A Portable Capacitively Coupled Contactless Conductivity Detector Based on ARM9 Microprocessor

Abstract

A portable capacitively coupled contactless conductivity detector for microfluidic chips was presented.The detector was based on the ARM9 embedded platform,and all functions of the detector were controlled by an ARM9 microprocessor.The hardware of the detector included a signal excitation unit,a signal conditioning unit,a data acquisition unit,a data processing unit and a touchscreen.The software of the detector consisted of an operating system,hardware drivers and application programs.The range of the excitation frequency of the detector was 0-2 MHz,and the range of the excitation voltage was 0-20 V(peak to peak,Vp-p).The dimensions of the detector were 130 mm×102 mm×35 mm.With the detector,the sensitivity of a three-layer microfluidic chip was tested.The chip was composed of a poly(methyl methacrylate) electrode plate(containing Cu detection electrodes),a 16 μm-thick polydimethylsiloxane(PDMS) insulating layer and a PDMS channel plate(containing the microchannel).The solution was driven into the microchannel from the tip of the chip by a peristaltic pump,and detected at the electrode cell.A limit of detection of 9.1 μmol/L for potassium chloride was obtained at the optimal excitation frequency of 50 kHz and voltage of 20 Vp-p.