Binary-number-based digital electrochemical detection using a single working electrode with multiple sensors

While digital detection improves the sensitivity of electrochemical analysis, adapting it for array-based high-throughput assays has been challenging. The reason is that when integrating many electrochemical sensors in a small chip device, there may not be sufficient space for multiple lead connections to the external equipment. Here, we propose a new approach to prepare multiple sensors on one working electrode, and use the device for simultaneous digital electrochemical detection of droplet arrays. Based on the binary number system, sensor electrodes 4, 2, and 1 mm² in size are prepared on a single working electrode, and droplets with or without a target redox compound are placed on each sensor. The total signal from the working electrodes is converted to a three-digit binary number that specifies the presence or absence of the analyte at each position. Therefore, the droplets can be monitored simultaneously via a single line. This new concept allows us to prepare multiple electrochemical sensors on a small device for digital detection and digital imaging.