K. J. Suja

Low-force human-interface systems require very compact sensors that produce measurable electrical responses under small mechanical loads. This work presents a simulation-based study of diaphragm geometry, piezoresistive microstructure and substrate flexibility in a MEMS piezoresistive force-sensing configuration. Finite-element analyses were performed using COMSOL Multiphysics to compare rectangular, meander-shaped and Archimedean spiral p-type polysilicon piezoresistive microstructures under common diaphragm dimensions, sensing-layer material properties and loading conditions. A square silicon diaphragm of 1 mm x 1 mm was selected following an initial comparison of diaphragm geometries and thicknesses. To further analyse the sensor's adaptability and responsiveness on a flexible substrate, an Archimedean spiral configuration was incorporated onto a polydimethylsiloxane (PDMS) substrate. Under the simulated force range of 0 - 5 N and a bridge excitation of 3 V, the rectangular, meander, and Archimedean spiral configurations exhibited normalised sensitivities of 17.7, 18.7, and 21.7 mV/V/N, respectively, while the PDMS-supported spiral configuration exhibited 23.3 mV/V/N. The spiral therefore produced the highest simulated normalised sensitivity among the geometries examined under the specified modelling conditions. Additional centreline stress-strain and mesh-independence analyses were used to strengthen the numerical comparison. A separate geometrically nonlinear analysis indicated that large-deflection effects become appreciable at approximately 0.45 N using the adopted 5 % displacement-deviation criterion; therefore, the 0-5 N sensitivity values are interpreted as comparative baseline predictions rather than absolute large-deflection performance values. The results provide a computational design basis for selecting candidate piezoresistive microstructures for subsequent fabrication and experimental validation in low-force human-interface sensing.

A surface plasmon resonance (SPR)-based D-shaped photonic crystal fiber biosensor has been proposed as an effective technique for detecting cancer. Despite several advanced SPR biosensor designs that have been reported to achieve high sensitivity, most exhibit non-uniform responses toward different cancerous cells and lack reconfigurability. Since sensitivity strongly depends on the plasmonic material, distinct sensors are often preferred for specific cancerous cells. However, previous studies on common cancer types have not explicitly addressed the issue of non-uniform sensitivity across different cells, as the widely varying sensitivity has not been systematically analyzed or treated as a key design concern, thereby limiting the general applicability of existing SPR biosensors. In this work, we define and address this gap for the first time by proposing a reconfigurable SPR-based D-shaped PCF biosensor utilizing an Au/Ge2Sb2Te5 (GST) phase change material (PCM) interface. The distinct crystalline and amorphous phases of GST, exhibiting significant optical contrast, provide dual sensing capability and thereby enable different sensitivity responses for the detection of various cancer cells. In the amorphous GST, high sensitivity is observed for skin (4000nm/RIU), cervical (3333.33nm/RIU), and breast II(MCF-7) cancer (2857.14nm/RIU). In contrast, the crystalline phase exhibits high sensitivity in blood (2857.14nm/RIU), adrenal (2857.14nm/RIU), and breast I (MDA-MB-231) cancer (2857.14nm/RIU). Thus, by switching the GST phase, the sensor can be reconfigured to select different cancerous cells. Hence, the reconfigurability of the PCM effectively mitigates the issue of non-uniform sensitivity of conventional SPR-based biosensors, demonstrating the strong potential and versatility for futuristic biosensing technologies.

Ohmic heating has emerged as an effective alternative to conventional thermal treatments for fruit juice preservation. However, the performance of an ohmic heating system is strongly influenced by the excitation waveform generated by its power electronics circuitry. Conventional systems typically employ square‐wave excitation, which can produce rapid temperature rises and may adversely affect nutrient retention. There is therefore a need for alternative excitation waveforms that provide better control over the temperature rise while maintaining effective microbial inactivation. To address this need, this work proposes a novel ohmic heating system comprising a custom‐designed square‐wave generator and an RC differentiator that converts the square‐wave output into exponentially decaying pulses. The square‐wave generator is designed to deliver the voltage and current levels required for juice treatment, and the RC differentiator enables controlled energy delivery to the load by optimising the pulse width. The proposed circuit produces high‐amplitude, short‐duration exponential pulses with a peak electric field intensity of 140 V/cm and an optimised pulse width of 46 μ s. The treatment system was analysed and experimentally validated using watermelon juice as the treatment medium. Experiments were conducted with electrode gaps ranging from 5 mm to 20 mm, operating frequencies of 1 kHz and 10 kHz and a maximum treatment temperature of 70°C. The influence of the generated exponential pulses on treatment performance was evaluated through microbial inactivation studies with Escherichia coli and nutrient retention measurements of vitamin C and total antioxidant activity. Experimental results showed that with the maximum treatment temperature limited to 70°C, the optimised differentiator‐based system achieved a bacterial log reduction of 5.98 after 2.5 min, compared with 3.92 for the conventional square wave–driven system after 0.5 min. The proposed excitation method also maintained good nutrient retention characteristics while operating below 70°C. The results suggest that differentiator‐based pulse shaping can improve the effectiveness of ohmic heating systems and highlight the potential of customised waveform‐generation techniques for electric field–based food processing applications.

Ideal sensors for detection are a critical issue faced in real-world applications, which keeps the research activities in the field of sensors active, especially in the health sector, to diagnose and prognosis the disease in advance and non-invasive ways (such as breath analyzers). In this work, a prototype of sensor detection for Cholesterol abnormalities (root cause for Cardiovascular disease) is concentrated. Isoprene (C ₅ H ₈ ) is the breath biomarker observed during cholesterol abnormalities. To minimize the complex lithography challenges, optical activation (Deep-UV LED, $\lambda $ = 300 nm) is focused on sensing Isoprene with Titanium dioxide/Tungsten oxide (TiO ₂ /WO ₃ ) nanocomposites (NCs). Defect engineering of WO ₃ by the addition of TiO ₂ nanoparticles is concentrated, and it is optimized with the aid of X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence (PL) to determine the Charge Accumulation Layer (CAL). Isoprene is detected in the range of 20 ppb (Abnormal cholesterol) to 80ppb (Normal Cholesterol) by the optimized detection layer with an enhancement of 79.5% in sensitivity with a 1.5 min response time and 25 sec recovery time during the deployment of the UV-activated technique. Apart from the miniaturization limitations faced for fabricating a sensor prototype, the critical point is cross selectivity. Hence, the detection layer is ratified in the presence of other contents of breath such as CO ₂ , NH ₃ , NO and CO and the sensor could achieve an average selectivity of 10.53% compared to the state of art VOC sensors.