Miniaturized Portable Handheld Electrochemiluminescence Imaging System with Open Paper Bipolar Electrode

Abstract

Electrochemiluminescence (ECL) is the property of several materials to emit light on application of the external voltage leading to a chemical reaction. Usually, different set of electrodes are necessary to perform the ECL reaction. Recently, bipolar electrode (BPE) based ECL sensing devices have become more popular and received more attention because of the absence of background signal, high specificity, good selectivity, simplified instrumentation and good controllability. Two types of BPEs have been widely reported, open bipolar electrode (OBE) and closed bipolar electrode (CBE). In CBE, both anode and cathode of BPE are separated from each other, and the current flows in two half cells through the BPE only, while in OBE, the microchannel itself acts as a conductor. During the ECL based analysis, BPE is immersed between two driving electrodes (DE) and there is no direct connection between BPE and driving voltage (DV). When sufficient driving voltage (DV) is applied to DE, the electric field is produced across the microchannel, which initiates oxidation and reduction reaction at the two opposite poles of the BPE, leading the generation of ECL signal at the edge of anode. Conventionally, screen printing based BPEs have been reported, which are time-consuming, expensive, and required more fabrication steps. In this work, novel ink jet printing fabrication technique has been adopted on paper substrate to realize paper-BPE-ECL (P-PBE-ECL) system and its application in ECL detection has been validated. Android smartphone was efficiently used to sense ECL signals as well as to drive the required voltage to the open bipolar electrodes (OBEs). If the potential difference between two electrodes is sufficient enough then on electrode surface, oxidation and reduction were carried out simultaneously. Here, required optimised design of P-BPE-ECL with all dimensions was drawn in CorelDraw 7. DEs and BPE were fabricated using ink jet printer shown in Fig. 1. Next, mask preparation was carried out using wax coting on A-4 copier paper followed by mask alignment on ink printed paper, and passing through hot laminator to form hydrophilic and hydrophobic zone. Finally, 3D printed black box with device holder, DC-DC buck boost converter and android smartphone based miniaturised portable handheld system was developed to captured the ECL signal. Herein, luminol reacted with H2O2 to generate ECL signal and the generated ECL signal was captured by an android smartphone. During ECL reaction, H2O2 sensing is the basics to determine glucose. With the optimized parameters, P-BPE-ECL imaging system was successfully used to detect Hydrogen Peroxide (H2O2) with a linear range of 100 μM to 1000 μM with a limit of detection (LOD) 0.13 μM (R² = 0.9771, n=3). Overall, the developed miniaturized, low-cost Electrochemiluminescence platform can be suitably used in many areas such as point-of-care, environmental monitoring, and in biomedical applications.Fig. 1. Schematic illustration of ink-jet printing fabrication for the P-BPE-ECL devices. a) Schematic of P-BPE-ECL with driving electrodes (DE) and BPE device with hydrophilic and hydrophobic zone, b) 3D printed black box with device holder, DC-DC buck boost converter and android smart phone and c) H2O2 vs ECL Intensity with the inset showing the linear behavior of the detection of low concentrations of H2O2 detection. Figure 1