Microfabricated electrolysis pump system for isolating rare cells in blood

An integrated system for immunomagnetic separation of rare cells from blood is presented. A micromachined device was fabricated by bonding silicon die with etched structures to a glass cover plate on which electrodes are defined. Electrolytic generation of gas from 0.50 M KNO₃ (aqueous) provided pumping actuation for a device that performed the capture and purification of rare cells spiked into a 7.5 µl reconstituted blood sample. The system consisted of two pumps, a sample and a wash buffer meander reservoir, and a main channel for magnetic field trapping of rare cells captured by antibody-coated magnetic beads. A maximum pumping rate of 1.4 ± 0.1 µl min⁻¹ was obtained at a current of 180 µA, and the maximum blood sample volume delivered to the capture bed was 6.5–7 µl. The trapped cells could be washed with the buffer from the second pump and then delivered to the exit port of the chip after removing the magnetic field.