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1. 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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2. Strongly (001) Oriented Bimorph PZT Film on Metal Foils Grown by rf ‐Sputtering for Wrist‐Worn Piezoelectric Energy Harvesters

   https://doi.org/10.1002/adfm.201801327  

   Yeo, Hong Goo; Xue, Tiancheng; Roundy, Shad; Ma, Xiaokun; Rahn, Christopher; Trolier‐McKinstry, Susan (July 2018, Advanced Functional Materials)

   Abstract For piezoelectric energy harvesters, a large volume of piezoelectric material with a high figure of merit is essential to obtain a higher power density. The work describes the growth of highly (001) oriented sputtered lead zirconate titanate (PZT) films (f≈ 0.99) exceeding 4 µm in thickness on both sides of an Ni foil to produce a bimorph structure. These films are incorporated in novel wrist‐worn energy harvesters (<16 cm²) in which piezoelectric beams are plucked magnetically using an eccentric rotor with embedded magnets to implement frequency up‐conversion. The resulting devices successfully convert low‐frequency vibration sources (i.e., from walking, rotating the wrist, and jogging) to higher frequency vibrations of the PZT beams (100–200 Hz). Measured at resonance, six beams producing an output of 1.2 mW is achieved at 0.15 G acceleration. For magnetic plucking of a wrist‐worn nonresonant device, 40–50 µW is produced during mild activity. 

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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. A 1.51 V pH neutral redox flow battery towards scalable energy storage

   https://doi.org/10.1039/C9TA01469A  

   Luo, Jian; Wu, Wenda; Debruler, Camden; Hu, Bo; Hu, Maowei; Liu, T. Leo (April 2019, Journal of Materials Chemistry A)

   Aqueous redox flow batteries using low-cost organic and inorganic active materials have received growing interest for sustainable energy storage. In this study, a low-cost, high redox potential (1.08 V vs. NHE) and high capacity ammonium bromide (NH 4 Br, 214.4 A h L −1 ) catholyte was coupled with an organic viologen anolyte to demonstrate 1.51 V high voltage (SPr) 2 V/Br − aqueous redox flow batteries under pH neutral conditions for the first time. Benefitting from the high water solubility of both the NH 4 Br catholyte and (SPr) 2 V anolyte, the newly designed (SPr) 2 V/Br − organic flow battery was operated at up to 1.5 M and an energy density of up to 30.4 W h L −1 . Using multiwall carbon nanotubes as an electrochemical additive for the Br 3 − /Br − redox couple, the highly energy dense (SPr) 2 V/Br − flow battery manifested outstanding current performance, up to 78% energy efficiency at 40 mA cm −2 current density and 227 mW cm −2 power density, the highest power density known for pH neutral organic flow batteries. 

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5. 3D Printing of Solution‐Processable 2D Nanoplates and 1D Nanorods for Flexible Thermoelectrics with Ultrahigh Power Factor at Low‐Medium Temperatures

   https://doi.org/10.1002/advs.201901788  

   Dun, Chaochao; Kuang, Wenzheng; Kempf, Nicholas; Saeidi‐Javash, Mortaza; Singh, David J.; Zhang, Yanliang (October 2019, Advanced Science)

   Abstract Solution‐processable semiconducting 2D nanoplates and 1D nanorods are attractive building blocks for diverse technologies, including thermoelectrics, optoelectronics, and electronics. However, transforming colloidal nanoparticles into high‐performance and flexible devices remains a challenge. For example, flexible films prepared by solution‐processed semiconducting nanocrystals are typically plagued by poor thermoelectric and electrical transport properties. Here, a highly scalable 3D conformal additive printing approach to directly convert solution‐processed 2D nanoplates and 1D nanorods into high‐performing flexible devices is reported. The flexible films printed using Sb₂Te₃nanoplates and subsequently sintered at 400 °C demonstrate exceptional thermoelectric power factor of 1.5 mW m⁻¹K⁻²over a wide temperature range (350–550 K). By synergistically combining Sb₂Te₃2D nanoplates with Te 1D nanorods, the power factor of the flexible film reaches an unprecedented maximum value of 2.2 mW m⁻¹K⁻²at 500 K, which is significantly higher than the best reported values for p‐type flexible thermoelectric films. A fully printed flexible generator device exhibits a competitive electrical power density of 7.65 mW cm⁻²with a reasonably small temperature difference of 60 K. The versatile printing method for directly transforming nanoscale building blocks into functional devices paves the way for developing not only flexible energy harvesters but also a broad range of flexible/wearable electronics and sensors. 

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