Assembly of polystyrene microspheres and its application in cell micropatterning.

Cell micropatterning has important applications in the development of biosensors and lab-on-a-chip devices, tissue engineering and fundamental cell biology studies. The conventional micropatterning techniques involve patterning of cells over a planar substrate. In this paper, we propose the introduction of topographical features on cell adhesive regions to enhance cell adhesion and function. The textured surface is created by assembly of polystyrene microspheres and the topographical parameters can be varied systematically by changing the size and density of the particles. A technique of generating spatial arrangement of microspheres on a non fouling background is developed. This is achieved by using a bi-functional template which has a patterned hydrophobic parylene film to facilitate self-assembly of particles; after assembly, the film is lift off, revealing a cell resistance background which is compatible with cell micropatterning. Particles were assembled by selective wetting of the hydrophobic-hydrophilic template. A fluidic chamber was designed to control the movement of the particle suspension across the template so as to attain uniform particle array over large area. This method of cell micropatterning can improve the efficiency and functionality of cell-based devices. It can also be used for examining the effects of topographical cues on cell-substrate adhesion which can provide valuable insights into cell biology and design of biomaterials.