Impedance spectroscopy for microfluidic particle-analyzing device with spatial-coplanar electrode design

In this work, we present a new microfluidic particle-analyzing device with a spatially coplanar-electrode design. To achieve effective particle analysis, 4 coplanar electrodes were designed and fabricated on glass substrates. Different from traditional cross-channel electrodes in impedance sensing, the coplanar design can be achieved without precise alignment issue, which is the major obstacle of traditional designs. Then, to characterize impedance spectroscopy of the device, a frequency spectrum of fabricated device impedance is employed. Based on the experimental results, theoretically simulated impedance behaviors are clearly compatible with experiments measured by fabricated devices. With different size of polystyrene beads (3, 6, 10 um) flowing through a set of 20um scale electrodes, we have experimentally demonstrated fabricated device's capabilities of differentiating bead sizes and positions due to resonance characteristics at the chosen frequency, 1 MHz. In addition, stray capacitance effect, well-known to deteriorate the detection of signals from bead flows, would be influenced and ameliorated by substrate material selection. This effect has also been discussed in this work on frequency analysis and simulation as well.