Smart phone-powered capillary electrophoresis on a chip for foodborne bacteria detection

Due to the requirement of high-voltage power supply, on-chip micro-capillary electrophoresis (mu CE) suffers from practical on-site bioapplications. In this paper, we introduced a smart phone based electric power system for mu CE on a chip with simple electrical operations and improved portability of a mu CE device. Since the power of the smart phone is limited to 5 V, we utilized a boost converter circuit to increase up to 250 V, which enables mu CE on a chip. The typical CE channel with a cross design was patterned on the PMMA substrate, and the sample, the waste, the anode and the cathode reservoirs were fabricated. Two steps of mu CE consisting of the injection and the separation were performed to separate two amplicons (121 bp FliC gene of Escherichia coli and 161 bp InvA gene of Salmonella serovar Typhitmrium). During the injection step, the voltages applied in the sample and waste reservoirs were 0 V and 250 V, respectively, and the amplicons were filled in the injection channel (6.8 mm length) in 50 s. We switched the power supply to the anode reservoir with 250 V and the cathode reservoir with 0 V. Two amplicons were successfully separated in the separation channel (17 mm length) in 4 min. In order to assign the peak in the electropherogram, we added two bracket ladders with the amplicon sample, so that we could accurately identify the target peak based on a relative migration time.