Xinyu Du

Effects of polymerization potential on the properties of electrosynthesized PEDOT films

Abstract Poly(3,4-ethylenedioxythiophene) (PEDOT) films were prepared from an aqueous solution by electrooxidation at different anodic potential in the range 0.8–1.5 V (vs. SCE). The effect of polymerization potential on conductivity, electrochemical behavior and ESR response of PEDOT film has been investigated. The overoxidation peak of PEDOT exists near the polymerization potential of 3,4-ethylenedioxythiophene. The overoxidation behavior of PEDOT with polymerization potential yielded bell-shaped curve of the conductivity of PEDOT and the polymerization rate with the polymerization potential. This phenomenon has been reported for the first time.

Self-Powered Electrospinning System Driven by a Triboelectric Nanogenerator

Broadening the application area of the triboelectric nanogenerators (TENGs) is one of the research emphases in the study of the TENGs, whose output characteristic is high voltage with low current. Here we design a self-powered electrospinning system, which is composed of a rotating-disk TENG (R-TENG), a voltage-doubling rectifying circuit (VDRC), and a simple spinneret. The R-TENG can generate an alternating voltage up to 1400 V. By using a voltage-doubling rectifying circuit, a maximum constant direct voltage of 8.0 kV can be obtained under the optimal configuration and is able to power the electrospinning system for fabricating various polymer nanofibers, such as polyethylene terephthalate (PET), polyamide-6 (PA6), polyacrylonitrile (PAN), polyvinylidene difluoride (PVDF), and thermoplastic polyurethanes (TPU). The system demonstrates the capability of a TENG for high-voltage applications, such as manufacturing nanofibers by electrospinning.

Ultra-robust triboelectric nanogenerator for harvesting rotary mechanical energy

Triboelectric nanogenerators (TENGs) for harvesting rotary mechanical energy are mostly based on in-plane sliding or free-standing mode. However, the relative displacement between two contacting triboelectric layers causes abrasion, which lowers the output power and reduces service life. Therefore, it is important to develop a method to minimize abrasion when harvesting rotary mechanical energy. Here, we report a scale-like structured TENG (SL-TENG), in which two triboelectric layers work under a contact-separation mode to avoid in-plane relative sliding in order to minimize abrasion. As a result, the SL-TENG exhibits outstanding robustness. For example, the output voltage of the SL-TENG does not exhibit any measurable decay although this output has been continuously generated through more than a million cycles. Moreover, at a very low rotation rate of 120 rpm, the SL-TENG can generate a maximum short-circuit current of 78 μA, delivering an instantaneous power density of 2.54 W/m2 to an external load. In relation to this, a Li-ion battery was charged using the SL-TENG. After a 30-min charging time, the battery achieved a discharge capacity of 0.1 mAh. Through a power management circuit integrated into the SL-TENG, a continuous direct current (DC) of 5 V is outputted, providing sufficient DC power for driving a radio-frequency wireless sensor and other conventional electronics.

Self-powered nanofiber-based screen-print triboelectric sensors for respiratory monitoring

Scientific and commercial advances have set high requirements for wearable electronics. However, the power supply, breathability, and mass production of wearable electronics still have many challenges that need to be overcome. In this study, a self-powered nanofiber-based triboelectric sensor (SNTS) was fabricated by batch-scale fabrication technologies using electrospinning and screen-printing for health monitoring via respiratory monitoring. Typically, an arch structural SNTS is assembled by a nanofiber membrane and a Ag nanoparticle electrode. The pile of nanofibers and the conductive network of Ag nanoparticles ensure a gas channel across the whole device. The gas permeability of the SNTS was as high as 6.16 mm/s, which has overwhelming advantages when compared with commonly used wearable devices composed of air-tight cast films. Due to the softness of the nanofiber membrane, the SNTS showed excellent electronic output performance irrespective of whether it was bent, twisted, or folded. The superior properties, such as breathability, skin-friendliness, self-power, and batch fabrication of SNTS offer huge potential for their application in healthcare monitoring and multifunctional intelligent systems.

Triboelectric‐Based Transparent Secret Code

Abstract Private and security information for personal identification requires an encrypted tool to extend communication channels between human and machine through a convenient and secure method. Here, a triboelectric‐based transparent secret code (TSC) that enables self‐powered sensing and information identification simultaneously in a rapid process method is reported. The transparent and hydrophobic TSC can be conformed to any cambered surface due to its high flexibility, which extends the application scenarios greatly. Independent of the power source, the TSC can induce obvious electric signals only by surface contact. This TSC is velocity‐dependent and capable of achieving a peak voltage of ≈4 V at a resistance load of 10 MΩ and a sliding speed of 0.1 m s−1, according to a 2 mm × 20 mm rectangular stripe. The fabricated TSC can maintain its performance after reciprocating rolling for about 5000 times. The applications of TSC as a self‐powered code device are demonstrated, and the ordered signals can be recognized through the height of the electric peaks, which can be further transferred into specific information by the processing program. The designed TSC has great potential in personal identification, commodity circulation, valuables management, and security defense applications.

Lithium-Ion Batteries: Charged by Triboelectric Nanogenerators with Pulsed Output Based on the Enhanced Cycling Stability

The triboelectric nanogenerator (TENG) has been used to store its generated energy into lithium-ion batteries (LIBs); however, the influences of its pulse current and high voltage on LIB polarization and dynamic behaviors have not been investigated yet. In this paper, it is found that LIBs based on the phase transition reaction of the lithium storage mechanism [LiFePO4 (LFP) and Li4Ti5O12 (LTO) electrodes] are more suitable for charging by TENGs. Thus, the enhanced cycling capacity, Coulombic efficiency (nearly 100% for LTO electrode), and energy storage efficiency (85.3% for the LFP-LTO electrode) are successfully achieved. Moreover, the pulse current has a positive effect on the increase of the Li-ion extraction, reducing the charge-transfer resistance ( Rct) for all studied electrodes as well (LFP, LiNi0.6Co0.2Mn0.2O2, LTO, and graphite). The excellent cyclability, high Coulombic, and energy storage efficiencies demonstrated the availability of storing pulsed energy generated by TENGs. This research has provided a promising analysis to obtain an enhanced charging methodology, which provides significant guidance for the scientific research of the LIBs.

Screen-Printed Washable Electronic Textiles as Self-Powered Touch/Gesture Tribo-Sensors for Intelligent Human–Machine Interaction

Multifunctional electronic textiles (E-textiles) with embedded electric circuits hold great application prospects for future wearable electronics. However, most E-textiles still have critical challenges, including air permeability, satisfactory washability, and mass fabrication. In this work, we fabricate a washable E-textile that addresses all of the concerns and shows its application as a self-powered triboelectric gesture textile for intelligent human-machine interfacing. Utilizing conductive carbon nanotubes (CNTs) and screen-printing technology, this kind of E-textile embraces high conductivity (0.2 kΩ/sq), high air permeability (88.2 mm/s), and can be manufactured on common fabric at large scales. Due to the advantage of the interaction between the CNTs and the fabrics, the electrode shows excellent stability under harsh mechanical deformation and even after being washed. Moreover, based on a single-electrode mode triboelectric nanogenerator and electrode pattern design, our E-textile exhibits highly sensitive touch/gesture sensing performance and has potential applications for human-machine interfacing.

High efficient detoxification of mustard gas surrogate based on nanofibrous fabric

In recent years, people pay more attention to the protection against chemical warfare agents, due to the increase in the probability of usage of these chemical warfare agents in wars or terrorist attacks. In this work, MgO nanoparticles were in-situ growth on the surface of poly(m-phenylene Isophthalamide) (PMIA) forming a flexible and breathable fabric for the detoxification of mustard gas surrogate. The as-prepared nanofibrous membrane possesses a flower-like structure of which endows not only increase the specific surface area of the composite but also prevent the agglomeration of the MgO nanoparticles. The detoxification ability of the PMIA@MgO nanofibrous fabric was demonstrated by gas chromatography-mass spectrometer (GC-MS). It is found that after 20u202fh of reaction time, 70.56% of the mustard gas surrogate have been decomposed.

Polymer nanocomposite-enabled high-performance triboelectric nanogenerator with self-healing capability

Triboelectric nanogenerators (TENG) have been proven to be effective for the collection of low-frequency vibrational energy in the environment. However, most polymer materials as friction layers are highly susceptible to mechanical damage during operation, which reduces the performance and lifetime of TENG. Herein, we report a high-performance, flexible triboelectric nanogenerator with reproducible self-healing electronic characteristics. Based on its soft and flexible polymers, the self-healing triboelectric nanogenerator (SH-TENG) can achieve a peak power of 2.5 W m−2 and triboelectric charge density of about 100 μC m−2. High-conductance Ag nanowires (AgNWs) are semi-embedded in the polymer to fabricate all-in-one friction layers and for an enhanced self-healing process. Both the output voltage and current of the healed device can reach up to about 99% of their original values even after five cutting/healing cycles. The fabricated SH-TENG has excellent stability and flexibility, which presents a significant step towards the fabrication of reliable triboelectric nanogenerators with recoverability and low maintenance costs.

Improved Triboelectric Nanogenerator Output Performance through Polymer Nanocomposites Filled with Core–shell-Structured Particles

Core-shell-structured BaTiO3-poly( tert-butyl acrylate) (P tBA) nanoparticles are successfully prepared by in situ atom transfer radical polymerization of tert-butyl acrylate ( tBA) on BaTiO3 nanoparticle surface. The thickness of the P tBA shell layer could be controlled by adjusting the feed ratio of tBA to BaTiO3. The BaTiO3-P tBA nanoparticles are introduced into poly(vinylidene fluoride) (PVDF) matrix to form a BaTiO3-P tBA/PVDF nanocomposite. The nanocomposites keep the flexibility of the PVDF matrix with enhanced dielectric constant (∼15@100 Hz) because of the high permittivity of inorganic particles and the ester functional groups in the P tBA. Furthermore, the BaTiO3-P tBA/PVDF nanocomposites demonstrate the inherent small dielectric loss of the PVDF matrix in the tested frequency range. The high electric field dielectric constant of the nanocomposite film was investigated by polarization hysteresis loops. The high electric field effective dielectric constant of the nanocomposite is 26.5 at 150 MV/m. The output current density of the nanocomposite-based triboelectric nanogenerator (TENG) is 2.1 μA/cm2, which is above 2.5 times higher than the corresponding pure PVDF-based TENG.