Paper-based Two-electrode Sensor fabricated by Pencil Drawing for Glucose Sensing

Recent advances in sustainable and low-cost sensing strategies pave a new way for the design and fabrication of paper-based sensors employing allotropes of carbon. This article demonstrates the design and fabrication of a paper-based sensor using an 8B graphite pencil and its application towards glucose sensing. The sensor utilizes Whatman filter paper as substrate and two pencil-drawn electrodes (PDEs) as glucose sensing probes. Electrochemical behaviour of the sensor is analyzed using cyclic voltammetry in glucose ambiance. The adsorption of glucose on the electrode’s surface shows an infinitesimal change in the current response which ascertains an adsorption-controlled reaction of glucose with single-or multilayer graphene formed on the paper substrate during manual exfoliation of the 8B graphite pencil. Moreover, electrochemical impedance spectroscopy of the pencil-drawn sensor (PDS) reveals a considerably low charge transfer resistance for PDS when exposed to glucose. Upon chronoamperometric evaluation, the PDS shows a sensitivity of 1.044 $\mu \mathrm{Am}^{-1} \mathrm{~cm}^{-2}$, fair linearity of 1.2 $\mu$M-80$\mu$M, and a limit of detection of 1.27 $\mu$M. Thus, these kinds of cost-effective sensors are suitable for glucose sensing and offer an opportunity for developing lab-on-chip applications.