“…Besides, the operating mechanism of contact mode nanogenerators may make the sealing and packaging of the devices more difficult, which limits the application of triboelectric nanogenerators in harsh environment [25]. Otherwise, the hard substrates or large size of high-output triboelectric nanogenerators will make the devices less wearable [26,27]. Compared to triboelectric nanogenerators, piezoelectric nanogenerators have the merits of better portability and durability because piezoelectric materials are not easily damaged under the action of external forces, but their output performance is still lower than that of triboelectric nanogenerators [28][29][30].…”
For traditional piezoelectric sensors based on poled ceramics, a low curie temperature (Tc) is a fatal flaw due to the depolarization phenomenon. However, in this study, we find the low Tc would be a benefit for flexible piezoelectric sensors because small alterations of force trigger large changes in polarization. BaTi0.88Sn0.12O3 (BTS) with high piezoelectric coefficient and low Tc close to human body temperature is taken as an example for materials of this kind. Continuous piezoelectric BTS films were deposited on the flexible glass fiber fabrics (GFF), self-powered sensors based on the ultra-thin, superflexible, and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing. In the low force region (1–9 N), the sensors have the outstanding performance with voltage sensitivity of 1.23 V N−1 and current sensitivity of 41.0 nA N−1. The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops, finger joint motion, tiny surface deformation, and fatigue driving with high sensitivity. This work provides a new paradigm for the preparation of superflexible, highly sensitive and wearable self-powered piezoelectric sensors, and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation, human motion monitoring, and intelligent robot.
“…Besides, the operating mechanism of contact mode nanogenerators may make the sealing and packaging of the devices more difficult, which limits the application of triboelectric nanogenerators in harsh environment [25]. Otherwise, the hard substrates or large size of high-output triboelectric nanogenerators will make the devices less wearable [26,27]. Compared to triboelectric nanogenerators, piezoelectric nanogenerators have the merits of better portability and durability because piezoelectric materials are not easily damaged under the action of external forces, but their output performance is still lower than that of triboelectric nanogenerators [28][29][30].…”
For traditional piezoelectric sensors based on poled ceramics, a low curie temperature (Tc) is a fatal flaw due to the depolarization phenomenon. However, in this study, we find the low Tc would be a benefit for flexible piezoelectric sensors because small alterations of force trigger large changes in polarization. BaTi0.88Sn0.12O3 (BTS) with high piezoelectric coefficient and low Tc close to human body temperature is taken as an example for materials of this kind. Continuous piezoelectric BTS films were deposited on the flexible glass fiber fabrics (GFF), self-powered sensors based on the ultra-thin, superflexible, and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing. In the low force region (1–9 N), the sensors have the outstanding performance with voltage sensitivity of 1.23 V N−1 and current sensitivity of 41.0 nA N−1. The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops, finger joint motion, tiny surface deformation, and fatigue driving with high sensitivity. This work provides a new paradigm for the preparation of superflexible, highly sensitive and wearable self-powered piezoelectric sensors, and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation, human motion monitoring, and intelligent robot.
“…FTIR spectrum analysis is an analytical technique which provides information about the chemical bonds or molecular structure of a material. As shown in Figure 3 b, the FTIR spectrum confirmed the crystal content of the β-phase at wavenumbers of 470 cm −1 , 506 cm −1 , 841 cm −1 , 1070 cm −1 , 1118 cm −1 , 1166 cm −1 , 1281cm −1 , 1399 cm −1 and 1430 cm −1 , and of the α-phase at 878 cm −1 [ 44 , 45 , 46 ]. It showed a similar relationship to that in Figure 3 a, where the content of the β-phase of the polymer with added ZnO nanoparticles but etched by the acid solution later was higher than that of the polymer without ZnO nanoparticles but lower than that of the polymer with added ZnO nanoparticles.…”
Section: Fabrication and Characterizationmentioning
This research introduces an idea of producing both nanoscale and microscale pores in piezoelectric material, and combining the properties of the molecular β-phase dipoles in ferroelectric material and the space charge dipoles in order to increase the sensitivity of the sensor and modulate the response frequency bandwidth of the material. Based on this idea, a bi-nano-micro porous dual ferro-electret hybrid self-powered flexible heart sound detection sensor is proposed. Acid etching and electrospinning were the fabrication processes used to produce a piezoelectric film with nanoscale and microscale pores, and corona poling was used for air ionization to produce an electret effect. In this paper, the manufacturing process of the sensor is introduced, and the effect of the porous structure and corona poling on improving the performance of the sensor is discussed. The proposed flexible sensor has an equivalent piezoelectric coefficient d33 of 3312 pC/N, which is much larger than the piezoelectric coefficient of the common piezoelectric materials. Experiments were carried out to verify the function of the flexible sensor together with the SS17L heart sound sensor (BIOPAC, Goleta, CA, USA) as a reference. The test results demonstrated its practical application for wearable heart sound detection and the potential for heart disease detection. The proposed flexible sensor in this paper could realize batch production, and has the advantages of flexibility, low production cost and a short processing time compared with the existing heart sound detection sensors.
“…(2019) MXene Integrating the poly(vinyl alcohol) (PVA) with MXene nanosheets 117.7 V – 124,000 cycles for contact test Jiang et al. (2019) Graphene Based on polyvinylidene fluoride (PVDF) via graphene nanosheets incorporation in conjunction with electrospinning technology 1511 V 189 mA m −2 80,000 cycles for contact test Shi et al. (2021) Nanosheet-based thermoelectric generators Metal dichalcogenide (TMDC) Chemically exfoliated – – Over 100 cycles for stretch test Oh et al.…”
Section: Conclusion and Perspectivementioning
confidence: 99%
“…As a result, the MXene-based nanogenerator manifests a remarkable output voltage of 117.7 V, extremely high durability of 124,000 cycles, as well as peak power density of 1,087.6 mW m −2 , all of which enable such MXene-based nanogenerator with deep potential for applications in all kinds of wearable electronic devices. Surprisingly, reported by Shi et al., the application of graphene nanosheets and polyvinylidene fluoride (PVDF) in TENG can obtain a dramatic peak power density of ∼130.2 W m −2 and output voltage of ∼1511 V ( Shi et al., 2021 ). Figure 8 Wearable triboelectric nanogenerators based on nanosheets (i) Optical images and output as the function of voltage responses to the repeated bending/relaxation of the triboelectric nanogenerator that was attached onto the (a, b) index finger, (c, d) knuckle, and (e, f) wrist, respectively ( Lim et al., 2017a ).…”
Summary
Nowadays, wearable devices mainly exist in the form of portable accessories with various functions, connecting various kinds of terminals like mobile phones to form various wearable systems. In a wearable system, the wearable power supply device is the key component as energy dispenser for all devices. Nanosheets, a kind of two-dimensional material, which always displays a high surface-to-volume ratio and thus is lightweight and has remarkable conductive as well as electrochemical properties, have become the optimal choice for wearable power supply devices. The development and status of nanosheet-based wearable power supply devices including nanosheet-based wearable batteries, nanosheet-based wearable supercapacitors, nanosheet-based wearable self-powered energy suppliers are introduced in this article. Besides, the future opportunities and challenges of wearable devices are discussed.
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