Hydrogen and calcium ion electrochemical detecting systems using microfluidic technology

A microfluidic chip capable of monitoring the concentrations of hydrogen ions and calcium ions in an automatic format is presented. The microfluidic chip is composed of two modules, namely a fluidic control module and a sensing module. The fluid control module comprising a micro-pump, two micro-valves and microchannels can automatically transport samples to the detection zone. The sensing module located in the detection zone is composed of two electrochemical sensors for detecting pH value and calcium ions, temperature sensors and a flowrate sensor. Platinum electrodes with a sputtered SLBTLO (SiO2-LiO2-BaO-TiO2-La2O3) film and an ion-selective membrane are used as pH and calcium ion sensing electrodes, respectively. The potential differences between the sensing electrodes and reference electrodes indicate the hydrogen and calcium ion concentrations of the samples. The built-in flowrate sensor can continuously monitor the flowrate generated by the micro-pump. As the voltage potential signals of these two ions can be significantly affected by the environmental temperature, the built-in temperature sensor provides the compensation information. Experimental data shows that the developed microfluidic system can successfully detect the pH value and the presence of calcium ions simultaneously. The volumes of the sample required were reduced to 70 µl, which is much less than the volumes required for the traditional method (about 30 ml). When compared with large-scale sensing systems, the microfluidic chips could sense multiple ion concentrations simultaneously and have a comparable sensitivity, with a quicker response. The multi-functional electrochemical chip can be a useful tool to continuously detect multiple ions for biomedical and industrial applications.