[nanoPost] Nano valves

Company USA

It consists of a membrane that deflects under pressure to pinch off the flow of fluids in a microchannel. The valve is made from two separate layers of elastomeric rubber which have been placed on a micro-machined mold such that grooved recesses are formed on one side of each layer. By bonding the layers together, the recesses form channels that crisscross in a solid structure.

The structure is sealed onto the top of a glass substrate. The surface of the substrate and the recesses of the bottom layer form the liquid "flow" channel. When pressurized gas is applied to the channels of the upper layer, the rubber deflects at precisely the intersection of the channels in the bottom layer. (See the animated tutorial.) This constitutes a simple, yet effective, valve.

In the 1970s engineers attempted to make microvalves using the semiconductor material silicon, but its rigidity made it impossible to fabricate structures that could regulate fluids at nanoliter volumes.

In comparison, elastomer is 1,000,000 times more flexible. The simple  valve has virtually unlimited potential for mixing and metering nanoliter volumes in a massively parallel fashion.

Benefits include the following:

Efficient use of sample and reagents. The valve creates virtually zero dead volume because it has no separate moving components. The channel itself closes, so switching one fluid for another requires very little in excess of what's needed for the biochemical reactions. This conserves sample and reagents and prevents cross contamination.
Small footprint. The ability to create extremely small valves means that integrated fluidic circuits can be designed that precisely control the metering and mixing functions and handle thousands of parallel reactions, in a miniaturized device. Because silicone is gas permeable, fluids can be blind filled into the IFC, and air bubbles escape naturally. This blind fill capability eliminates the need for a flow-through mechanism, which would add unnecessary bulk.

Parallel Processing Power. A network of  valves can be deployed as gates to compartmentalize aqueous solutions in up to hundreds of thousands of independent sample wells. Regardless of the complexity of fluid manipulations, the interface between the device and the external environment is simple and robust. Fluid is introduced into the IFC flow channels through steel pins inserted into the silicone. These inlets accept pressures of up to 300 kPa without leakage. The IFC can be designed to actuate some valves but not others by varying the width of the elastomer and adjusting actuation pressures.

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