Biomechanical Energy Harvesting Research Articles

Flexible corrugated triboelectric nanogenerators for efficient biomechanical energy harvesting and human motion monitoring

The growing demand for the sustainable energy supply of portable wearable electronic devices has recently attracted much attention. The emergence of an environmentally friendly, renewable, and sustainable energy-supplying triboelectric nanogenerator (TENG) provides new potential and promising solution. However, it requires excellent structural stability and superior properties in practical applications. In this paper, a novel flexible corrugated triboelectric nanogenerator (C-TENG) with incredible elasticity, excellent durability and output performance for efficient energy harvesting and self-powered sensing has been designed and developed. For enhancement of electric performance, a study has also been carried out for investigating different structural parameters for the optimized performance of C-TENGs. The as-made C-TENGs have shown excellent and stable electric performance, outstanding mechanical durability and washing capability. The highly self-resilient structure of C-TENG enables its open-circuit voltage, short-circuit current, and power density to reach 480 V, 137 μA and 486 μW/cm2, respectively. Furthermore, the functional applications of C-TENG as smart insoles and intelligent carpets have been demonstrated. An intelligent system has also been developed to detect human motion and monitor people's stream scale on the intelligent carpet. This study proposes a new perspective for the structural design of TENGs and advanced applications in intelligent sensing.

Multi-output AC/DC triboelectric generator with dual rectification

Triboelectric generators (TEGs) are state-of-the-art powering solutions for low-power Internet of Things (IoT) devices. TEGs convert periodic mechanical vibrations into cyclic charge flow between electrodes, establishing an alternating current (AC). AC output requires rectification prior to charging any load, creating additional circuitry and power requirements. In recent years, the focus has shifted towards developing direct current (DC) generators as potential direct powering solutions. In this work, a DC–TEG is realized using a novel topology involving mechanical switching between a pair of metal contacts. This switching is implemented in vertical contact-separation mode and therefore does not involve any significant friction between the electrodes and metal contacts, overcoming the major limitation of wear and tear in conventional mechanical switching DC–TEGs. The proposed device can obtain each half-cycle rectified output across distinct electrode pairs, which is crucial for conditioning the asymmetric output of the TEGs. An AC output can be simultaneously harvested between the pair of bottom electrodes. The complementary AC–DC outputs of this device can supply power to multiple loads at a time, or coupled together to produce an enhanced output. Placing two complementary TEG pairs adjacent to each other in this topology has the advantage of reducing the ambient electric field, which is critical in improving the charge retention capability of the TEG layers. The proposed device achieves peak instantaneous power of 1.05 μW for the DC output and 1.12 μW for the AC output across a 7 MΩ resistance. The applications of the device in driving commercial electronics, harvesting biomechanical energy, and as progressive alarming system are demonstrated. Due to its simple, flexible topology and AC-DC dual output, this device has the potential for powering multiple loads and applications in diverse scenarios.

Zirconium metal-organic framework and hybridized Co-NPC@MXene nanocomposite-coated fabric for stretchable, humidity-resistant triboelectric nanogenerators and self-powered tactile sensors

High-performance triboelectric nanogenerators (TENGs) have become more attractive for energy harvesting and self-powered sensing applications. Herein, a stretchable, humidity-resistant, and high-performance multilayered TENG (M-TENG) is newly developed for self-powered biomotion and tactile sensing applications by using a zirconium metal-organic framework (MOF-525)@Ecoflex nanocomposite with a layer of Ecoflex@cobalt-nanoporous carbon (Co-NPC)@MXene. The MOF-525 improved TENG’s performance four times due to homogeneous porosity and high charge accumulation. The porous structure of the Co-NPC functions as charge traps, promoting high charge-trapping capability, while the MXene nanosheets operate as microcapacitors, improving transport-ions inside the Ecoflex@Co-NPC@MXene nanocomposite (charge-trapping and charge-transport). When the Ecoflex@Co-NPC@MXene nanocomposite was added as an intermediate layer, it captured triboelectric charges from the charge-generating layer and accumulated more negative charges, improving the M-TENG performance by 13 times. A 3D-printed microstructure is apprehended to the surface to increase contact area and humidity-resistant. Besides, knitted fabrics provide flexible electrodes due to their excellent stretchability. The as-prepared M-TENG showed excellent performance, including a power density of 25.7 W/m2, sensitivity (149 V/KPa), humidity-resistant, and stretchability (245%) which are superior to the previously reported TENGs. By exploiting the outstanding stretchability of the M-TENG and its ultra-high sensitivity to mechanical stimuli, practical applications were successfully demonstrated in low-frequency wearable biomotion monitoring, biomechanical energy harvesting, high-precision character recognition, and as a self-powered tactile sensor. Furthermore, the real-time sensing capability was demonstrated via the LabVIEW interface and virtual-reality car games control by tracing the finger. Therefore, this work is anticipated to open exciting opportunities for wearable energy harvesters, self-powered sensing systems, and human-machine interfaces.

A Review on Wearable Electrospun Polymeric Piezoelectric Sensors and Energy Harvesters

AbstractIn recent years, wearable sensors and energy harvesters have shown great potential for a wide range of applications in personalized healthcare, robotics, and human–machine interfaces. Among different types of materials used in wearable electronics, piezoelectric materials have gained enormous attention due to their exclusive ability to harvest energy from ambient sources. Piezoelectric materials can be utilized as sensing elements in wearable sensors while harvesting biomechanical energy. Electrospun piezoelectric polymer nanofibers are extensively investigated due to their high flexibility, ease of processing, biocompatibility, and higher piezoelectric property (in contrast to their corresponding cast films). However, as compared to piezoceramic materials, they mostly exhibit relatively lower piezoelectric coefficients. Therefore, considerable efforts have been devoted to improving the piezoelectricity of electrospun polymer nanofibers recently, resulting in significant advances. This review presents a broad overview of these advances including new material, structure designs as well as new strategies to enhance piezoelectricity of electrospun polymer nanofibers. The challenges in achieving high mechanical performance as well as high piezoelectricity are particularly discussed. The main motivation of this review is to examine these challenges and highlight effective approaches to achieving high‐performance piezoelectric sensors and energy harvesters for wearable technologies.

Biomechanical energy harvested wireless sensing for food storage

Biomechanical energy in food cold storage is a promising sustainable energy for realizing the self-powered wireless sensing for guaranteeing the food quality and safety by door status monitoring. This paper proposes a biomechanical energy harvested wireless sensing system for food cold storage. The system includes the biomechanical energy harvester (BEH), the micro-supercapacitor, the wireless transmitter and the wireless receiver. The biomechanical energy from the door opening and closing was harvested by the BEH with four gear sets as the speed increaser and an electromagnetic generator (EMG) as the electric generator driven by a crank. The generated electricity was then stored by a micro-supercapacitor. The wireless transmitter was powered by the micro-supercapacitor for transmitting the door status sensor data to wireless receiver by 433 MHz wireless radio frequency (RF). The wireless receiver could indicate the door status by light emitting diodes (LEDs) and also wirelessly transmit to smartphone by Bluetooth. The system could monitor the door status in real time by harvesting the biomechanical energy from door opening and closing, improve the sustainability of the wireless sensing system and guarantee the food quality and safety in food cold storage.

Biomechanical knee energy harvester: Design optimization and testing

Biomechanical energy harvesters are designed to generate electrical energy from human locomotion (e.g., walking) with minimal or no additional effort by the users. These harvesters aim to carry out the work of the muscles during phases in locomotion where the muscles are acting as brakes. Currently, many harvesters focus on the knee joint during late swing, which is only one of three phases available during the gait cycle. For the device to be successful, there is a need to consider design components such as the motor/generator and the gear ratio. These components influence the amount of electrical energy that could be harvested, metabolic power during harvesting, and more. These various components make it challenging to achieve the optimal design. This paper presents a design of a knee harvester with a direct drive that enables harvesting both in flexion and extension using optimization. Subsequently, two knee devices were built and tested using five different harvesting levels. Results show that the 30% level was the best, harvesting approximately 5 W of electricity and redacting 8 W of metabolic energy compared to walking with the device as a dead weight. Evaluation of the models used in the optimization showed a good match to the system model but less for the metabolic power model. These results could pave the way for an energy harvester that could utilize more of the negative joint power during the gait cycle while reducing metabolic effort.

Versatile self-assembled electrospun micropyramid arrays for high-performance on-skin devices with minimal sensory interference

On-skin devices that show both high performance and imperceptibility are desired for physiological information detection, individual protection, and bioenergy conversion with minimal sensory interference. Herein, versatile electrospun micropyramid arrays (EMPAs) combined with ultrathin, ultralight, gas-permeable structures are developed through a self-assembly technology based on wet heterostructured electrified jets to endow various on-skin devices with both superior performance and imperceptibility. The designable self-assembly allows structural and material optimization of EMPAs for on-skin devices applied in daytime radiative cooling, pressure sensing, and bioenergy harvesting. A temperature drop of ~4 °C is obtained via an EMPA-based radiative cooling fabric under a solar intensity of 1 kW m–2. Moreover, detection of an ultraweak fingertip pulse for health diagnosis during monitoring of natural finger manipulation over a wide frequency range is realized by an EMPA piezocapacitive-triboelectric hybrid sensor, which has high sensitivity (19 kPa−1), ultralow detection limit (0.05 Pa), and ultrafast response (≤0.8 ms). Additionally, EMPA nanogenerators with high triboelectric and piezoelectric outputs achieve reliable biomechanical energy harvesting. The flexible self-assembly of EMPAs exhibits immense potential in superb individual healthcare and excellent human-machine interaction in an interference-free and comfortable manner.

Self-sustainable intermittent deep brain stimulator

Brain-implanted stimulators are revolutionizing treatment of many neurological and psychiatric diseases, but still rely on temporary batteries for power, which require periodic replacements. Battery-free, self-sustainable deep brain stimulation (DBS) devices remain an unsolved challenge. Herein, we report a self-sustainable, battery-free, intermittent DBS system. This device is enabled by interfacing a high-performance bio-triboelectric nanogenerator (Bio-TENG) as an energy harvester with bio-supercapacitors as fast-charging energy storage units to intermittently drive a DBS pulse generator. The Bio-TENG acts as a smart breathing sensor and biomechanical energy harvester using the inhalation and exhalation motions of an inflated swine lung to charge bio-supercapacitors, which drive the pulse generator to stimulate neurons in mouse hippocampus tissues ex vivo . An intra-electrode triboelectrification strategy is used to boost the Bio-TENG power output. This sustainable intermittent power approach may provide a strategy for powering brain-machine bioelectronics. • Bio-supercap/Bio-TENG successfully harvests and stores energy from breathing lungs • The harvested energy intermittently stimulates the brain in a self-sustainable system • Intra-electrode triboelectrification is introduced to boost power Elsanadidy et al. report an implantable battery-free deep brain stimulator that relies on energy from breathing to stimulate the brain. This device harvests and stores the mechanical energy from breathing lungs and may be capable of stimulating the brain hippocampus in an intermittent fashion.

Ultrahigh‐Output Triboelectric and Electromagnetic Hybrid Generator for Self‐Powered Smart Electronics and Biomedical Applications (Adv. Energy Mater. 40/2022)

Hybrid Nanogenerators In article number 2202238, Jae Yeong Park and co-workers successfully developed ultra-high output hybridized nanogenerators based on triboelectric and electromagnetic generators to scavenge biomechanical energy and provide a self-powered system. Halbach magnet arrays improve electromagnetic generator performance by concentrating magnetic flux in the coil, while polyethylene oxide nanofibers improve triboelectric performance. The fabricated device demonstrates biomechanical energy harvesting and provides a fast-charging power source for portable electronics.

Barium titanate based paraelectric material incorporated Poly(vinylidene fluoride) for biomechanical energy harvesting and self-powered mechanosensing

Being a superior dielectric material exhibiting low loss, x = 0.4 composition of Ba1-xSrxTiO3 nanoparticles have been widely used as fillers in poly(vinylidene fluoride) (PVDF) for efficient flexible dielectric and electrical energy storage application. The mentioned composition of the material is also very attractive choice of interest to the researchers due to its ability of ferroelectric to paraelectric phase transition. Due to its paraelectric nature, Ba0.6Sr0.4TiO3 has not been used for mechanical energy harvesting application till date. Here we have used Ba0.6Sr0.4TiO3 particles as fillers in PVDF matrix for efficient mechanical energy harvesting purpose. In the present work, along with the flexible dielectric, ferroelectric and energy storage applications, the developed composite films have been explicitly used for efficient biomechanical energy harvesting, powering small electronic devices and pressure sensing. The fabricated nanogenerator successfully generated a maximum output voltage and output power density of 15 V and 6.75 μW/cm2 respectively on repeated human finger tapping. The obtained output power has been clearly explained on the basis of polar phase formation and consideration of stress concentration effect.

Biomechanical Regenerative Braking Energy Harvester: A Systematic Analysis

Regenerative braking is a well-known technology applied in electric vehicles to achieve high energy efficiency through an energy-recovery mechanism. The same concept has been applied to robotic applications, such as legged robots, lower-limb prostheses, and biomechanical energy harvesters. In particular, a biomechanical energy harvester enables humans to generate watts of power while simultaneously assisting in the braking of human joints during walking. In this study, a systematic analysis of a biomechanical regenerative braking energy harvester was conducted. First, we reviewed the design considerations of each harvester component and designed an energy-harvester prototype with high power density through a systematic design process. Subsequently, the dynamics of the designed harvester and its effect on human biomechanics were analyzed through device testing and human testing. The designed harvester demonstrated a power density of 3.3 W/kg for level-ground walking during device testing. We evaluated muscle activities and joint kinematics in versatile walking scenarios such as sloped walking. In level-ground and downhill walking, the hamstring muscle activity was assisted by the braking torque simultaneously generating 1.2 W and 0.7 W, respectively, during negative work phase. Meanwhile, we confirmed that the braking torque was generated rather in the positive work phase interfering the quadriceps muscle activity. Comparing previous knee-joint-driven biomechanical regenerative braking energy harvesters, our harvester shows relatively high power density level even with slower walking speed and without any special mechanism.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40684-022-00472-6.

GnPs/PVDF decorated thermoplastic veils to boost the triboelectric nanogenerator output performance toward highly efficient energy harvesting

Triboelectric nanogenerators (TENGs) are state-of-the-art devices that generate electricity through the coupling effect of triboelectrification and electrostatic induction by harvesting mechanical energy. This study aims to boost the electrical performance of a TENG that harvests biomechanical energy to power wearable and portable electronic devices by employing a simple and inexpensive method based on GnPs. For this purpose, I have designed and produced a vertical-contact-separation mode TENG suitable for biomechanical energy harvesting using tribonegative materials Polyvinylidene difluoride (PVDF)/ Polyetheretherketone (PEEK) veil and tribopositive materials Polyethylene oxide (PEO)/ Glass and Nylon 6.6 nanofibers. The surface of the PEEK veil is coated with a PVDF solution with excellent tribonegativity and ferroelectric polarization properties using the doctor blade technique. The electrical performance of the TENG is assessed by connecting a capacitor or various load resistors to the circuit. 3 wt% GnPs@PVDF/PEEK & Nylon 6.6 nanofibers and 3 wt% GnPs@PVDF/PEEK & PEO/Glass veil TENGs deliver output voltages of 470 V and 303 V, respectively at 75.8 MΩ load resistance. The power densities of 3 wt% GnPs@PVDF/PEEK & Nylon 6.6 nanofibers and 3 wt% GnPs@PVDF/PEEK & PEO/Glass veil TENGs at 1.1 MΩ are 7.36 W/m2 and 4.04 W/m2, respectively. Root mean square (RRMS), peak to peak height (Rpp), and arithmetic mean height (Ra) of the surface roughness of 3 wt% GnPs@PVDF/PEEK are measured to be 17.59 µm, 151.08 µm, and 13.16 µm, respectively. Parallel to increased surface roughness, the output power, and output voltage of 3 wt% GnPs@PVDF/PEEK & PEO/Glass veil TENG increase by 4 and 2.23-fold, respectively. Further GnPs embedding reduces both surface roughness and electrical performance of the TENG. I believe that GnPs@PVDF/PEEK veil material has the potential to be used to make high-performance TENGs that can power portable, wearable, and self-powered electronics.

Ultrastrong-polar polyacrylonitrile organic-inorganic architected nanogenerators with synergistic triboelectric behavior for efficient biomechanical energy harvesting and self-powered sensing

Accompanying the boom in smart wearable electronics, triboelectric nanogenerators (TENGs) as burgeoning mechanical-to-electrical harvesters have drawn expanding interest. In this study, a kind of novel flexible, high-output TENGs with PAN/FCNT as tribopositive layer and PVDF/PDMS/TiO2 as tribonegative layer have been designed and developed. For a synergistic effect, PAN and PVDF possessing strongly polar -CN and -F groups are handpicked as dielectric hosts to ensure maximum charge induction and triboelectrification. Highly conductive FCNT is introduced into the insulated PAN tribopositive layer, serving as the charge transport path to reduce surface charge loss. Additional PDMS is beneficial to strengthen the triboelectronegativity of PVDF tribonegative layer, and engaged as the charge trapping sites to diminish electro-discharge in air. TiO2 is employed as filler to build an inorganic-organic (TiO2-PVDF/PDMS) composite dielectric layer because of its triple functions of potent electron capture, high dielectric constant, and promoting the formation of electroactive β-phase PVDF. Meanwhile, the hydrogen bonds between PVDF, TiO2 with semi-crosslinked PDMS can stabilize interface and enhance friction output. Consequently, the assembled TENGs exhibit an ultra-high peak-to-peak voltage of 2088 V and a maximum output power of 7.2 W/m2, which shows promising applications in energy supplying and self-powered sensing fields.

Ultrahigh‐Output Triboelectric and Electromagnetic Hybrid Generator for Self‐Powered Smart Electronics and Biomedical Applications

AbstractBiomechanical energy harvesting shows great potential in the fields of smart electronics and biomedical Internet of Things. However, it is a significant challenge to develop a biomechanically driven energy harvester with high output power and fast charging as a sustainable power source for extended practical applications. Herein, an ultrahigh‐output triboelectric and electromagnetic hybrid generator (UHO‐TEHG) is developed to efficiently harvest biomechanical energy and provide self‐powered systems for numerous applications. The Halbach magnet array is used to concentrate additional magnetic flux in the coil and significantly enhance electromagnetic performance, while the novel poly(ethylene oxide) nanofibers enhance the triboelectric performance. Through the implementation of a mechanical spring‐mass model, and rational integration of electromagnetic and triboelectric generators, the UHO‐TEHG can provide an excellent output power of 1.02 W. Compared with existing mechanical energy harvesting devices, the fabricated device exhibits a much faster battery charging performance. Experimental results reveal remarkable performance related to biomechanical energy harvesting during walking, running, hiking, mountaineering, and self‐powered wireless human motion sensor. Real‐time charging of smartphones, smartwatches, Buds Live, and iTag via customized power management circuits is demonstrated. In addition, the fabricated UHO‐TEHG demonstrates the capability to power healthcare monitoring systems using a laser‐induced hierarchical carbon nanofiber‐based e‐tattoo sensor.

High‐Performance Biomechanical Energy Harvester Enabled by Switching Interfacial Adhesion via Hydrogen Bonding and Phase Separation (Adv. Funct. Mater. 38/2022)

Biomechanical Energy Harvesters In article number 2204304, William W. Yu, Wen Jung Li, Walid A. Daoud, and co-workers demonstrate a high-performance flexible biomechanical energy harvester by switching its interfacial adhesion via hydrogen bonding interactions and solvent evaporation induced phase separation. This wearable power source can generate a record high peak power density of 20.5 W m−2 Hz−1 under a low biomechanical input of 5 N, and can sufficiently power small electronics through harvesting regular or intermittent human motions.

High power-output and highly stretchable protein-based biomechanical energy harvester

To meet the rising demand for wearable electronics with high power demand, biomechanical energy harvester based on stretchable materials with high triboelectric charge densities are required. Soy protein (SP) represents a prospective tribopositive material; however, its application is limited due to its brittle nature. Herein, we report the doping of SP with hygroscopic CaCl2 to afford a tribolayer film with improved tribopositivity and stretchability, where Ca2+ disperses evenly in SP via electrostatic interactions. The water molecules adsorbed by CaCl2 form hydrogen bonds with SP chains and improve the charge-donating ability. The optimal SP–CaCl2-0.30 film with CaCl2-doping concentration of 0.30 mmol exhibits high resilience (elongation at break: 130 %) compared with the pristine SP film (elongation at break: 4 %). The device based on SP–CaCl2-0.30 as the positive tribolayer and Ecoflex as counterpart yields open circuit voltage, short circuit current, and short-circuit transferred charge of 130 V, 4.4 µA, and 44 nC, respectively. When the load resistance matches the device’s internal resistance, the peak transient power reaches 1125 mW/m2. Moreover, the device output is maintained even after 5000 of stretch and release cycles, and the harvested charge from the bending and release motions of the finger and elbow reach 3.5 nC and 40 nC, respectively. This study demonstrates a prospective approach toward protein-based energy harvesting with high stretchability and electrical output, showing significant potential for application in wearable electronics for biomechanical energy harvesting and relative humidity monitoring.

Magnetostrictive biomechanical energy harvester with a hybrid force amplifier

Vibrating energy harvesters, capable of converting mechanical energy into electrical energy, have attracted unprecedented interest in both academia and industry because of their great potential for harvesting energy induced by human activity and energy around the body, and to drive low-power wearable biosensors and electronics, micro-robots, and implantable biomedical devices. In this paper, based on the magnetostrictive inverse effect, we propose a magnetostrictive vibration harvester using Terfenol-D, which generates electrical energy when subjected to human movement. A hybrid force amplification frame is integrated in this harvester to amplify weak biological movements. The detailed mathematical model of the multi-stage force amplification process is established, the hybrid force amplifier is also designed in detail, and its structural dimensions are optimized. The position and form of the bias magnetic field arrangement based on the Terfenol-D harvester is systematically analyzed. The experiment shows that 4.13 V peak voltage and 426.4 mW peak power are generated when the harvester is fully compressed. The output power is 213.16 mW and 371.43 mW at an average acceleration of 2.5 g for slow walking and 4 g for jogging, respectively. The results of this study suggest that the combination of rod Terfenol-D and force amplification mechanisms can be used to design bio-vibrational energy harvester with excellent performance, which is especially suitable for self-powered wearable electronic devices.

Fully Fibrous Large-Area Tailorable Triboelectric Nanogenerator Based on Solution Blow Spinning Technology for Energy Harvesting and Self-Powered Sensing.

An all-fibrous large-area (20 × 50 cm2 ) tailorable triboelectric nanogenerator (LT-TENG) is prepared using a one-step solution blow spinning technology, which has the advantages of easy operation, scale-up in the area, and high production efficiency. The prepared LT-TENG is composed of polyvinylidene fluoride (PVDF)/MXene (Ti3 C2 Tx ) nanofibers (NFs) and conductive textile. Benefiting from the fibrous materials and large-area properties, the LT-TENG possesses the merits of good tailorability, breathability, hydrophobicity, and washability. When optimized by mixing the MXene into PVDF NFs, the LT-TENG has a preferable output and sensing property, with a detection range over 16kPa and a relatively high sensitivity of 12.33V KPa-1 . At maximum applied pressure, the voltage, current, and charge are 108V, 38µA, and 35nC, respectively. This LT-TENG can serve as a biomechanical energy harvester when used as wearable devices with an output power density of 12.6mW m-2 at an external load resistance of 500 MΩ, and it also has the ability of self-powered tactile sensing for pressure mapping and slide sensing. Thus, this LT-TENG exhibits great potential prospects in wearable devices, intelligent robots, and human-machine interaction.

Plant-based triboelectric nanogenerator for biomechanical energy harvesting

As people became more aware of environmental issues, several designs of triboelectric energy harvesters based on biocompatible and eco-friendly natural materials have been developed in recent years. This manuscript reports a plant-based green triboelectric nanogenerator using extracted leaf powder of the Rumex vesicarius plant and PET as triboelectric layers. When hand-tapped, the developed TENG generated an open-circuit voltage (Voc) of 3.86 V, and a short-circuit current (Isc) of 3.78μA, respectively. The device has the highest power density of 0.1894μW/cm 2 at load resistances of ∼20 MΩ and can directly power up one light-emitting diode. The TENG response has been tested over 1200 cycles, confirming its remarkable stability. The proposed TENG can be a promising sustainable tool to capture mechanical energy from nature and our everyday actions and thus convert it into electricity.

Superhydrophobic, Humidity-Resistant, and Flexible Triboelectric Nanogenerators for Biomechanical Energy Harvesting and Wearable Self-Powered Sensing

Superhydrophobic, Humidity-Resistant, and Flexible Triboelectric Nanogenerators for Biomechanical Energy Harvesting and Wearable Self-Powered Sensing