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1. A SWEAT-BASED SELF-CHARGING POWER SYSTEM: INTEGRATION OF MICROBIAL ENERGY HARVESTING AND STORING DEVICES

   Gao, Yang; Choi, Seokheun (June 2022, Technical digest SolidState Sensor Actuator and Microsystems Workshop)

   We demonstrate the first example of a wearable self-charging power system that offers (i) the high-energy harvesting function of a microbial fuel cell (MFC) and (ii) the high-power operation of a supercapacitor through charging and discharging. The MFC uses human skin bacteria as a biocatalyst to transform the chemical energy of human sweat into electrical power through bacterial metabolism, while the integrated supercapacitor stores the generated electricity for constant and high-pulse power generation even with the irregular perspiration of individuals. The all-printed paper-based power system integrates the horizontally structured MFC and the planar supercapacitor, representing the most favorable platform for wearable applications because of its lightweight and easy integrability into other wearable devices. The self-charging wearable system attains higher electrical power and longer-term operational capability, demonstrating considerable potential as a power source for wearable electronics. 

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2. PV to Vehicle, PV to Grid, Vehicle to Grid, and Grid to Vehicle Micro Grid System Using Level Three Charging Station

   https://doi.org/10.1109/GreenTech52845.2022.9772041  

   Balal, Afshin; Giesselmann, Michael (March 2022, 2022 IEEE Green Technologies Conference (GreenTech))

   This paper makes use of electric vehicles (EVs) that are simultaneously connected to the Photovoltaic Cells (PV) and the power grid. In micro-grids, batteries of the electric vehicles (EVs) used as a source of power to feed the power grid in the peak demands of electricity. EVs can help regulation of the power grid by storing excess solar energy and returning it to the grid during high demand hours. This paper proposes a new architecture of micro-grids by using a rooftop solar system, Battery Electric Vehicles (BEVs), grid connected inverters, a boost converter, a bidirectional half-bridge converter, output filter, including L, LC, or LCL, and transformers. The main parts of this micro-grid are illustrated and modeled, as well as a simulation of their operation. In addition, simulation results explore the charging and discharging scenarios of the BEVs. 

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3. Dual-Transduction Electromechanical Receiver for Near-Field Wireless Power Transmission

   https://doi.org/10.1109/MEMS51782.2021.9375416  

   Smith, Spencer E.; Halim, Miah A.; Rendon-Hernandez, Adrian A.; Arnold, David P. (January 2021, 2021 IEEE 34th International Conference on Micro Electro Michancial Systems (MEMS))

   null (Ed.)

   We report the design, fabrication, and experimental characterization of a chip-sized electromechanical micro-receiver for low-frequency, near-field wireless power transmission that employs both electrodynamic and piezoelectric transductions to achieve a high power density and high output voltage while maintaining a low profile. The 0.09 cm 3 device comprises a laser-micro-machined titanium suspension, one NdFeB magnet, two PZT-5A piezo-ceramic patches, and a precision-manufactured micro-coil with a thickness of only 1.65 mm. The device generates 520 μW average power (5.5 mW•cm -3 ) at 4 cm distance from a transmitter coil operating at 734.6 Hz and within safe human exposure limits. Compared to a previously reported piezoelectric-only prototype, this device generates ~2.5x higher power and offers 18% increased normalized power density (6.5 mW•cm -3 •mT -2 ) for potential improvement in wirelessly charging wearables and bio-implants. 

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4. A Long-Lasting Microliter-Scale Microbial Biobattery Using Solid-State Ionics

   Mohammadifar, Maedeh; Choi, Seokheun (January 2018, 18th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2018))

   We report a microliter-scale bacteria-powered biobattery providing a long-term operational capability for potentially powering unattended wireless sensor networks. In a 20μL-chamber, the biobattery contained a horizontally arranged anode/salt-bridge/cathode configuration with solid-state agar electrolytes. A slow release of bacterial nutrients from a synthetic solid anolyte enabled a continuous current generation (> 6μA/cm2) over 8 days while a liquid-based anolyte was completely depleted within 4 hours. Given that wireless sensors require an ultra-low power intermittently, our micro-biobattery can be practically used for more than a month without human intervention. Agar-based catholyte and salt bridge further enhanced the device lifespan and ensured its practical feasibility as a power source for wireless sensors. The device was sealed with a gas-permeable polydimethylsiloxane (PDMS) membrane to facilitate gas exchange to the bacteria and cathodic reactions, even ideally allowing for replenishing bacterial nutrients from environments for self-sustainable energy harvesting. Our device used Shewanella oneidensis MR-1 to produce a maximum power density of 4μW/cm2 and current density 45μA/cm2 after 96 hours (day 4), which will be enough power for small-power applications. 

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5. An Electrodynamic Wireless Power Receiver ‘Chip’ for Wearables and Bio-implants

   https://doi.org/10.1109/WoW47795.2020.9291290  

   Halim, Miah A.; Rendon-Hernandez, Adrian A.; Arnold, David P. (November 2020, 2020 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW))

   null (Ed.)

   This paper presents the design, fabrication and experimental characterization of a chip-sized wireless power receiver for low-frequency electrodynamic wireless power transmission (EWPT). Utilizing a laser micro-machined meandering suspension, one NdFeB magnet, and two PZT-SA piezoelectric patches, this 0.08 cm 3 micro-receiver operates at its torsion mode mechanical resonance of 724 Hz. The device generates 360 μW average power (4.2 mWcm -3 power density) at 1 cm distance from a transmitter coil operating at 724 Hz and safely within allowable human exposure limits of 2 mTrms field. Compared to a previously reported macro-scale prototype, this volume-efficient micro-receiver is 31x smaller and offers 3.2x higher power density within a low-profile, compact footprint for wirelessly charging wearable and bio-implantable devices. 

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