Abstract
Rapid identification of microparticles in liquid is an important problem in environmental and biomedical applications such as microplastic detection in water sources and physiological fluids. Existing spectroscopic techniques are usually slow and not compatible with flow-through systems. Here we analyze single microparticles in the 10-24 μm range using a combination of two electronic sensors in the same microfluidic system: a microwave capacitive sensor and a resistive pulse sensor. Together, this integrated sensor system yields an electrical signature of the analyte particles for their differentiation. To simplify data analysis, 3D electrode arrangements were used instead of planar electrodes so that the generated signal is unaffected by the height of the particle in the microfluidic channel. With this platform, we were able to distinguish between polystyrene (PS) and polyethylene (PE) microparticles. We showcase the sensitivity and speed of this technique and discuss the implications for the future application of microwave cytometry technology in the environmental and biomedical fields.