Development of Sustainable Electronic Device for Non-Enzymatic Glucose Sensing through Extended-Gate-Based Organic Field Effect Transistors
Authors: Singh Kshitij RB , Rai Harshita , Pradhan Safalmani , Pandey Shyam S. 
Published: December 2024

Diabetes is one the most common problem and can lead to kidney failure and other deadly medical conditions if not monitored properly. The pre-existing techniques for monitoring diabetes utilize enzymes, which makes the technique costly, sophisticated, and temperature-dependent storage restricts its broad utilities and to circumvent this drawback of pre-existing techniques, label-free detection of glucose is highly desired. Thus, in this study, CuO/MXenes were synthesized by adopting an ex-situ synthesis approach. Initially, CuO nanoparticles were synthesized using Annona squamosa seed extract as per the previous report. Then, MXenes were synthesized and mixed with CuO nanoparticles in equal ratios, then the mixed solution was kept for stirring at 600 rpm for 8 hours in an inert atmosphere at 80oC. Further, the synthesized CuO/MXenes nano-composites were initially characterized for its optical, structural, and morphological characteristics and then screen printed on indium tin oxide (ITO) glass substrate for utilizing it as an extended-gate electrode. Further, the organic field effect transistor (OFET) was then fabricated by utilizing three different conjugated polymers, namely RR-P3HT, NR-P3HT, and DPP-TTT as a semiconductor material in the bottom gate top contact device architecture and utilized as a transducer for the label-free sensing of glucose via CuO/MXenes nanocomposite. The sensing electrode was connected to a transduction unit (OFET) by extending the gate and all the experiments were performed by applying gate voltage via the reference electrode (schematically shown in Figure 1) under optimized pH condition of 50 mM phosphate buffer saline (PBS; 0.9% NaCl; pH 7) solution containing 5 mM [Fe(CN)6]3−/4−. The main objective of this study is to understand the mobility effect on sensing characteristics, so three different OFETs were fabricated from low to high mobility (order 10-1 to 10-3). Moreover, before sensing glucose, the operation of the OFET was validated before connecting to the extended gate and after connecting to the extended gate (with a blank PBS solution), which demonstrated typical p-type OFET characteristics associated with various polymers. Further, during sensing studies in the presence of glucose solution, there was a clear shift in the threshold voltage (Vth). These extended gate OFETs demonstrated a good response time, but the higher mobility OFET demonstrated rapid determination of glucose in just 20 seconds. There was a linear shift in the threshold voltage (Vth) as a function of the increasing glucose concentration varying from 2 to 100 mM. Details about sensitivity and selectivity will be discussed in detail during the presentation; apart from the mentioned studies, we have also compared the performance of our fabricated transduction unit with the commercially available electrochemical transduction unit for sensing glucose. However, from the results of this study, it is evident that the mobility of OFETs plays a major role in sensing.

Figure 1