Self-powered Pressure Sensor Research Articles

Self-Powered Pressure Sensor Based on Flexible Permanent Magnet Material

Self-Powered Pressure Sensor Based on Flexible Permanent Magnet Material

Compact Vital-Sensing Band with Uninterrupted Power Supply for Core Body Temperature and Pulse Rate Monitoring.

Although wearable devices for continuous monitoring of vital signs have undergone significant advancements, their need for frequent recharging precludes continuous operation, potentially leading to adverse outcomes being overlooked. Additionally, the scattered locations of the sensors hamper wearability. Herein, we present a compact vital-sensing band with uninterrupted power supply designed for continuous monitoring of core body temperature (CBT) and pulse rate. The band─which comprises two sensors, a power source (i.e., a flexible thermoelectric generator (TEG) and a battery), and a flexible circuit─is worn on the forearm. The CBT is calculated by measuring the skin temperature and heat flux, while a triboelectric nanogenerator-based self-powered pressure sensor is utilized for pulse rate monitoring. The TEG is a flexible unit that converts body heat into electricity, accumulating a total energy of 314 mJ (100%). Out of this total energy, only 43.2 mJ (7.2%) is utilized for CBT measurements, while the remaining 270.80 mJ (92.8%) is stored in the battery. This enables reliable and continuous operation of the vital-sensing band, highlighting its potential for use in healthcare applications.

Templates-Built Structural Designs for Piezoelectrochemical Pressure Sensors.

Self-powered sensors, capable of detecting static and dynamic pressure without an external power source, are pivotal for advancements in human-computer interaction, health monitoring, and artificial intelligence. Current sensing technologies, however, often fall short of meeting the growing needs for precise and timely pressure monitoring. This article introduces a novel self-powered pressure sensor utilizing electrochemical reactions. The sensor's ion conduction path and internal resistance adjust in response to external stress across a broad range. Its three-dimensional structure, crafted by using a simple template on the electrolyte, enables the efficient and cost-effective detection of various mechanical stimuli. This device not only achieves an optimized power density of approximately 2.34 mW cm-2─surpassing most existing technologies─but also features excellent flexibility, quick response, and recovery times (0.15 and 0.19 s respectively); high durability (2000 cycles); and a broad sensing range (0.23-20 kPa). Moreover, it serves as an ionic touchpad, enhancing data collection and recognition, and integrates seamlessly with a mouthpiece for accurate, real-time monitoring of respiratory activities. This innovative sensor offers minimal cost and simple process requirements while providing multifunctional capabilities for energy harvesting and pressure sensing, marking a significant step forward in the design of next-generation sensors.

Effective CuO/Cu7S4 nanospheres heterostructures for advanced “rocking-chair” zinc-ion battery

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted considerable attention for energy storage owing to their environmental friendliness and high safety. However, the adverse side reactions and unsatisfactory cycle life brought by Zn-metal anodes limit their large applications. Herein, CuO/Cu7S4 (CSO) heterostructured hollow nanospheres is proposed as an attractive conversion-type Zn-metal-free anode for “rocking-chair” ZIBs. The CSO/graphite self-supporting electrode delivers a high capacity of 271 mAh/g at current density of 0.1 A/g and a superior cyclic stability of 1200 cycles. Based on the excellent electrochemical performance of CSO/graphite electrode, we have constructed a self-powered pressure sensor integrated system using the “rocking-chair” zinc ion battery as the power source, demonstrating significant practicality. This work provides a high-performance conversion type anode material for aqueous multivalent metal ion batteries.

A wearable, self-sustainable, and wireless plantar pressure and temperature monitoring system for foot ulceration prognosis and rehabilitation

Continuous foot temperature and pressure monitoring are desirable for prevention and care of foot health conditions such as Diabetic foot ulceration (DFU). However, monitoring these parameters simultaneously is complex, and mostly rely on sensors with undisrupted power supply integration. Herein, we propose high-performance self-sustainable smart footwear capable of monitoring foot pressure and temperature at various locations for real-time applications. The footwear consists of three modules of an integrated electromagnetic generator (EMG) and triboelectric (TENG) self-powered pressure sensors operated by very elastic 3D printed thermoplastic polyurethane (TPU) springs formed by stacking circular plates that allow TENG pressure sensors to be embedded within. Additionally, Laser-induced graphene (LIG) temperature sensors are used for monitoring foot temperature. The embedded EMG can deliver high output power during various activities: walking (38 mW), running (154 mW), and jumping (75 mW), sufficient to power signal processing and transmission circuitries for wireless monitoring of foot temperature and pressure. TENG-based pressure sensors and LIG temperature sensors (LTS) embedded in this design allow mapping of foot pressure (0.2 V/kPa at 1 Hz) and foot temperature (0.55 Ω °C−1) continuously. Finally, footwear was assembled successfully to demonstrate wireless self-sustainable multisensory smart footwear for monitoring foot pressure and temperature to prevent and rehabilitate diabetic foot ulcers.

Fabrication of Flexible Wearable Mechanosensors Utilizing Piezoelectric Hydrogels Mechanically Enhanced by Dipole-Dipole Interactions.

Conductive hydrogels have been increasingly employed to construct wearable mechanosensors due to their excellent mechanical flexibility close to that of soft tissues. In this work, piezoelectric hydrogels are prepared through free radical copolymerization of acrylamide (AM) and acrylonitrile (AN) and further utilized in assembling flexible wearable mechanosensors. Introduction of the polyacrylonitrile (PAN) component in the copolymers endows the hydrogels with excellent piezoelectric properties. Meanwhile, significant enhancement of mechanical properties has been accessed by forming dipole-dipole interactions, which results in a tensile strength of 0.51 MPa. Flexible wearable mechanosensors are fabricated by utilizing piezoelectric hydrogels as key signal converting materials. Self-powered piezoelectric pressure sensors are assembled with a sensitivity (S) of 0.2 V kPa-1. Additionally, resistive strain sensors (gauge factor (GF): 0.84, strain range: 0-250%) and capacitive pressure sensors (S: 0.23 kPa-1, pressure range: 0-8 kPa) are fabricated by utilizing such hydrogels. These flexible wearable mechanosensors can monitor diverse body movements such as joint bending, walking, running, and stair climbing. This work is anticipated to offer promising soft materials for efficient mechanical-to-electrical signal conversion and provides new insights into the development of various wearable mechanosensors.

Enhancing self-induced polarization of PVDF-based triboelectric film by P-doped g-C3N4 for ultrasensitive triboelectric pressure sensors

Progress in wearable energy devices has reached the point of popularity over a few decades, as reflected by the rise of numerous sensors and storage devices driven by the urgent need for Internet of Things (IoT) applications. Triboelectric sensor (TES), on the basis of triboelectric nanogenerators (TENGs), exhibits high sensitivity and stability for pressure detection. Maximizing the sensitivity of the TES hinges upon the triboelectric layer selection capable of harnessing triboelectrification and electrostatic induction. Among them, PVDF has gained attention owing to its exceptional flexibility and tribo-negativity. However, the multiphase of pristine PVDF poses challenges, limiting its potential for TES with higher sensitivity. Tackling this issue, herein, we introduced phosphorus-doped graphitic carbon nitride (PCN) into the PVDF films to achieve self-induced polarization to enhance the sensitivity of the triboelectric pressure sensor. Through a controlled annealing temperature, phosphorus atoms are incorporated into the g-C3N4 (CN) matrix, enhancing the electronegativity of PVDF/PCN composite film while inducing a polarized β crystal phase in PVDF, thereby enabling greater attraction of positive charges. Consequently, the triboelectric output with PVDF/PCN composite film exhibited a significant improvement compared to the pristine PVDF film, achieving over a 100 V increment and the ability to power more than 100 LEDs. Furthermore, for the pressure-sensing applications, the TES with flexible PVDF/PCN triboelectric film exhibits a pressure sensitivity of 1.48 V/kPa, which shows a threefold increase in sensitivity compared to the pristine PVDF film (0.51 V/kPa), suggesting their great potential in self-powered wearable pressure sensors.

Rechargeable Self-Powered pressure sensor based on Zn-ion battery with high sensitivity and Broad-Range response

Flexible pressure sensors find broad applications in electronic skin, human–computer interaction, and health monitoring. However, developing self-powered flexible sensors capable of detecting both dynamic and static pressures with high sensitivity and a wide detection range remains a significant challenge. Here, we report the design and fabrication of a new rechargeable Zn-ion battery-type flexible self-powered pressure sensor (RZIB-FPS). In the device, the anode of a flexible Zn-ion battery is designed into a sandwich configuration with a porous isolation layer in between a conductive layer decorated with polymethylmethacrylate microspheres and a flexible Zn electrode. The self-powered pressure sensing mechanism relies on the variation in output voltage resulting from the resistance change of the anode when subjected to external pressure. This RZIB-FPS exhibits an open-circuit voltage of 1.46 V, an energy density of 392 µWh cm−2, a high sensitivity (up to 42.6 mV kPa−1), a wide pressure detection range (up to 330 kPa), and excellent cycling stability (up to 12,000 cycles). Furthermore, the proposed all-in-one device design demonstrates excellent charge–discharge performance, manifesting its high integration level and potential for sensor miniaturization. This study introduces a new strategy for developing high-performance sensors for future self-powered smart wearable electronics.

Self-Powered Wearable Pressure Sensor System for Smart Healthcare Applications

Wearable sensors mark a groundbreaking advancement in the realm of health monitoring technology. However, traditional wearable devices lack comprehensive solutions for tracking sports exercise behaviors and providing feedback on rehabilitation for those undergoing home-based recovery. To bridge this gap, a self-powered triboelectric nanogenerator (TENG)-based wearable sensing system has been developed with in-house monitoring capabilities. The wearable sensor system is composed of triboelectric pressure sensors with an electro-conductive silicone sheet and patterned Ecoflex film as the contact layers. Highly sensitive TENG sensors have been successfully embedded into a bicycle saddle and human shoe insole for real-time pressure monitoring. Experimental results demonstrate that biomechanical energy, originating from both the pelvic-saddle interactions on bicycle and human gait movements, has been successfully converted into electrical energy. The generated sensor voltage remains stable under frequency variations and external environmental conditions, such as temperature and humidity variations. Utilizing distinctive information contained in individual body mass imbalances and gait characteristics, a smart healthcare monitoring system is envisioned to extract essential biomechanical insights via artificial intelligence, facilitating a pivotal role in in-house monitoring and tracking of sports rehabilitation exercises. The as-designed low-cost, highly scalable self-powered wearable sensor system offers an accessible, user-friendly point-of-care solution for gait detection and rehabilitation monitoring for individuals with various physical impairments, with considerable potential for commercialization. Figure 1

Self-powered smart pressure sensors by stimuli-responsive ion transport within layered hydrogels

Self-powered ionic sensors represent an emerging class of device capable of detecting and converting external stimuli, such as pressure and temperature, into electrical outputs without the need for an external power source. However, they often suffer from relatively low sensitivity, and their detection capability is typically limited to the magnitude of external stimulus. In this study, we present a smart pressure sensor consisting of nanowire electrodes and three-component ionic hydrogels with distinct stiffnesses and ion selectivities. Our hydrogel device effectively converts external pressure into a convective flow of cations, which are efficiently captured by the nanowire electrodes, yielding remarkable electrical outputs. In addition, upon local compression, the hydrogel device induces a convective flow that guides cations to the nearest electrode with minimal frictional force. This creates local inhomogeneous ionic distributions around the electrodes, enabling the detection of the local position and directional movements of the applied pressure without the need for additional electrical circuits. By enabling the simultaneous detection of pressure magnitude, local position, and movement, our device is capable of encoding intricate movements into distinct electrical outputs, thereby presenting a novel avenue for the development of advanced self-powered sensors with enhanced capabilities.

Development of Highly Flexible Piezoelectric PVDF-TRFE/Reduced Graphene Oxide Doped Electrospun Nano-Fibers for Self-Powered Pressure Sensor.

The demand for self-powered, flexible, and wearable electronic devices has been increasing in recent years for physiological and biomedical applications in real-time detection due to their higher flexibility and stretchability. This work fabricated a highly sensitive, self-powered wearable microdevice with Poly-Vinylidene Fluoride-Tetra Fluoroethylene (PVDF-TrFE) nano-fibers using an electrospinning technique. The dielectric response of the polymer was improved by incorporating the reduced-graphene-oxide (rGO) multi-walled carbon nano-tubes (MWCNTs) through doping. The dielectric behavior and piezoelectric effect were improved through the stretching and orientation of polymeric chains. The outermost layer was attained by chemical vapor deposition (CVD) of conductive polymer poly (3,4-ethylenedioxythiophene) to enhance the electrical conductivity and sensitivity. The hetero-structured nano-composite comprises PVDF-TrFE doped with rGO-MWCNTs over poly (3,4-ethylenedioxythiophene) (PEDOT), forming continuous self-assembly. The piezoelectric pressure sensor is capable of detecting human physiological vital signs. The pressure sensor exhibits a high-pressure sensitivity of 19.09 kPa-1, over a sensing range of 1.0 Pa to 25 kPa, and excellent cycling stability of 10,000 cycles. The study reveals that the piezoelectric pressure sensor has superior sensing performance and is capable of monitoring human vital signs, including heartbeat and wrist pulse, masticatory movement, voice recognition, and eye blinking signals. The research work demonstrates that the device could potentially eliminate metallic sensors and be used for early disease diagnosis in biomedical and personal healthcare applications.

Light-Boosting Highly Sensitive and Ultrafast Piezoelectric Sensor Based on Composite Membrane of Copper Phthalocyanine and Graphene Oxide.

Self-powered wearable pressure sensors based on flexible electronics have emerged as a new trend due to the increasing demand for intelligent and portable devices. Improvements in pressure-sensing performance, including in the output voltage, sensitivity and response time, can greatly expand their related applications; however, this remains challenging. Here, we report on a highly sensitive piezoelectric sensor with novel light-boosting pressure-sensing performance, based on a composite membrane of copper phthalocyanine (CuPC) and graphene oxide (GO) (CuPC@GO). Under light illumination, the CuPC@GO piezoelectric sensor demonstrates a remarkable increase in output voltage (381.17 mV, 50 kPa) and sensitivity (116.80 mV/kPa, <5 kPa), which are approximately twice and three times of that the sensor without light illumination, respectively. Furthermore, light exposure significantly improves the response speed of the sensor with a response time of 38.04 µs and recovery time of 58.48 µs, while maintaining excellent mechanical stability even after 2000 cycles. Density functional theory calculations reveal that increased electron transfer from graphene to CuPC can occur when the CuPC is in the excited state, which indicates that the light illumination promotes the electron excitation of CuPC, and thus brings about the high polarization of the sensor. Importantly, these sensors exhibit universal spatial non-contact adjustability, highlighting their versatility and applicability in various settings.

Enhanced self-polarization effect by tuning interfacial binding energy for self-powered flexible piezoelectric pressure sensors

Flexible pressure sensors based on PVDF and its copolymers have been extensively investigated due to their unique self-powered characteristics and high sensitivity. Herein, a new strategy of manipulation the interfacial binding energy between the organic and inorganic groups has been utilized to enhance the performance of the flexible piezoelectric pressure sensors. Four types of interfacial interactions of different binding energy have been designed in the polydopamine (PDA) decorated lead zirconate titanate (PZT) and P(VDF-TrFE) composites. The results based on first-principles calculations reveal that PDA acts as a binder between PZT and P(VDF-TrFE) due to the strong interaction between -NH2 and -CF2- dipoles. The strong interaction results in enhanced self-polarization effect and enhanced piezoelectric effect, and the improved sensitivity of the pressure sensors. The β-phase content of P(VDF-TrFE) increases from 17% to 87% when the content of PZT@PDA nanoparticles reaches 15 wt%. PZT@PDA/P(VDF-TrFE) self-powered pressure sensor (SPPS) exhibits an output voltage of 44 V and a high sensitivity of 1.38 V/kPa with no significant performance degradation during 10,000 cycles of pressure application. Moreover, the SPPS shows an excellent self-powered ability with the highest short-circuit current of 8.6 μA and the peak power density of 15 μW/cm2. The SPPS demonstrates the extraordinary sensing performance in body motion sensing and hand gesture recognition.

Self-Powered and Self-Recoverable Multimodal Force Sensors Based on Trap State and Interfacial Electron Transfer.

Multi-dimensional force sensing that combines intensity, location, area and the like could gather a wealth of information from mechanical stimuli. Developing materials with force-induced optical and electrical dual responses would provide unique opportunities to multi-dimensional force sensing, with electrical signals quantifying the force amplitude and the luminescence output providing spatial distribution of force. However, the reliance on external power supply and high-energy excitation source brings significant challenges to the applicability of multi-dimensional force sensors. Here we reported the mechanical energy-driven and sunlight-activated materials with force-induced dual responses, and investigated the underlying mechanisms of self-sustainable force sensing. Theoretical analysis and experimental data unraveled that trap-controlled luminescence and interfacial electron transfer play a major role in force-induced optical and electrical output. These materials were manufactured into pressure sensor with renewable dual-mode output for quantifying and visualization of pressures by electrical and optical output, respectively, without power supply and high-energy irradiation. The quantification of tactile sensation and stimuli localization of mice highlighted the multi-dimensional sensing ability of the sensor. Overall, this self-powered pressure sensor with multimodal output provides more modalities of force sensing, poised to change the way that intelligent devices sense with the world.

A triboelectric nanogenerator based on flexible zwitterionic ionic conductive hydrogel for running training monitoring

Recently, wearable electronic devices based on ionic conductive hydrogel have received much attention. However, the hydrogels currently reported face challenges in terms of fatigue strength and mechanical properties. Hence, we designed a flexible zwitterionic ionic conductive (F–Zn) hydrogel for the strain sensor and triboelectric nanogenerator (F-TENG). According to the results, the open-circuit voltage (Voc) of F-TENG can reach 245.54 V. The short-circuit current (Isc) and transfer charge (Qsc) of F-TENG can arrive at 9.16 µA and 81.16 nC. As the self-powered pressure sensor, two linear sensing regions of F-TENG can be observed, with sensing sensitivities of 5.9 kPa−1 and 2.05 kPa−1, respectively. In the meantime, when the F-Zn hydrogel serves as strain sensor, the Gauge Factor (GF) can arrive at 0.99. It's important to note that F-TENG can complement the static sensing of the F-Zn hydrogel strain sensor by having application value in dynamic motion sensing. Comprehensive monitoring of running movements is achievable by two sensors with different working mechanisms, paving the way for multifunctional running hydrogel sensors.

Monolithic three-dimensional hafnia-based artificial nerve system

Artificial nerve systems that mimic the tactile perception ability of human skin could be adopted in the realization of devices for a hyperconnected society, including prosthetic devices, interfaces for virtual reality, and smart sensors. The system consists of a pressure sensor, memory, and signal processing circuit, which possess the capability of generating sensory neuron-like signals. Although technological advances have been made in semiconductor-based memory and transistors over the decades, sensor technology is still relying on micro-electromechanical systems, which are hard to realize miniaturization/high-density and high-performance technology. Here, we demonstrate a monolithic three-dimensional integrated artificial nerve on the basis of ferroelectric HfxZr1-xO2 for use in the core element of neuromorphic memory and a self-powered piezoelectric pressure sensor. The morphotropic phase boundary (MPB) state of hafnia film was formed between orthorhombic and tetragonal phases for high piezoelectric performance. The MPB-based sensor was integrated with self-rectifying ferroelectric tunnel junction memory and silicon-based ring oscillator. We realized a frequency-modulated pulse-like synaptic signal with pressure detection ability over a wide range of 1–50 kPa and a good sensitivity of 0.35 mV/kPa. Also, we demonstrate the real-time frequency-modulated operation of the artificial nerve system by adjusting the functional properties of the hafnia films.

Ion gradient induced self-powered flexible pressure sensor

Various self-powered flexible pressure sensors (including piezoelectric, triboelectric and electrochemical types) have attracted great attentions and made significant progresses, but they also have some shortcomings, such as the inability to detect static pressure (piezoelectric and triboelectric types) and performance degradation (electrochemical type). Inspired by the ion gradient power generation mechanism, we propose a self-powered flexible pressure sensor based on pressure regulated ion gradient coupled with piezoresistive effect. The proposed pressure sensor is mainly composed of high humidity region (LiCl-filter paper (FP)) and low humidity region (carbon nanotubes-FP). The results show that the sensor can directly output current signal with a wide pressure range (0.1–100 kPa). Based on the output voltage and current signals and the morphology characterization, the power generation and pressure sensing mechanisms of the sensor are clarified using the ion gradient and piezoresistive effects. In addition, the sensor can be used to identify different respiratory states in combination with machine learning. This work provides a new strategy for constructing self-powered pressure sensor based on pressure regulated ion gradient strategy coupled with piezoresistive effect.

Self-Powered Biomimetic Pressure Sensor Based on Mn-Ag Electrochemical Reaction for Monitoring Rehabilitation Training of Athletes.

Self-powered pressure detection using smart wearable devices is the subject of intense research attention, which is intended to address the critical need for prolonged and uninterrupted operations. Current piezoelectric and triboelectric sensors well respond to dynamic stimuli while overlooking static stimuli. This study proposes a dual-response potentiometric pressure sensor that responds to both dynamic and static stimuli. The proposed sensor utilizes interdigital electrodes with MnO2/carbon/polyvinyl alcohol (PVA) as the cathode and conductive silver paste as the anode. The electrolyte layer incorporates a mixed hydrogel of PVA and phosphoric acid. The optimized interdigital electrodes and sandpaper-like microstructured surface of the hydrogel electrolyte contribute to enhanced performance by facilitating an increased contact area between the electrolyte and electrodes. The sensor features an open-circuit voltage of 0.927V, a short-circuit current of 6µA, a higher sensitivity of 14mV/kPa, and outstanding cycling performance (>5000 cycles). It can accurately recognize letter writing and enable capacitor charging and LED lighting. Additionally, a data acquisition and display system employing the proposed sensor, which facilitates the monitoring of athletes' rehabilitation training, and machine learning algorithms that effectively guide rehabilitation actions are presented. This study offers novel solutions for the future development of smart wearable devices.

Hybrid triboelectric-piezoelectric nanogenerator for long-term load monitoring in total knee replacements

A self-powered and durable pressure sensor for large-scale pressure detection on the knee implant would be highly advantageous for designing long-lasting and reliable knee implants as well as obtaining information about knee function after the operation. The purpose of this study is to develop a robust energy harvester that can convert wide ranges of pressure to electricity to power a load sensor inside the knee implant. To efficiently convert loads to electricity, we design a cuboid-array-structured tribo-pizoelectric nanogenerator (TPENG) in vertical contact mode inside a knee implant package. The proposed TPENG is fabricated with aluminum and cuboid-patterned silicone rubber layers. Using the cuboid-patterned silicone rubber as a dielectric and aluminum as electrodes improves performance compared with previously reported self-powered sensors. The combination of 10 wt% dopamine-modified BaTiO3 piezoelectric nanoparticles in the silicone rubber enhanced electrical stability and mechanical durability of the silicone rubber. To examine the output, the package-harvester assemblies are loaded into an MTS machine under different periodic loading. Under different cyclic loading, frequencies, and resistance loads, the harvester’s output performance is also theoretically studied and experimentally verified. The proposed cuboid-array-structured TPENG integrated into the knee implant package can generate approximately 15 μ W of apparent power under dynamic compressive loading of 2200 N magnitude. In addition, as a result of the TPENG’s materials being effectively optimized, it possesses remarkable mechanical durability and signal stability, functioning after more than 30 000 cycles under 2200 N load and producing about 300 V peak to peak. We have also presented a mathematical model and numerical results that closely capture experimental results. We have reported how the TPENG charge density varies with force. This study represents a significant advancement in a better understanding of harvesting mechanical energy for instrumented knee implants to detect a load imbalance or abnormal gait patterns.

A Triboelectric Nanogenerator-Based Wide Range Self-Powered Flexible Pressure Sensor

Self-powered flexible pressure sensors are needed in applications such as human-machine interaction. Here, we present a triboelectric nanogenerator (TENG) based self-powered flexible pressure sensor capable of operating over a wide-range of pressures (3.2 - 1176 kPa). The sensor exhibits excellent sensitivities in various regions of the pressure range, i.e., 3.16, 0.023 and 0.031 V/kPa in the low (1-10 kPa), medium-high (10-500 kPa) and ultra-high (>500 kPa) pressure regimes respectively. Stable and repeatable TENG responses are achieved for all three pressure regimes, and this is due to the way the real contact area at the TENG interface varies with contact pressure. These results highlight the potential for TENGs in a wide range of applications such as: detecting pressure in wearable devices, human-machine interface, biomedical and automotive applications. As a proof-of-concept, we have demonstrated the use of the presented device in applications such as detection of human and robot finger tapping, collection of human gait information, and detection of impact forces.