Impedance-activated microseparator based on amplitude modulation sensing and dielectrophoretic switching methods

We present an impedance-activated microseparator that can detect and isolate microparticles according to size. Using the amplitude modulation sensing method, the impedance-activated microseparator precisely detected the size of 5-, 8-, and 10-μm polystyrene beads. To obtain high sensitivity, sensing electrodes were designed in a parallel overlap electrode structure, including two excitation electrodes patterned on the roof and a sensing electrode patterned on the bottom floor. The peak output voltage was proportionally correlated with particle volume; thus, the measured peak output values were used both to calculate microparticle size and to count the number of microparticles. Experimental results showed that volume resolution of the impedance-activated microseparator is less than 30 μm3 and the minimum detectable particle size is approximately 2 μm in diameter. By using the dielectrophoresis-based track switching method, the proposed impedance-activated microseparator could isolate microparticles according to their size with greater than 90% separation efficiency. Consequently, the proposed impedance-activated microseparator may facilitate the identification and separation of microparticles according to size from a heterogeneous admixture.