Screen printing is a known method to produce disposable and low-cost sensors. Depending on the application such as food analysis, environmental health monitoring, disease detection and toxin detection, screen-printed electrodes can be fabricated in a variety of sizes and shapes. Modification of the electrode's material and geometrical dimension may be done to produce effective screen-printed three-electrodes system. Thus, the effects of varying the working electrode (WE) area in radius of 0.9 mm to 2 mm, gap spacing between electrodes ranging from 0.5 mm to 1.6 mm, and the width of the counter electrode in range of 0.7 to 1.3 mm on sensor's performance was investigated in this study through COMSOL simulation. It was found that the modification of the working electrode radius and the gap between the electrodes has the most significant effect on sensor's performance, while modifying the width of the counter electrode (CE) shows no significant effect. Sensors with 0.9 mm radius or 2.54 mm² WE area and 0.5 mm gap spacing has shown the optimum performance with 0.026 A/m² current density which is contributed by 0.044 pF capacitance value. As a conclusion, regardless of the width of counter electrodes, a smaller gap between electrodes and a smaller working area would lead to optimal performance of a screenprinted three-electrode sensor system.

The screen-printed electrode (SPE) sensor is widelyemployedin food analysis, environmental health monitoring, disease detection, toxin detectionandother applications.As it is crucial for the SPE sensor to have an outstanding performance, this study examined the effects of manipulatingthe working electrode(WE)radius, gap spacing between electrodes, and counter electrode (CE) width on the performance of an SPE sensor.Finite element simulation on various geometrical dimensions was done prior to screen-printed electrode SPE sensor’s fabrication at Jabil Circuits Sdn Bhd.The electrodes performance is measured throughcyclic voltammetry (CV)using a potentiostat at an optimum scan rate of0.01 V/s andavoltammetry potential window range of -0.2 to 0.8 Vin 0.01 MPhosphate Buffered Saline (PBS) solution.It is discovered that adjusting the WE area and the gap separation between the electrodes had the most impact on sensor performance compared to varying the CE width. In both simulation and CV measurements, WE with the highestradius of 0.9 mmwith aneffectivearea of 2.54 mm2, and the smallestgap spacing of 0.7 mm has shown the highest current density of 0.04 A/mm2(simulation) and 0.3 μA/mm2(experiment) which can be translated as the highest sensitivity for the SPE sensor.Further CV measurement in nicotine sensing application has proven that the SPE sensor can effectively detect the nicotine oxidation indicating itspromising potential as a biosensor. Combination of optimum SPE dimension together with suitableelectrode modificationprocessservesas the basis for an effective and sensitive SPE sensor for various biosensing applications.