Influence of Thickness of Screen Printed Carbon Electrodes on Electrochemical Sensing

Screen printing is one of the widely used methods for printed sensors and electronics. The performance of these devices could vary with the printing parameters such as thickness of the printed layer, the squeeze length and pressure applied for printing etc. Whilst sensor design and the ink used for the printing of sensitive layers have been studied previously, the vital printing parameters has not attracted much attention. This paper reports the influence of thickness of printed sensor on their electrochemical sensing property. Carbon ink is used to print sensors with three-electrode geometry and their working electrode is modified with MoS2 to study the detection of ascorbic acid. The thicknesses of the sensitive layers varied from ~4 µm to 120 µm as the number of printed layers of ink increased from 1 to 5, 10 and 20. The cyclic voltammetry, differential pulse voltammetry and impedance spectroscopy are used to investigate the electrochemical performance. It was noted that the peak current indicating the oxidation of ascorbic acid at 0.04 V, increased with the increase in the thickness of electrode or the number of printed layers. The higher current values and lower series resistance was measured for layers 10 and 20, indicating the ideal printed thickness of sensors for low power operation and easy interfacing with read out electronics.