Mobile micro screw pump with flow sensing capability for on-site flow control in microchannel device

This paper describes the development of a micro screw pump which can be installed anywhere where pumping is needed in a μ-TAS. We made this micro screw pump to let fluid flow at an extremely low flow rate with high response, and we also created a new method for on-site flow sensing by monitoring the position of the micro screw. The screw we use is made by microstereolithography with magnetically modified photo curable polymer previously reported in MEMS ´09. We placed the micro screw inside a glass capillary and rotated it by an external magnetic field at high frequencies. Because of the screw´s shape, it causes the surrounding fluid to be propelled forward. By decreasing the diameter of the tubing connected to the screw-housing capillary, we succeeded in producing extremely low flow rates. Since we use an electronic magnetic field to rotate the micro screw, we can realize a very high response when stopping the flow. We also pay attention to the position of screw which is influenced by three factors, the propulsive force, magnetic trap force, and static flow force, and we created a new method to monitor flow rate with knowing rotational frequency and position of screw.