Fabrication of a Flexible and Handmade Electrochemical Sensor for Rapid Simultaneous Detection of Acetaminophen and Caffeine

There has been a growing interest in portable, flexible, and disposable electrochemical sensors in recent years due to their low cost, simplicity, and excellent analytical performance. Despite significant advancements in the field, the demand for low-cost, high-performance electrodes remains challenging. In this study, a flexible and disposable sensor with low-cost and simple fabrication was developed as a sustainable approach. Conductive ink was prepared using nail polish and graphite powder, while polyethylene terephthalate from recycled beverage bottles was repurposed as the sensor substrate. The fabricated electrode was characterized using differential pulse voltammetry (DPV), cyclic voltammetry, scanning electron microscopy, Fourier-transform infrared, and contact angle. The developed flexible screen-printed electrode (FSPE) was employed for the simultaneous detection of acetaminophen and caffeine (CAF). Using the DPV technique, a linear detection range of 50–2000 μM was achieved for both analytes, with limits of detection of 6.53 μM for ACE and 3.10 μM for CAF. Moreover, the FSPE was successfully applied for the simultaneous and individual detection of acetaminophen and caffeine in commonly available commercial pharmaceuticals. A cost analysis revealed that the production cost per FSPE unit is $0.436, considering the raw material costs for producing 100 units.