Position-independent microparticle sensing: microwave sensors integrated with metalized, 3D microelectrodes

Abstract

Microfluidics integrated microwave sensors can be used for high throughput and label-free sensing with single particle resolution. For microwave sensors with coplanar electrodes, electric field is nonuniform over the height of microfluidic channel, causing position dependent sensitivity. One way to resolve positional dependency is to place electrodes on the sidewalls of microfluidic channel to obtain uniform electric field. Here, we demonstrate a novel, metal coated 3D SU8 microelectrode integrated with microwave resonator to obtain uniform electric field inside microfluidic channel and mitigate position dependent sensitivity. SU8 electrodes are positioned at the sensing region of the resonator, in contact with the microfluidic channel walls. During microparticle sensing experiments, phase and amplitude of the resonator are tracked using custom built single side band detection circuitry to detect particle induced shifts in these signals. Results of particle sensing, and size classification experiments indicate that with 3D SU8 electrode integrated microwave resonators, position-independent sensitivity can be achieved.