Kunal Wadhwani received his MS Dual Degree in Electronics and Communication Engineering (ECE). His research work was supervised by Dr. Syed Azeemuddin. Here’s a summary of his research work on Solvent based Optimization of RF Sensor Design for Enhanced Sensitivity in Bio-sample Detection:
Radio frequency (RF) sensing is emerging as an alternative for quantitative analysis of bio-samples due to its advantages over conventional techniques. It is robust, reusable, portable, less cumbersome and the quantity of sample is typically in micro-litres. Planar resonant sensors like complementary split ring resonators (CSRR) and inter-digitated capacitors (IDC) are the most excellent choices for bio-sample detection due to simple design, low cost fabrication, compactness and effortless integration with other components for lab on chip development for various RF applications. CSRR based RF sensor has been designed of size 38 x 32 mm2 is designed with resonant frequency at 1.51 GHz. The designed sensor is fabricated on a 1.6 mm thick FR4 substrate with copper of thickness 0.035 mm on both sides. Quantitative analysis of sucrose, glucose, fructose and L-Lysine have been performed using Keysight Vector Network Analyzer (VNA). Although this sensor is advantageous in various aspects, existing sensors still suffer from a lack of sensitivity in detecting minuscule changes in the dielectric constant.
The major work presents the optimization of RF cavity design using binary particle swarm optimization (BPSO) for quantitative analysis of L-Lysine, extendable to any bio-sample. The design of the sensor is broken into fragments called cells. A combination of the cells constitutes a cell pattern resulting in a RF design. The cell pattern is optimized in such a way using BPSO to achieve maximum sensitivity for a particular set of dimensions of the sensing region. Usually, sensors are designed in the presence of air which has a dielectric constant of ~1. In contrast, most bio-samples have solvents associated with them. Water and its based solvents having dielectric constant ~79 are most commonly used for bio-sample detection. Therefore, we perform optimization of RF designs like CSRR and IDC for achieving enhanced sensitivity in the presence of the solvent above sensing region, unlike air-based reference. Detecting small changes in the concentration of the sample under test (SUT), which contributed to a minuscule change in the dielectric constant of the solution, has been achieved through optimized RF sensors. The final sensors have been fabricated using the low-cost PCB technology on a FR-4 substrate of dielectric constant ~4.3. An enhancement of 47.38× for the CSRR and 2.03× for the IDC in the detection of L-Lysine at frequencies 2.18 GHz and 0.72 GHz, respectively has been achieved when compared to sensitivities of their traditional counterparts. Moreover, the sensors have been tested to detect sucrose and glucose, and promising results have been obtained. This methodology, called solvent based optimization, can be extended for enhancement of the sensitivity of any planar RF sensor, making it a suitable contender for optimization of next-gen RF bio-sensors. This work shows great potential in various biomedical, agricultural, and pharmaceutical applications.