Flexible Piezoelectric Sensor Research Articles

Fluorine polyimide nanofibrous composites with outstanding piezoelectric property for human motion monitoring

The limited high-temperature resistance of conventional piezoelectric polymers remains an extremely arduous obstacle to fabricate a flexible sensor that meets the practical application in extreme environments. In this paper, the fluorine-containing polyimide (FPI) nanofiber membrane was prepared by electrospinning and further encapsulated with FPI resin into a flexible and wearable piezoelectric sensor. The influence of fluorine-containing monomer content on the mechanical properties, heat resistance, and piezoelectric properties of FPI nanofiber composite membranes was systematically investigated. The fabricated samples show outstanding thermal stability with Tg of 247℃-262℃ and Td5% of 570℃. The composite also displays a low dielectric constant (2.25–3.5) and dielectric loss (0.004–0.01), respectively. It is particularly noteworthy that the prepared fluorine-containing PI nanofiber membrane exhibits excellent piezoelectric properties. The output voltage of CPI-100 can reach up to 7 V with fast response / recovery time (16 ms / 7 ms) and exceptional durability (10,000 cycles). Moreover, the prepared CPI nanofiber composite membrane sensor can effectively detect bending and pressuresignals, which can be applied to motion and pressure monitoring. We found a new kind of substrate with outstanding piezoelectric and provided a novel strategy for developing high-temperature resistant flexible self-powered piezoelectric sensors in wearable electronics.

Arrayed multi-layer piezoelectric sensor based on electrospun P(VDF-TrFE)/ZnO with enhanced piezoelectricity

Flexible pressure sensors can maintain good pressure sensing capabilities even under arbitrary degrees of deformation, which are widely used in fields such as robotic perception, physiological signal detection and wearable electronics. Currently, piezoelectric-based flexible pressure sensors face significant limitations in terms of large-area, high-sensitivity, and high-resolution pressure detection. Targeted research efforts primarily focus on enhancing the performance of piezoelectric sensors by optimizing the properties of the sensitive layer piezoelectric material and modulating device structural design. This study introduces a novel multilayer array design for flexible composite piezoelectric sensors. A high-voltage electrospinning selective deposition process is proposed to fabricate arrayed nanofiber mats. Patterned electrospun films can be automatically patterned by patterned AgNW electrodes, which allows manual alignment of patterns for subsequent stacking. Compared to sensor based on P(VDF-TrFE) prepared under the same conditions, the sensitivity of the multi-layer P(VDF-TrFE)/ZnO sensor increased from 2.82 mV/kPa to 8.30 mV/kPa, providing an effective approach for highly sensitivity wearable devices with short response time (∼5 ms).

Multifunctional Human-Computer Interaction System Based on Deep Learning-Assisted Strain Sensing Array.

Continuous and reliable monitoring of gait is crucial for health monitoring, such as postoperative recovery of bone joint surgery and early diagnosis of disease. However, existing gait analysis systems often suffer from large volumes and the requirement of special space for setting motion capture systems, limiting their application in daily life. Here, we develop an intelligent gait monitoring and analysis prediction system based on flexible piezoelectric sensors and deep learning neural networks with high sensitivity (241.29 mV/N), quick response (66 ms loading, 87 ms recovery), and excellent stability (R2 = 0.9946). The theoretical simulations and experiments confirm that the sensor provides exceptional signal feedback, which can easily acquire accurate gait data when fitted to shoe soles. By integrating high-quality gait data with a custom-built deep learning model, the system can detect and infer human motion states in real time (the recognition accuracy reaches 94.7%). To further validate the sensor's application in real life, we constructed a flexible wearable recognition system with human-computer interaction interface and a simple operation process for long-term and continuous tracking of athletes' gait, potentially aiding personalized health management, early detection of disease, and remote medical care.

Microwave, ferroelectric and electromechanical studies of free standing blended electroactive polymer films

This study probes the enhancement of the microwave, ferroelectric and electromechanical properties of electroactive polymer (EAP) blended films made out of P(VDF-TrFE) and Nafion. Blended films are synthesized using the solution casting method, with different Nafion volume percentage (0 % to 30 %), and the phase formation is confirmed using XRD and FTIR spectroscopy. The morphological features are studied using FESEM. The reflection loss of the blended films as a function of thickness has been studied in both X and Ku band using a VNA. The contribution of reflection and absorption to the shielding effectiveness are also explored. 10 % Nafion inclusion effectively minimizes microwave reflection. The P-E hysteresis study reveals that the blended films exhibit high performance in terms of the parameters. The electromechanical coupling factor has been enhanced for 10 % Nafion inclusion. These findings suggest that the blended films have potential applications in flexible piezoelectric sensors, capacitors, memory, and microwave devices.

Enhancing cardiovascular health monitoring: Simultaneous multi-artery cardiac markers recording with flexible and bio-compatible AlN piezoelectric sensors

Continuous monitoring of cardiovascular parameters like pulse wave velocity (PWV), blood pressure wave (BPW), stiffness index (SI), reflection index (RI), mean arterial pressure (MAP), and cardio-ankle vascular index (CAVI) has significant clinical importance for the early diagnosis of cardiovascular diseases (CVDs). Standard approaches, including echocardiography, impedance cardiography, or hemodynamic monitoring, are hindered by expensive and bulky apparatus and accessibility only in specialized facilities. Moreover, noninvasive techniques like sphygmomanometry, electrocardiography, and arterial tonometry often lack accuracy due to external electrical interferences, artifacts produced by unreliable electrode contacts, misreading from placement errors, or failure in detecting transient issues and trends. Here, we report a bio-compatible, flexible, noninvasive, low-cost piezoelectric sensor for continuous and real-time cardiovascular monitoring. The sensor, utilizing a thin aluminum nitride film on a flexible Kapton substrate, is used to extract heart rate, blood pressure waves, pulse wave velocities, and cardio-ankle vascular index from four arterial pulse sites: carotid, brachial, radial, and posterior tibial arteries. This simultaneous recording, for the first time in the same experiment, allows to provide a comprehensive cardiovascular patient's health profile. In a test with a 28-year-old male subject, the sensor yielded the SI = 7.1 ± 0.2 m/s, RI = 54.4 ± 0.5 %, MAP = 86.2 ± 1.5 mmHg, CAVI = 7.8 ± 0.2, and seven PWVs from the combination of the four different arterial positions, in good agreement with the typical values reported in the literature. These findings make the proposed technology a powerful tool to facilitate personalized medical diagnosis in preventing CVDs.

Hierarchically structured hollow PVDF nanofibers for flexible piezoelectric sensor

The emergence of flexible sensors addresses the limitations of traditional detection equipment, such as large size, high cost, and inconvenient portability. These sensors have significantly advanced the development of wearable electronic devices for applications in electronic skin, energy harvesting, and energy storage. To enhance the sensitivity of flexible sensors, we developed a hierarchical polyvinylidene fluoride (PVDF) nanofiber-based piezoelectric sensor. By utilizing coaxial electrospinning, we fabricated nanofibers with hollow interiors and porous outer walls. Additionally, microstructures were constructed on the fiber membrane surface by modifying the collector’s shape. The resulting microstructured hollow PVDF nanofiber membrane exhibited high β-phase content (91.31 %), excellent flexibility (maximum strain 56.9 %), and high porosity (88.94 %). The sensor demonstrated a sensitivity of 2.7 V/N (1.08 V/kPa) and a maximum output voltage of 10.1 V, approximately three times higher than that of solid PVDF nanofibers without microstructures. Even after 14,400 cycles of impact, the sensor maintained stable output. The sensor was successfully applied to human activity monitoring and gesture recognition, showcasing its ability to monitor various human activities, respond rapidly (60.4 ms), and synchronously control a mechanical palm to perform different gestures. This work highlights the potential of hierarchically structured hollow PVDF nanofibers in advancing the performance and application scope of flexible piezoelectric sensors.

Thin, flexible hybrid-structured piezoelectric sensor array with enhanced resolution and sensitivity

Wearable piezoelectric electronics have garnered significant interest in healthcare and human-machine interfaces due to their unique ability to convert mechanical stimuli into electrical signals. However, current wearable piezoelectric sensors struggle with low spatial resolution, limited sensitivity, and insufficient mechanical flexibility. Here, we report materials and designs of a thin, flexible piezoelectric sensor array with a balanced performance that could be used for spatiotemporal pressure mapping on human skin. The device with a soft-rigid hybrid structure integrates small-pixel, highly sensitive piezoceramic thick films into a conformally adaptable format that achieves satisfactory spatial resolution (6 mm), high sensitivity (15.08 mV/kPa) and optimal flexibility (bending radius of 4.23 mm). Theoretical analysis indicates that the thickness of substrate presents a trade-off between output performance and mechanical flexibility. To demonstrate the capabilities of the device, it has been employed to monitor joint bending, human gait, and throat sounds. Furthermore, it incorporates a convolutional neural network (CNN-2D) for voice recognition, achieving an impressive accuracy of 98.18 %. These capabilities underscore the potential of the device in advanced wearable applications, offering a robust platform for real-time, high-resolution physiological monitoring.

Enhanced self-driven flexible piezoelectric nanogenerator sensor based on NaNbO3/P(VDF-TrFE) films for security applications

The self-driven flexible piezoelectric sensor has wide application prospects in areas such as health monitoring, human-machine interaction, and warning detection due to its advantages of non-toxicity and high sensitivity. In this study, a composite film of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] doped with NaNbO3 (NN) was prepared by electrospinning. The highly oriented NN particles promote the formation of P(VDF-TrFE) β phase, reaching a maximum β phase content of 91%. Under mechanical motion at a frequency of approximately 3 Hz, the piezoelectric nanogenerator (PENG) fabricated from the nanofiber membrane achieved a maximum piezoelectric output of 17.3 V and 12 V in the transverse and longitudinal piezoelectric responses, respectively. With an external load of 100 MΩ, the PENG obtained a maximum power density of 0.67 μW/cm². Additionally, the PENG sensor exhibited sensitivity to various human activities and demonstrated high sensitivity and rapid response in monitoring the status of the proposed door lock opening/closing, highlighting its enormous potential in security monitoring applications.

High sensitivity flexible piezoelectric nanogenerator based on multi‐layer piezoelectric composite fiber for human motion energy harvesting

AbstractIn this study, a piezoelectric nanogenerator (PENG) based on multilayer composite fiber had good and stable piezoelectric output performance, which could realize biomechanical energy collection and human movement monitoring. The polyvinylidene fluoride‐hexafluoryl propylene (P(VDF‐HFP)) composite fiber doped with MXene was used as a promising piezoelectric functional layer (MPFP). By electrospinning, P(VDF‐HFP) composite fiber was constructed by alternating electrospinning with polyurethane (TPU) nanofibers layer by layer. The adoption of MXene as a functional filler promoted the transformation of P(VDF‐HFP) from α to piezoelectric β‐crystal, the piezoelectric β‐crystal content of P(VDF‐HFP) increased, and the dielectric properties and polarization levels were enhanced. At the same time, the multi‐layer structure design improved the piezoelectric sensitivity and mechanical properties of the composite fiber, and the composite fiber was more flexible and had longer tensile strain. With excellent dielectric and mechanical properties, 3MPFP/TPU/3MPFP/TPU multilayer composite fibers showed piezoelectric sensitivity of 10.88 V/kPa. Under the action of palm pressing, the PENG generated an open circuit voltage of 25 V, and the voltage signal of the device under different motion forms had specific characteristics such as peak value, frequency, and shape, which could be used to realize the analysis of human motion forms. This study provided an efficient, simple, and creative new idea for the application of flexible energy storage electronic devices, PENGs, and piezoelectric sensors.

Large Enhancement on Performance of Flexible Cellulose‐Based Piezoelectric Composite Film by Welding CNF and MXene via Growing ZnO to Construct a “Brick‐Rebar‐Mortar” Structure

AbstractCellulose‐based piezoelectric composites have attracted extensive attention in recent years due to their low cost, easy molding, high flexibility, and biocompatibility in the manufacture of piezoelectric nanogenerators (PENG) and sensors. In this work, cellulose nanofibril (CNF)/MXene@ZnO (CM@ZnO) piezoelectric composite films with “brick‐rebar‐mortar” structure are prepared by growing ZnO on the mixed substrate via a high‐efficiency two‐step hydrothermal method. As a hard bridge, ZnO welds CNF and MXene together to construct the “brick‐rebar‐mortar” structure, which greatly improves the piezoelectric performance. Its tensile strength reaches 65.13 ± 3.61 MPa, as well as that the longitudinal piezoelectric constant (d33) attains 14.3 ± 1.3 pC N−1. Under the force of 300 KPa, the open‐circuit voltage (VOC) and short‐circuit current (ISC) of CM@ZnO PENG are as high as 17.15 V and 997 nA, respectively. Under the force of 100 KPa, it can charge a 1.0 µF commercial capacitor to 6.07 V in 400 s. The assembled flexible piezoelectric sensor can accurately collect the pressure or vibration signal caused by bending the wrist (0.59 V) with excellent sensitivity. The performance demonstrates the feasibility of its application in wearable smart devices and provides a reference for new cellulose‐based PENGs.

Flexible Piezoelectric Sensor With a Sandwich Structure Composed of Ionic Conductive Hydrogel and PVDF Film

Flexible Piezoelectric Sensor With a Sandwich Structure Composed of Ionic Conductive Hydrogel and PVDF Film

Effect of Nanostructure Morphology and Concentration on the Piezoelectric Performance of Flexible Pressure Sensor based on PVDFTrFE/ Nano-ZnO Composite Thin Film

Background: The development of high-performance piezoelectric pressure sensors with outstanding sensitivity, good linearity, flexibility, durability, and biocompatibility is of great significance for smart robotics, human healthcare devices, smart sensors, and electronic skin. Thus, considerable progress has been achieved in enhancing the piezoelectric property of PVDF-TrFEbased composite pressure sensors by adding various ZnO nanostructures in PVDF-TrFE polymer acting as a nucleating agent and dielectric material. Aims: In this work, flexible pressure sensors with a sandwich structure based on PVDFTrFE/ nano-ZnO composite sensing film were fabricated using a simple spin-coating method and post-annealing process, while electrospinning and high-voltage polarization processes were not adopted. Methods: Poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)/nano-ZnO composite films were prepared via spin coating to fabricate flexible piezoelectric pressure sensors. ZnO nanoparticles (ZnO NPs), tetrapod ZnO (T-ZnO) and ZnO nanorods (ZnO NRs) were used as nano-fillers for piezoelectric PVDF-TrFE, to enhance the beta-crystal ratio as well as the crystallinity of PVDF-TrFE. The structural and surface morphologies of the composite films were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results: Among three different types of ZnO nanostructures with a concentration range (0-7.5 wt%), the sensor with 0.75 wt% ZnO NRs nanofiller exhibits a maximum output voltage of 1.73 V under an external pressure of 3 N and a maximum sensitivity of 586.3 mV/N at the range of 0-3 N. Further, the sensor can generate a clear piezoelectric voltage under bending and twisting deformation as well as compression and tensile deformation. Conclusion: To summarize, the addition of different concentrations of nano-ZnO can remarkably improve the piezoelectric performance of the composite sensor, and ZnO NRs can achieve better piezoelectric properties of the sensor as compared to ZnO NPs and T-ZnO. In addition, the sensor with 0.75 wt% ZnO NRs as nanofiller has the highest piezoelectric response, which is about 2.4 times that of the pure PVDF-TrFE sensor. It is demonstrated that the sensor has great potential applications in wearable health monitoring systems and mechanical stress measurement electronics.

Development of flexible multi-phase barium titanate piezoelectric sensor for physiological health and action behavior monitoring

Self-powered wearable piezoelectric sensing devices demand flexibility and high voltage electrical properties to meet personalized health and safety management needs. Aiming at the characteristics of piezoceramics with high piezoelectricity and low flexibility, this study designs a high-performance piezoelectric sensor based on multi-phase barium titanate (BTO) flexible piezoceramic film, namely multi-phase BTO sensor. The substrate-less self-supported multi-phase BTO films had excellent flexibility and could be bent 180° at a thickness of 33 μm, and exhibited good bending fatigue resistance in 1 × 10 4 bending cycles at a thickness of 5 μm. The prepared multi-phase BTO sensor could maintain good piezoelectric stability after 1.2 × 10 4 piezoelectric cycle tests. Based on the flexibility, high piezoelectricity, wearability, portability and battery-free self-powered characteristics of this sensor, the developed smart mask could monitor the respiratory signals of different frequencies and amplitudes in real time. In addition, by mounting the sensor on the hand or shoulder, different gestures and arm movements could also be detected. In summary, the multi-phase BTO sensor developed in this paper is expected to develop convenient and efficient wearable sensing devices for physiological health and behavioral activity monitoring applications.

Design and application research of a flexible array plantar sensor based on P(VDF-TrFE)/SnO2NPS/GR for Parkinson’s disease diagnosis

ABSTRACT This paper introduces a flexible array Plantar sensor fabricated through the high-voltage electrospinning process of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ，incorporating stannic oxide nanoparticles （SnO2NPS）and graphene (GR) composite nanofilm. The surface morphology, β-phase crystal content, piezoelectric performance, composition, and structure of the composite piezoelectric films were evaluated using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and a vibration platform. Experimental findings reveal that P(VDF-TrFE)/SnO2NPS/GR composite films containing 5% SnO2NPS and 0.1% GR exhibit superior open-circuit voltage and short-circuit current, measuring 22.43 V and 12.95 uA, respectively. These values are approximately 1.59 times and 1.34 times higher than those of the 5% P(VDF-TrFE) composite film and about 2.37 and 2.16 times higher than those of pure P(VDF-TrFE). A flexible piezoelectric sensor was fabricated using this composite film, and the mechanical properties and electrical impedance behavior of the sensor were investigated and analyzed.A multi-channel foot pressure collection and classification system was established based on this sensor, and a Parkinson’s disease machine learning model for multi-channel foot pressure collection was investigated. Various machine learning models for Parkinson’s disease were compared, and a fine K Nearest Neighbors（KNN） Parkinson’s disease classification model with an accuracy of 97.1% was proposed. This offers a novel solution for Parkinson’s disease diagnosis and holds significant reference value.

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.

Flexible piezoelectric pressure sensor based on BaTiO3-CNT/RTV composite film with filter paper microstructures for monitoring hand motions

Flexible piezoelectric sensors are widely used in various applications such as physiological signal monitoring and human-computer interaction. The present study introduces a BaTiO3-CNT/RTV piezoelectric sensor fabricated using a filter paper template. It incorporates micro-scale fiber stacking and a 1% CNT doping in the microstructure, resulting in a notable enhancement of sensor sensitivity, increasing it from 0.07 V N−1 to 0.69 V N−1, representing an almost tenfold improvement. Furthermore, the study investigates the influence of affecting factors like the flexible substrate of the sensing film, thickness, and mass fractions of various materials on the output voltage. The sensor exhibits superior characteristics such as good repeatability under 5000 cyclic loads, high elongation at break, fast response (80 ms) and recovery times (90 ms), and good linearity. It also demonstrates outstanding sensitivity (12 mV/10°) when monitoring different finger bending states, enabling real-time, sensitive, and reliable hand motion tracking. This sensor holds promising prospects for future developments in the fields of intelligent grasping and sign language translation.

High performance multifunctional piezoelectric PAN/UiO-66-NO2/MXene composite nanofibers for flexible touch sensor

In this study, a flexible piezoelectric sensor based on polyacrylonitrile (PAN), zirconium-based MOF (UiO-66) with nitro (NO2) and two-dimensional material MXene composite nanofiber film was proposed. When pressure was applied, the three-dimensional structural nanopores were compressed, increasing the intercalation structure between the MXene nanosheets coated in the fibers. The double-packed system produced a higher resistance change under the same pressure load, which can be explained by the fact that the low-conductivity octahedral UiO-66-NO2 particles acted as a similar “buffer” between the highly conductive MXene. At the same time, a large number of hydrogen bonds between the surfaces of the two fillers enhanced the synergistic effect and promoted the interfacial coupling effect, so that more 31-helical conformation in the PAN matrix was converted into a planar zigzag conformation. This improved the piezoelectric performance and enabled the sensor to have a voltage output of about 200 V in the detection range. And because the polyhedral form of UiO-66-NO2 particles provided a rougher surface structure, the piezoelectric sensor can achieve a high sensitivity of 5.62 V/N. The other results showed that the dielectric constant of the designed flexible piezoelectric sensor was increased to 2.67, the dielectric loss was kept at a low level of 0.026, and the maximum elongation was 56.03 %. This multi-functional sensor shows great potential in the fields of health and medical treatment, human-computer interaction, etc.

Soft-metal bonding-enabled recyclable and anti-interference flexible multilayer piezoelectric sensor for tractor tire strain monitoring

Real-time efficient sensing of machine-soil interactions, especially precise tire-ground contact information, plays a critical role in cultivation, seeding, and harvesting for smart agriculture. However, the complicated agricultural environment poses a considerable challenge to traditional rigid sensors, which cannot suffer from both large deformation and electromagnetic interference. Here, we report a novel soft-metal BiInSn bonding-enabled recyclable and anti-interference flexible multilayer piezoelectric sensor for monitoring tractor tire strain. The printed BiInSn-ink electrode fully wraps the surface fibers of porous BaTiO3/PVDF-HFP electrospun films only through a low pressure at low temperature due to its unique thermal-softening effects, which of the adhesion strength is superior to the intrinsic tension limit of the film. The compact multilayer piezoelectric sensor is thus easily prepared, remarkably increasing the output voltage compared to a single-layer case (up to 300% for three layers). Benefiting from the low melting point of the BiInSn alloy, the sensors are easily recyclable compared to conventional metal electrodes prepared with copper, silver, and gold. In addition, its high electrical conductivity also enables the shielding layer to achieve ultrahigh shielding effectiveness of 2100 dB mm−1. This sensor can be demonstrated for tire strain sensing under complex operating conditions such as plowing, harrowing, and fertilizer application. These findings serve as a foundation for accelerating the development of smart agriculture.

A BaTiO3@polyacrylonitrile/poly(vinylidene fluoride) nanofibrous composite membrane with high piezoelectricity based on the central combination design method and cross-electrospinning technology

The rapid development of piezoelectric sensors has been studied extensively, owing to their good flexibility, wearability, high sensitivity and low cost. However, some inorganic materials with good piezoelectricity cannot make sensors flexible, and the organic materials with good flexibility have a weak output electrical signal and low strength. In order to explore and optimize the preparation technology of piezoelectric sensors, a BaTiO3@polyacrylonitrile (PAN)/poly(vinylidene fluoride) (PVDF) nanofibrous composite membrane (NCM) was prepared by cross-electrospinning technology and the central combination design (CCD) method. The morphology, structure, hydrophobicity, mechanical properties and piezoelectricity of the BaTiO3@PAN/PVDF NCMs were investigated. The BaTiO3@PAN/PVDF NCMs had the better hydrophobicity and mechanical properties compared with the pure PAN/PVDF NCM. The 5BaTiO3@PAN/PVDF NCM designed by CCD had a more uniform fiber diameter, and a more stable output voltage with a 46% improvement. With the help of cross-electrospinning technology and the CCD method, the NCM will be outstanding for the development of fabricating flexible wearable piezoelectric sensors.

Sweat permeable and ultrahigh strength 3D PVDF piezoelectric nanoyarn fabric strain sensor

Commercial wearable piezoelectric sensors possess excellent anti-interference stability due to their electronic packaging. However, this packaging renders them barely breathable and compromises human comfort. To address this issue, we develop a PVDF piezoelectric nanoyarns with an ultrahigh strength of 313.3 MPa, weaving them with different yarns to form three-dimensional piezoelectric fabric (3DPF) sensor using the advanced 3D textile technology. The tensile strength (46.0 MPa) of 3DPF exhibits the highest among the reported flexible piezoelectric sensors. The 3DPF features anti-gravity unidirectional liquid transport that allows sweat to move from the inner layer near to the skin to the outer layer in 4 s, resulting in a comfortable and dry environment for the user. It should be noted that sweating does not weaken the piezoelectric properties of 3DPF, but rather enhances. Additionally, the durability and comfortability of 3DPF are similar to those of the commercial cotton T-shirts. This work provides a strategy for developing comfortable flexible wearable electronic devices.