Electrochemical detection of droplet contents in polystyrene microfluidic chip with integrated micro film electrodes

Detection of the droplet contents is a key function for droplet-based microfluidic systems. This paper presents a polystyrene microfluidic device integrated with droplet generator and micro film electrodes for direct amperometric detection of droplet contents without droplet desegmentation and phase separation. The method for fabrication of the full polystyrene micro chip was presented, and the behaviors of the developed polystyrene chip for generation and stabilization of water in n-octanol droplets, and detection of H2O2 in droplets were examined. The influences of electrode architecture and flow conditions on the electrochemical signals were studied in detail. With the developed chip, a sensitivity of 0.12 A mol−1 L cm−2 and a detection limit of 10.0 μmol L−1 were observed for the determination of droplet contained H2O2. The achieved precision for the detection of 21 droplets containing 250 μmol L−1 H2O2 was 3.8% in relative standard deviation. The way for the aqueous droplets encapsulated by the oil-carrier to contact sensing electrodes was discussed based on the experimental observations, and the potential approaches for further improving the analytical performance were suggested.