Injection and manipulation of silicon microbeads in a customized microfluidic platform

The first on-chip injection and manipulation of optically encoded, silicon microbeads in a microfluidic platform is reported. Encoded microbeads of different shapes and sizes were fabricated in silicon via standard microfabrication techniques. The optical signature consisted of a series of lithographically defined bar-codes, which can be identified by a laser detection system. In-situ identification of encoded microbeads was possible at microbead velocities ≤ 50 cm per second. The microbeads can also be transported within a channel network in accordance with the encoded optical signature of each bead. The microbead transport is controlled by the laminar flow of a liquid in pressure driven microchannels. Hydrodynamic pulsing facilitated single and multiple injection of microbeads from a reservoir into the laminar fluid stream of a branched microfluidic network. Careful control of the fluid velocity and alteration of the microchannel geometry also enabled manipulation of microbead velocity. The incorporation of five pillars to retain microbeads at a specific location within the microchannel network formed the basis of a reaction chamber for on chip functionalization of microbeads. The principle of hydrodynamic switching was utlized to re-direct the transport of microbeads at a branched microfluidic network. In the final part of this research we verify that this microbead technology is suitable for detection of specific target DNA.