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Integrated micro-biosensors and microfluidic systems have been recently used for detection of cells, proteins, and other biomarkers for a wide range of applications. In this work, open micro-channel flows driven by capillary force designed for food safety applications are studied. The micro-channels are used to deliver the nutrients (extracts of different fresh produce) to the sensing site where pathogens reside. The presence of nutrients, simulating the condition that micro-organisms experience in real food materials, allow us to investigate their behavior in real time. Open channels studied in this work are partially covered to allow for etching of the sacrificial layer that creates the channel and use of capillary force to create a self-driven microfluidic system in which fluid flow is actuated by surface tension and wall adhesion. Numerical simulations are used to investigate the fluid flow regime in micro-channels using ANSYS FLUENT. The volume of fraction (VOF) method is used to simulate the dynamics of fluid flow in microchannels made of polycrystalline silicon with a thin layer coating of native silicon dioxide. The effects of channel size and different geometries (open channel, T-junction, and L-junction) on a flow rate of water in the channel are investigated. Our study shows that adding T- and L-junctions to the flow path would create a small delay in the fluid flow in the channel, and the number of junctions directly affect the delay, however, it does not prevent the fluid transfer by capillary force. The (partially covered) open channel geometry presented in this work is compatible with conventional surface micromachining process. |
