Low Cost Electrodes Cell in Capacitively Coupled Contactless Conductivity Detector for microfluidic Chemical Analysis

In this paper, a low cost electrodes cell for capacitively coupled contactless conductivity detector (C4 D) is studied. The electrodes cells were fabricated by printed circus board (PCB) photolithography, and coupled with polydimethylsiloxane (PDMS) microchips. Potassium (K⁺) and sodium (Na⁺) were separated and detected in this system. Experiments were carried out based on different parameters and designs. Parameters including frequency (75, 150, and 300 kHz), voltage (-12 and -6 dB of full output voltage), gain (50%, 75% and 100%), ADC (16.66, 19.80 and 34.15 Hz), and filter (medium, fast and off) were set up on the detector before each run. Electrodes width was tested using PCB electrodes cells with 0.7 and 1 mm widths. Microchip channel length was tested with 35 and 40 mm channels. These lengths were achieved by moving the microchip on top of the electrodes cell. Microchip channel width was tested using microchips with 100, 75 and 50 μ m width channels. The electrodes cells performed very robust detection ability, with flat and stable baseline, and satisfied signal-to-noise ratio (SNR).