Smartphone-based square wave voltammetry system with screen-printed graphene electrodes for norepinephrine detection

In recent years, researchers have begun to develop smartphone-based electrochemical system to support healthcare services. These systems are always combined with screen-printed electrodes to perform early diagnosis, chronic disease monitoring, and health management. However, there are still some challenges that will affect the practical application of the systems with the electrodes, such as system sensitivity, sensor performance, and sensor stability. In this paper, a smartphone-based square wave voltammetry system with screen-printed graphene electrodes was developed to solve the aforementioned challenges. The system composed of sensors, coin-sized detector, and smartphone. Graphene ink was printed on soft substrate to construct flexible screen-printed graphene electrode. The electrodes were used as disposable sensors, exhibited high electron transfer rate and low contact resistance. Meanwhile, the rate of current change of the electrodes remained nearly unchanged for one month. The detector was used to generate electrochemical excitation signals, monitor the resultant currents on the sensors, convert the current into digital code, and send them to smartphone. The smartphone acted as the core of the system for system control, data processing, and results display. Then, the system with the electrodes was used for norepinephrine detection. The limit of detection for norepinephrine was as low as 0.265 ​μM with 3δ/slope calculation for the dose-dependent fitting curve. It has also been verified to be able to distinguish norepinephrine from other representative interfering substances in the body. Hence, the system with flexible screen-printed graphene electrodes showed great potential in the field of point-of-care testing and wearable detection.