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Abstract Triboelectric nanogenerators (TENG) are one of the most promising candidates for powering wearable and portable devices. Example TENGs have demonstrated flexibility, light weight, biocompatibility, versatility and good performance. Textiles are a potential substrate onto, or into, which wearable technology is increasingly being incorporated but supplying power remains an enduring challenge. TENGs are a potential textile based mechanical energy harvesting power supply and there has been an increasing effort to combine TENGs with fabrics. A significant challenge exists in the integration without losing the performance of the TENG or the original properties (appearance, breathability, washability, and durability) and feel of the textile. Various approaches towards the realisation of textile-based TENGs (T-TENGs) have been demonstrated. Depending on its structure, T-TENGs can be divided into two main types, fabric-based TENG and fibre-based TENG. The fabric-based TENG is composed of conventional and/or modified fabrics, which serve as a substrate and/or a triboelectric material. The fibre-based TENG is fabricated as a single fibre or a collection of interlaced fibres. This paper provides an up to date review of the progress in the research of T-TENGs. The paper covers the basic operating principles, possible operation modes, textile manufacturing methods, material selections, T-TENG fabrication process, surface modification and structural designs. Issues, such as standardised measurement parameters, the challenges and limitations of T-TENG are discussed. Graphical abstract fx1 Highlights • Reviews the recent developments in textile triboelectric nanogenerators (T-TENGs). • Discuss challenges of integrating high performance TENGs and retaining textile properties. • Classification into two main types, fabric-based TENG and fibre-based TENG. • Contact-separation mode is suitable for human motion, and gives high power output. • Highlights lack of standardisation in methods and presentation of performance data. [ABSTRACT FROM AUTHOR]

This paper details the enhancements in the dielectric and piezoelectric properties of a low-temperature screen-printable piezoelectric nano-composite film on flexible plastic and textile substrates. These enhancements involved adding silver nano particles to the nano-composite material and using an additional cold isostatic pressing (CIP) post-processing procedure. These developments have resulted in a 18% increase in the free-standing piezoelectric charge coefficient d 33 to a value of 98 pC/N. The increase in the dielectric constant of the piezoelectric film has, however, resulted in a decrease in the peak output voltage of the composite film. The potential for this material to be used to harvest mechanical energy from a variety of textiles under compressive and bending forces has been evaluated theoretically and experimentally. The maximum energy density of the enhanced piezoelectric material under 800 N compressive force was found to be 34 J/m 3 on a Kermel textile. The maximum energy density of the enhanced piezoelectric material under bending was found to be 14.3 J/m 3 on a cotton textile. These results agree very favourably with the theoretical predictions. For a 10x10 cm piezoelectric element 100 µm thick this equates to 38 μJ and 14.3 μJ of energy generated per mechanical action respectively which is a potentially useful amount of energy. [ABSTRACT FROM AUTHOR]

This study compares the energy available on the car dashboard for powering in-car wireless tags for asset tracking and parking applications. Three energy sources available on the dashboard of a vehicle were investigated, i.e. vibration energy, thermal energy and light energy. The area available for the energy harvester is the same as a credit card (85×54 mm 2 ). Simulations were carried out to estimate the potential electrical power that can be generated from the three energy sources. It was found that a vibration harvester can generate tens of μW under all weather conditions. The other two types of energy harvesters can generate tens of mW on a sunny day. However, the output power of a thermogenerator drops to 0 while the power density of a solar cell drops by up to 40% on an overcast or rainy day. [ABSTRACT FROM AUTHOR]

A planar electroluminescent (EL) lamp has been screen-printed directly on to woven polyester cotton fabric to create a smart fabric lamp. The EL lamp consists of six printed layers and has been produced in colours: light blue, dark blue, and orange. The printed structure has high durability whilst maintaining the flexible and breathable properties of the fabric. The printing process relies on an interface layer developed at the University of Southampton [1] to smooth the woven fabric surface where required, presenting a more homogenous surface than the underlying woven fabric for the subsequently printed functional layers. [ABSTRACT FROM AUTHOR]

This paper reports the design, fabrication and testing of a free-standing encastre beam resonator which is entirely fabricated using screen printing onto a flexible polyimide substrate. The fabrication of the free-standing resonator was achieved using sacrificial techniques. The resonator was designed to be excited at one end of the beam and the vibrations detected on the other end using piezoelectric material. The resonator was 11 mm long and 4 mm wide with an air gap of 119 μm, created by selectively removing the sacrificial layer. The device resonates in air with maximum generated voltage of 0.1545 volt at fundamental frequency of 3.834 kHz. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the screen printing of free-standing cantilever beams on to fabric, for use as motion detectors. Such low cost motion detectors could be used in clothing as activity monitors to indicate if the wearer is unconscious in safety critical applications, e.g. a fireman in a building. We have fabricated capacitive free-standing cantilevers by screen printing sacrificial and structural materials onto a fabric substrate. In this paper, these devices are used as motion detectors which are mounted and tested on a human forearm alongside a commercial accelerometer, for comparison. The results show the feasibility of using a fabric based cantilever to indicate that the wearer is moving. [Copyright &y& Elsevier]

Abstract: This paper studies the performance of linear Vibration Energy Harvesters (VEH) under broadband vibrations with multiple frequency peaks. The output power of both electromagnetic and piezoelectric linear VEH is determined when excited by a single frequency excitation and when excited by two frequency peaks, one at resonance and the other at a different frequency (defined as the interference frequency). Experimentally, it was found that when a linear VEH is excited by two-peak vibrations, its output power is lower than in the case of the single frequency excitation. Furthermore, the larger the amplitude at the interference frequencies, the lower the output power of the VEH. Also, for the same interference peak amplitudes, the further the interference frequency is from the resonant frequency, the lower the output power is. These results suggest that when designing a linear VEH for multiple-peak broadband vibrations, the VEH should be matched to the lowest peak frequency and that pure sinusoidal excitation should be avoided when laboratory testing VEH for use in applications with multiple frequencies. [Copyright &y& Elsevier]

Abstract: This paper studies the feasibility of increasing the output power of vibration piezoelectric energy harvesters using multilayer structures. In this study, single-layer, double-layer and triple-layer devices with the same resonant frequency were compared. Two design cases were studied-: In the first case, the overall thickness of all PZT layers is fixed and each PZT layer has the same thickness. In the second case, the thickness of one PZT layer is fixed. The output power of these generators was studied and compared for the conditions where all the PZT layers were connected in parallel and in series. In all cases, the multilayer structure increased the output power over the single layer structure in piezoelectric energy harvesting. [Copyright &y& Elsevier]

A novel textile-based triboelectric nanogenerator (TENG) with woven structure operating in freestanding triboelectric-layer mode, defined as a woven-TENG, has been developed. Whereas most woven-structured TENGs operate in contact-separation mode and consist of one type of triboelectric material, this woven-TENG comprises woven electrodes and woven strips of positive and negative triboelectric material, which form a checker-like pattern over the electrodes with matching periodicity. The implementation of the positive and negative triboelectric material significantly improves the performance of the woven-TENG. Furthermore, in contrast to the conventional grating-structured and woven-structured TENG, which are designed to operate only in one moving direction, this new design also allows the woven-TENG to harvest energy from all-planar directions of movement. The woven-TENG with woven strips of nylon and polytetrafluoroethylenevinyl (PTFE) fabric can generate a root mean square (RMS) open-circuit voltage of 62.9 V, an RMS short-circuit current of 1.77 µA and a maximum RMS power of 34.8 µW at a load resistance of 50 MΩ, a mechanical oscillation of 2 Hz and a contact force of 5 N. This corresponds to a maximum RMS power density of 5.43 mW/m2. [Display omitted] • Harvesting energy from arbitrary sliding directions. • Novel design of woven TENG with positive and negative triboelectric material. • Improvement in performance by 2.2 times compared to TENGs with single material. • Compatible with standard textile manufacturing. [ABSTRACT FROM AUTHOR]

This paper reports a novel design of textile-based triboelectric nanogenerator (TENG) with alternate grated strips of positive and negative triboelectric material operating in freestanding triboelectric-layer mode, defined as a pnG-TENG. Whereas most grating-structured TENGs operating in a freestanding triboelectric-layer mode comprise gratings of one type of triboelectric material separated by air gaps, this design presents a replacement of the air gaps by another triboelectric material with the opposite polarity to the existing triboelectric material. This is predicted to increase performance by increasing the contact area of the generator. The pnG-TENG with 10 gratings of nylon fabric and PVC heat transfer vinyl delivers an RMS open-circuit voltage of 136 V, an RMS short-circuit current of 2.68 μA and a maximum RMS power of 125 μW at a load resistance of 50 MΩ, a mechanical oscillation of 2 Hz and a contact force of 5 N. This corresponds to a maximum RMS power density of 38.8 mW/m2, which is 1.94 and 6.43 times greater than the power generated by the TENG with a single triboelectric material and the TENG with no gratings, respectively. Image 1 • Novel design of textile-based TENG with alternate grated strips. • Improvement in performance by 1.94 times compared to TENGs with single material. • Compatible with standard textile manufacturing. • Investigation of rectifier circuits including Bennet's doubler, half-wave and full-wave. [ABSTRACT FROM AUTHOR]