Single Cell Trapping by Superhydrophobic/Superhydrophilic Microarrays

Single cell trapping is demonstrated on superhydrophobic-superhydrophilic patterned microarrays. Superhydrophilic spots that are twice the size of the cells to be trapped are found to be optimal for obtaining single cell trapping. The single cell trapping is based on size exclusivity instead of heavy dilution of the cell suspension and relying on Poisson statistics. The superhydrophobic areas of the array are found to be very resistant toward unwanted adhesion of the cells and thus cleaning steps are not needed after deposition. Based on these properties, 20 mu m superhydrophilic spots are utilized for trapping two types of immune cells, primary peripheral blood mononuclear cells (PBMCs) and THP-1 cells. The cells are trapped from a 10 mu l cell suspension droplet dragged across the surface with different velocities. Single cell trapping efficiencies in the range of 10-30% are shown based on the cell type, the spot type, the seeding velocity and the cell suspension concentration.