Flexible micro-sensors with self-assembled graphene on a polyolefin substrate for dopamine detection

The electrochemical sensing of dopamine is of great significance for studying and treating neurochemical diseases due to its potential feasibility for in vivo diagnostics. The commonly used sensors suffer from low sensitivity, the interference of ascorbic acid, and poor flexibility. In this paper, the function of electrode substrates including polyolefin, polystyrene, and polyethylene terephthalate films were investigated for their ability to improve electrochemical performances and provide favorable flexibility. The interference from ascorbic acid was cut down to a minimum by reducing the electrochemical resistance and the ascorbic acid diffusion current. The results demonstrate that gold electrodes prepared on polyolefin films exhibit a low charge transfer resistance of about 20 Ω, high sensitivity of dopamine detection (7.8 μA/μM), which is about 312 folds that of silicon electrode (0.025 μA/μM) and excellent flexibility. Having regulated the fabrication process of graphene by altering self-assembly layers and modification area, the sensor shows a dopamine detection limit of 0.11 μM in the presence of 500 μM ascorbic acid, and a sensitivity of 0.33 μA/μM. This work is valuable for the further improvement of the sensitivity and selectivity of the electrochemical sensor.