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1. Vibration Energy Harvester With Piecewise Linear Nonlinear Oscillator and Controllable Gap Size

   https://doi.org/10.1115/DETC2022-89948  

   Veney, Jacob; D’Souza, Kiran (August 2022, Volume 10: 34th Conference on Mechanical Vibration and Sound (VIB))

   Abstract Recently, vibration energy harvesting has been seen as a viable energy source to provide for our energy dependent society. Researchers have studied systems ranging from civil structures like bridges to biomechanical systems including human motion as potential sources of vibration energy. In this work, a bench-top system of a piecewise-linear (PWL) nonlinear vibration harvester is studied. A similar idealized model of the harvester was previously looked at numerically, and in this work the method is adjusted to handle physical systems to construct a realistic harvester design. With the physically realizable harvester design, the resonant frequency of the system is able to be tuned by changing the gap size between the oscillator and mechanical stopper, ensuring optimal performance over a broad frequency range. Current nonlinear harvester designs show decreased performance at certain excitation conditions, but this design overcomes these issues while also still maintaining the performance of a linear harvester at resonance. In this investigation, the system is tested at various excitation conditions and gap sizes. The computational response of the resonance behavior of the PWL system is validated against the experiments. Additionally, the electromechanical response is also validated with the experiments by comparing the output power generated from the experiments with the computational prediction. 

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2. Electrode and electrolyte configurations for low frequency motion energy harvesting based on reverse electrowetting

   https://doi.org/10.1038/s41598-021-84414-3  

   Adhikari, Pashupati R.; Tasneem, Nishat T.; Reid, Russell C.; Mahbub, Ifana (March 2021, Scientific Reports)

   Abstract Increasing demand for self-powered wearable sensors has spurred an urgent need to develop energy harvesting systems that can reliably and sufficiently power these devices. Within the last decade, reverse electrowetting-on-dielectric (REWOD)-based mechanical motion energy harvesting has been developed, where an electrolyte is modulated (repeatedly squeezed) between two dissimilar electrodes under an externally applied mechanical force to generate an AC current. In this work, we explored various combinations of electrolyte concentrations, dielectrics, and dielectric thicknesses to generate maximum output power employing REWOD energy harvester. With the objective of implementing a fully self-powered wearable sensor, a “zero applied-bias-voltage” approach was adopted. Three different concentrations of sodium chloride aqueous solutions (NaCl-0.1 M, NaCl-0.5 M, and NaCl-1.0 M) were used as electrolytes. Likewise, electrodes were fabricated with three different dielectric thicknesses (100 nm, 150 nm, and 200 nm) of Al₂O₃and SiO₂with an additional layer of CYTOP for surface hydrophobicity. The REWOD energy harvester and its electrode–electrolyte layers were modeled using lumped components that include a resistor, a capacitor, and a current source representing the harvester. Without using any external bias voltage, AC current generation with a power density of 53.3 nW/cm²was demonstrated at an external excitation frequency of 3 Hz with an optimal external load. The experimental results were analytically verified using the derived theoretical model. Superior performance of the harvester in terms of the figure-of-merit comparing previously reported works is demonstrated. The novelty of this work lies in the combination of an analytical modeling method and experimental validation that together can be used to increase the REWOD harvested power extensively without requiring any external bias voltage. 

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3. Power Scavenging Microsystem for Smart Contact Lenses

   https://doi.org/10.1002/smll.202401068  

   Pourshaban, Erfan; Karkhanis, Mohit U.; Deshpande, Adwait; Banerjee, Aishwaryadev; Hasan, Md Rabiul; Nikeghbal, Amirali; Ghosh, Chayanjit; Kim, Hanseup; Mastrangelo, Carlos H. (March 2024, Small)

   Abstract On‐the‐eye microsystems such as smart contacts for vision correction, health monitoring, drug delivery, and displaying information represent a new emerging class of low‐profile (≤ 1 mm) wireless microsystems that conform to the curvature of the eyeball surface. The implementation of suitable low‐profile power sources for eye‐based microsystems on curved substrates is a major technical challenge addressed in this paper. The fabrication and characterization of a hybrid energy generation unit composed of a flexible silicon solar cell and eye‐blinking activated Mg–O₂metal–air harvester capable of sustainably supplying electrical power to smart ocular devices are reported. The encapsulated photovoltaic device provides a DC output with a power density of 42.4 µW cm⁻²and 2.5 mW cm⁻²under indoor and outdoor lighting conditions, respectively. The eye‐blinking activated Mg–air harvester delivers pulsed power output with a maximum power density of 1.3 mW cm⁻². A power management circuit with an integrated 11 mF supercapacitor is used to convert the harvesters’ pulsed voltages to DC, boost up the voltages, and continuously deliver ≈150 µW at a stable 3.3 V DC output. Uniquely, in contrast to wireless power transfer, the power pack continuously generates electric power and does not require any type of external accessories for operation. 

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4. On a self-tuning sliding-mass electromagnetic energy harvester

   https://doi.org/10.1063/5.0005430  

   Bukhari, M.; Malla, A.; Kim, H.; Barry, O.; Zuo, L. (September 2020, AIP Advances)

   Prior research has investigated resonators capable of self-tuning through the use of a sliding mass. This passive tuning mechanism can be utilized to improve vibration control; however, little is known about the nonlinear dynamic interactions between the vibrating beam and sliding mass, particularly as these apply to vibration energy harvesting applications. This paper investigates this problem by numerically and experimentally examining the response of an electromagnetic self-tuning energy harvester. We present the governing equations of this electromagnetic cantilever beam with a sliding mass using the extended Hamilton principle. These equations are then discretized using the Galerkin method and solved numerically. An experiment is carried out to validate the numerical analysis. Parametric studies are conducted to examine the effect of different system parameters on the performance of the self-tuning harvester. 

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5. Battery-Free Wireless Video Streaming Camera System

   https://doi.org/10.1109/RFID.2019.8719264  

   Saffari, Ali; Hessar, Mehrdad; Naderiparizi, Saman; Smith, Joshua R. (April 2019, 2019 IEEE International Conference on RFID (RFID))

   We design and prototype the first battery-free video streaming camera that harvests energy from both ambient light and RF signals. The RF signals are emitted by a nearby access point. The camera collects energy from both sources and backscatters up to 13 frames per second (fps) video at a distance of up to 150 ft in both outdoor and indoor environments. Compared to a single harvester powered by either ambient light or RF, our dual harvester design improves the camera's frame rate. Also, the dual harvester design maintains a steady 3 fps at distances beyond the RF energy harvesting range. To show efficacy of our battery-free video streaming camera for real applications such as surveillance and monitoring, we deploy our camera for a day-long experiment, from 8 AM to 4 PM, in an outdoor environment. Our results show that on a sunny day, our camera can provide a frame rate of up to 9 fps using a 4.5 cm×2.2 cm solar cell. 

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