends. Furthermore, the dynamic process of droplet formation has been observed and analyzed by high-speed images, demonstrating that the foot print reduction rate, formation time, and necking of the printed micro droplet are lower on the more hydrophobic surface. This is due to the rapid shrinkage of droplet foot print area on hydrophobic surface, resulting in smaller droplet formation. As a result, the droplet size can shrink to 50% or 70%, when the contact angle of the bioassay chip surface increases from 30deg to 80deg, or solution viscosity varies from 1.02 to 10.08 cp, respectively