Reversing Elution Order in Insulator Based Dielectrophoretic Separations with Asymmetric Insulating Posts

An insulator-based dielectrophoresis (iDEP) separation of particles was developed where particles that experience strong DEP force (larger particles) were eluted first. This elution order is the opposite of existing iDEP separations. In this case, insulating posts were shaped asymmetrically; thus, particles experienced different net forces as they approached them from either side. Instead of a DC signal, a symmetric square waveform with a frequency of 0.4 Hz frequency and amplitudes ranging from 1400 V_PP to 2000 V_PP were applied. When the amplitude was such that a particle would be trapped when approaching the insulating posts from one side, but pass them when approaching them from the other side, that particle eluted. By increasing the amplitude in steps, large particles were eluted first, followed by smaller particles. This scheme is important for separations of larger cells, such as mammalian cells, which tend to lose viability rapidly during iDEP applications.