A spiral channel with integrated microelectrodes for label-free particle lateral position and size characterization

Modified-trident shaped microelectrodes were incorporated into a spiral-shaped microfluidic focusing channel, utilizing impedance flow cytometry to analyze and quantify inertial microfluidic-based separation of homogeneous particles differing in size. Double peak voltage pulses were generated as particles moved across the electrodes, where the ratio of the peak amplitudes indicated the lateral particle positions inside the channel at various flow rates, while the peak amplitude indicated particle size and vertical position. The root mean square error between the optical and electrical position measurements was 11.44 µm reflecting the lateral position measurement resolution. The peak amplitudes were used to estimate particle size after being adjusted to account for particle vertical position using a shape parameter, which effectively reduced errors in particle size calculations. The particle size estimate sensitivity was measured to be 2.15 μm/mV from the peak amplitudes. The electrodes with the appropriate signal processing were able to detect both the size and location of particles after separation with a spiral channel, showing their utility in potentially controlling the separation conditions for these devices.