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A wearable energy harvester (EH) incorporating a face mask with a thermoelectric generator is demonstrated. The function of this device is to generate electrical power from the heat produced by the human body, particularly breath, with the specific aim of powering wearable sensor applications. A prototype was built using a commercially available N95 face mask, a thermoelectric generator, and a heatsink. The performance of this EH device was assessed using experimental and numerical methodologies. The experimentally tested power output of the prototype was found to be ≈100 µW, with a corresponding power density of ≈30 µW/cm3, for a temperature difference of 7°C. [ABSTRACT FROM AUTHOR]

This study demonstrates an energy harvester that combines a piezoelectric nanogenerator and an electret-based electrostatic generator. The device consists of an in-house fabricated nanocomposite (polydimethylsiloxane/barium titanate/carbon nanotube) as a piezoelectric layer and a monocharged Teflon fluorinated ethylene propylene as an electret electrostatic layer. The mechanical impedance of the structure can be altered easily by changing the nanocomposite monomer/cross-linker ratio and optimizing various mechanical energy sources. The energy harvester's performance was characterized by performing measurements with different frequencies (5–20 Hz) under applied dynamic loading. A total volumetric power density of ∼8.8 μW cm−3 and a total stored energy of ∼50.2 μJ min−1 were obtained. These findings indicate that this versatile, lightweight, and low-cost energy harvester can be employed as a power supply source for microelectronics in applications, such as wearables. [ABSTRACT FROM AUTHOR]

The influence of leg dimensions and spacing on power-generation and thermo-mechanical performance of thermoelectric devices was investigated using numerical and statistical analyses tools. Bismuth-telluride based thermoelectric device models with rectangular-prism and cylindrical legs were simulated for a temperature range of 20–120 °C and various leg heights between 1 and 5 mm, widths/diameters between 1 and 2 mm, and spacing between 0.5 and 1.5 mm. Predicted power output, conversion efficiencies, and thermal stresses were validated with less than 8.9%, 1.2%, and 6.6% variations respectively. It is found that both leg width and height have a significant effect on power generation and thermal stresses: The relationship between power generation performance and thermal stress levels is inverse. Although leg spacing has effect on thermal stress and conversion efficiency, its effect on power output is negligible. [ABSTRACT FROM AUTHOR]

There is an increasing need for non-destructive, low-cost devices for real-time fluid viscosity monitoring. Therefore, in this study, a method based on structural health monitoring is adapted for monitoring fluid properties. A device is built such that an inexpensive and disposable viscosity probe be possible. The design incorporates a sensor/actuator pair using a piezoelectric material layered with copper/brass and capable of monitoring viscosity changes in low volume liquids (e.g., vacutainer vial). Experiments performed with the new device show a definite pattern of wave propagation in viscous solutions. A numerical model is built to investigate the wave propagation in the fluid. For experimental measurements, the sensor part of the device detects the generated pressure wave in fluid (e.g., air, water, glycerin) by the actuator part. The phase shift between the actuator and the sensor signals is then recorded and plotted for different concentrations of glycerin and water at room temperature. The results of this study show a direct correlation between the phase shift and varying viscosity in the ultrasonic frequency range from 6 to 9 MHz. The numerical simulation, performed utilizing acoustic modal and harmonic response analysis, results also demonstrate the same trend as the experimental results: a phase shift increases with the viscosity of the fluid. [ABSTRACT FROM AUTHOR]