A Closed-loop MEMS-based Spotter Integrating Position Sensors with Nanometric Precision for the Control of Droplet Uniformity

The reduction in dimensions of biochip arrays is of interest only if the size of the spots containing DNA or proteins is kept uniform. This condition is necessary to properly compare fluorescence signals from the different spots and thus to validate the results. Toward this aim, we propose a fully automated MEMS-based spotter enabling the spatial positioning of the depositing cantilever array and the control of the homogeneity of the printed droplets. This system relies on a closed-loop position monitoring of the microarray via integrated force sensing cantilevers. The fabrication of bioarrays can be performed automatically by this system without the need of an external optical setup but with the guarantee that the consistency of the droplet matrices is not affected by the sample topography. We have used this system to conduct preliminary studies on the influence of the contact time and force during deposition on the drop size according to the surface wettability.