M-SWITCH™ Microfluidic bidirectional valve 

Many microfluidic applications require switching between multiple solutions (such as samples or buffers) while maintaining a constant flow rate during the associated experiment. In this application, one Flow EZ™ pressure channel is connected via a manifold to ten separate vials containing different aqueous solutions. Using the M-Switch™ and Oxygen software allows for selection of a specific solution to be directed to a microfluidic device. This represents an economical way to change between fluids, as it requires only a single pressure channel and one flow sensor. 

The microfluidic switching valve is first set to position 1, and a constant flow rate of 10µL/min is applied. A flow unit M coupled with a flowboard allows real-time monitoring of the flow rate for constant adjustment of the pressure. Then the M-switch position is changed to the next sequential position at several time points, and the measured flow-rate is recorded. 

The data for each switching interval was analyzed to determine the settling time for each change of position. Although it is possible to visually identify the switching step when reading the raw Oxygen data, in all cases normal flow was re-established within 100 ms or less. It is important to note that the flow rate is always positive during the switching steps, eliminating the possibility of cross-contamination between the various solutions. 

For more information, read our application note on this use of the microfluidic bidirectional valve.