This work presents a strip-format enzymatic glucose-sensing working electrode based on a glucose oxidase/chitosan(GOx/Chitosan) sensing layer deposited on all-carbon conductive 6x6 micropillar arrays. The micropillar architecture was fabricated to increase the electrode surface area. The working electrodes were fabricated by UV photolithography followed by carbon microelectromechanical systems (C-MEMS) on a Si/SiO₂ substrate used as a temporary support. Surface morphology was characterized by SEM, and the presence of the GOx/chitosan functionalization was supported by Raman and FTIR spectroscopy. Electrochemical characterization was performed in a three-electrode configuration (Ag/AgCl reference, Pt counter) using cyclic voltammetry(CV) and amperometry. The GOx/chitosan functionalized micropillar electrode exhibited glucose-dependent amperometric response over 0.8–15 mM, with a sensitivity of 9.41 × 10⁻³ mA mM⁻¹ (R² = 0.97) and a calculated limit of detection of 1.72 mM. Under the tested conditions, common interferents (ascorbic acid, uric acid, dopamine, fructose) produced < 1
This work reports a simulation-based optimization and comparison between two hybrid piezoelectric-electromagnetic vibration energy harvesters (VEHs) featuring different beam geometries: curved T-shaped trapezoidal and rectangular. Both designs are evaluated under identical vibrational conditions using finite element analysis, analytical, and numerical modeling. The hybrid harvesters consist of a piezoelectric layer bonded to the beam and a magnetic proof mass oscillating above a planar coil. The performance of both systems was systematically analyzed based on parameters such as tip displacement, strain distribution, induced piezoelectric voltage, and electromagnetically induced current. Under a 1 mm base excitation, the trapezoidal beam shows a higher tip displacement of 28.7 mm at a resonance frequency of 24 Hz. In comparison, the rectangular beam achieves a displacement of 9.8 mm at its resonance frequency of 24 Hz. The second resonance frequency occurs at 45 Hz for the trapezoidal beam, with a tip displacement of 4.7 mm, compared to 1.75 mm at 42 Hz for the rectangular beam. Results demonstrate that the trapezoidal beam design outperforms the rectangular beam counterpart in multiple aspects, such as higher tip displacement and velocity. Consequently, the piezoelectric output voltage increases by approximately 104.89
This work presents the design, fabrication, and experimental characterization of an aluminum nitride (AlN)-coated microelectromechanical system (MEMS) resistive cantilever sensor for carbon dioxide (CO₂) detection. The cantilever structures were fabricated using a combination of surface and bulk micromachining techniques on silicon substrates with a silicon nitride structural layer to enhance mechanical stability. Morphological characterization was performed using field-emission scanning electron microscopy (FESEM), while dynamic response and resonance characteristics were evaluated using Laser Doppler Vibrometry (LDV). The influence of cantilever arm length on structural integrity and resonance frequency was systematically investigated, followed by proof-of-concept CO₂ sensing using the selected mechanically stable geometry. The fundamental resonance frequency decreased from 729 kHz for the shortest device (120 μm, Q1) to 120 kHz for the longest device (270 μm, Q4); the 270 μm device exhibited a second harmonic at 230 kHz. Gas-sensing measurements were performed on the mechanically stable 120 μm (Q1) cantilever at a fixed CO₂ concentration of 1000 ppm. Its resistance decreased from 1.20 × 10⁸ Ω to 5.39 × 10⁷ Ω, corresponding to a single-point relative response of approximately 55.2
In this work, a micro heater enabled gas sensor based on a nano crystalline WO3 - TiO2 composite is developed for the selective detection of nitrogen dioxide (NO2) gas. A detailed comprehensive analysis of micro-heater materials was carried out to evaluate their thermal efficiency leading to the selection of tungsten (W) as an optimal material due to its stability and ability to generate high temperatures at low bias voltage. The micro heater plays a crucial role in establishing a uniform and controlled temperature profile, which significantly enhances gas adsorption and minimizes the effects of humidity. Prior to fabrication, the sensor is designed and analyzed using finite element method (FEM) based multiphysics simulations. The optimized micro heater configuration enabled the device to achieve an ideal operating temperature of approximately 453.15 K under low-voltage conditions. The WO3 (95%) - TiO2 (5%) composite sensing layer was synthesized and characterized using scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray Diffraction (XRD) confirming its nanocrystalline structure. The presented sensor exhibits a high response of 82% toward NO2 gas, demonstrating the effectiveness of combining an optimized micro-heater design with heterostructured sensing materials for enhanced gas sensing performance.
This paper examines titanium-based phononic crystal reflectors used in a surface acoustic wave resonator to replace a conventional grating reflector. The proposed phononic crystal generates a wide band gap from 960 MHz to 1900 MHz and reflects the escaped acoustic energy back into the resonator body. The phononic crystal periodic structure consists of square titanium pillars repeatedly patterned on a 15 degrees YX LiNO3/SiO2/silicon plate. In addition to bandgap reflection, when designing phononic crystal reflector materials (titanium) that differ from electrode materials (aluminum), acoustic wave reflection increased due to an increase in acoustic impedance (impedance mismatch between the electrode and phononic crystal materials). The study shows that the phononic-crystal bandgap can be tuned by varying the height, width, and material of the periodically arranged square pillars. After applying Square-titanium-based phononic crystal reflectors to the resonator, the stored energy was enhanced, and the loss was reduced compared with the resonator using traditional reflector gratings. The resonator achieves a Bode Q equal to 1800, presenting a 2.76-fold enhancement over a resonator with a conventional reflector. The finite element method (FEM) is employed to analyze the resonance behavior of defect-engineered phononic-crystal structures.
