Triboelectric Phenomena Research Articles

Biomedical device powered by triboelectric nanogenerator

Biomedical devices play vital roles in health monitoring. Operability of these devices is hindered by their limited battery life. In vivo monitoring, diagnosis, and treatment have become challenging. The proposed Triboelectric Nanogenerator helps in overcoming the shackles of battery life. This article describes the process involved in the development of a healthcare device powered by triboelectric effect. In this work a contact-separation mode based triboelectric nanogenerator (TENG) has been used to power the device. TENG uses triboelectric phenomenon to transform mechanical energy into electrical energy. A contact-separation mode TENG operates through the interaction of two triboelectric materials. These materials act as an anode and a cathode, respectively, and develop opposite charges when brought into contact. Upon separation, the charged surfaces retain their individual charges, creating a potential difference between the materials. This difference generates an electrostatic field that drives the flow of electrons from one electrode to the other. As the electrons return, the field collapses, and the materials come back into contact, repeating the cycle. The device has been used to power a heart rate monitoring system. Experimental results demonstrate the output performance and long-term durability of the TENG device. Furthermore, future research, challenges and opportunities have been elaborated.

Piezocatalytic effect induced by Schottky junction at interface of 0.5Ba(Zr0.2Ti0.8)O3 – 0.5(Ba0.7Sr0.3)TiO3

In water remediation applications ferroelectric materials have been shown wide applicability in catalysis due to their spontaneous polarization. 0.5Ba(Zr0.2Ti0.8)O3 – 0.5(Ba0.7Sr0.3)TiO3 (BST-BZT) pellets were examined for piezocatalysis activity by electrode effect. These samples were prepared using traditional solid-state reaction and sintering process. The samples were coated with silver paste using manual brushing resulting in Schottky junction having enhanced surface polarization and dye degradation capability. X-ray diffraction, Field emission scanning electron microscopy (FE SEM), and Raman spectroscopy were performed to confirm the phase, morphology and vibrational modes of prepared samples, respectively. Further, Diffuse reflectance spectra (DRS) and X-Ray Photoelectron spectroscopy (XPS) was done to check absorbance and chemical composition. Piezocatalysis activity on electrode sample was observed under 150W and 40kHz ultrasonication. Well dried samples showed enhanced dye degradation of 68%. It could be due to additional charges developed at the interface which act as Schottky junction along with triboelectric phenomenon. This highlights the significant impact of Schottky junction in electrode effect by enhancing the piezocatalytic activity.

(Invited) Triboelectric Identification of Amino Acids

Triboelectrification necessitates a frictional interaction between two dissimilar materials, and their contact electrification is characteristically based on the polarity variance in the triboelectric series. Utilizing this fundamental advantage of the triboelectric phenomenon, different materials can be identified according to their contact electrification capability. Herein, we perform an in-depth analysis of the amino acids present in the stratum corneum of human skin, and we quantify them regarding triboelectric polarization. The principal focus of this study lies in analyzing and identifying the amino acids present in copious amounts in the stratum corneum to explain their positive behavior during the contact electrification process. Thus, we present an augmented triboelectric series of amino acids with quantified triboelectric charging polarity by scrutinizing the transfer charge, work function, and atomic percentage. Furthermore, we detect the chirality of aspartic acid as it is most susceptible to racemization with clear consequences on the human skin. We expect this study to accelerate research exploiting triboelectrification and provide valuable information on the surface properties and biological activities of these important biomolecules.

Comparison of anomalies in the VLF spectrum of the natural electromagnetic field with data from the seismometer in a landslide-affected area

The data from a permanent monitoring station, based on a sound card as an AD/DA converter and a magnetic loop antenna for continuous recording of electromagnetic field intensities in the Very Low Frequency (VLF) range, were recorded and compared with data from a seismic station based on Raspberry Pi located in a landslide-affected area. The stations operated 24/7 and were placed in a room below ground level. Correlations were observed between seismic signals in the frequency spectrum from 0.1 Hz to 10 Hz (some extending beyond 20 Hz) and anomalies in the electromagnetic field in the VLF range. These anomalies are likely associated with micro-fracturing, piezo-electromagnetic, and triboelectric phenomena within the landslide body, producing relatively weak VLF emissions and a faint seismic signal. A single-component 4.5 Hz 395 Ohm vertical Racotech RGI-20DX geophone with electronic extension to lower frequencies (< 1 Hz) was used with a sampling rate of 100 sps (samples per second). VLF emissions cover almost the entire spectrum from 6 kHz with a peak at 14 kHz to 18 kHz. The received spectrum was divided into following sections: VLF band 4 kHz – 6 kHz; 6 kHz – 8 kHz; 8 kHz – 10 kHz; 10 kHz – 12 kHz; 12 kHz – 14 kHz; 14 kHz – 16 kHz; 16 kHz – 18 kHz. Simultaneously, there were changes in these sections analysed and compared with the seismic record within the same time interval.

Triboelectric behaviour of selected zeolitic-imidazolate frameworks: exploring chemical, morphological and topological influences.

Tribo- and contact electrification remain poorly understood, baffling and discombobulating scientists for millennia. Despite the technology needed to harvest mechanical energy with triboelectric generators being incredibly rudimentary and the fact that a triboelectric output can be obtained from almost any two material combinations, research into triboelectric generator materials typically focuses on achieving the highest possible output; meanwhile, understanding trends and triboelectric behaviours of related but lower performing materials is often overlooked or not studied. Metal-organic frameworks, a class of typically highly porous and crystalline coordination polymers are excellent media to study to fill this knowledge gap. Their chemistry, topology and morphology can be individually varied while keeping other material properties constant. Here we study 5 closely related zeolitic-imidazolate type metal-organic frameworks for their triboelectric performance and behaviour by contact-separating each one with five counter materials. We elucidate the triboelectric electron transfer behaviour of each material, develop a triboelectric series and characterise the surface potential by Kelvin-probe force microscopy. From our results we draw conclusions on how the chemistry, morphology and topology affect the triboelectric output by testing and characterising our series of frameworks to help better understand triboelectric phenomena.

Construction of Triboelectric Series and Chirality Detection of Amino Acids Using Triboelectric Nanogenerator.

Triboelectrification necessitates a frictional interaction between two materials, and their contact electrification is characteristically based on the polarity variance in the triboelectric series. Utilizing this fundamental advantage of the triboelectric phenomenon, different materials can be identified according to their contact electrification capability. Herein, an in-depth analysis of the amino acids present in the stratum corneum of human skin is performed and these are quantified regarding triboelectric polarization. The principal focus of this study lies in analyzing and identifying the amino acids present in copious amounts in the stratum corneum to explain their positive behavior during the contact electrification process. Thus, an augmented triboelectric series of amino acids with quantified triboelectric charging polarity by scrutinizing the transfer charge, work function, and atomic percentage is presented. Furthermore, the chirality of aspartic acid as it is most susceptible to racemization with clear consequences on the human skin is detected. The study is expected to accelerate research exploiting triboelectrification and provide valuable information on the surface properties and biological activities of these important biomolecules.

Contact Area of Electrification Materials Relating to Triboelectric Generators: A Comparative Study

Triboelectric generators (TEGs) stemming from the triboelectric phenomena, are promising for energy harvesting due to their high output power and efficiency. Analysis of the tribo material selection for TEGs has suggested that energy generation is linked to heterogeneous and homogeneous materials found at opposite ends of the triboelectric series. Current research has identified that the triboelectric phenomenon also exists from contact between identical tribo materials with the advancement of surface modification. However, a comparison of composite and identical homogeneous TEGs has yet to be reported. For this research, organic polymer membranes Polyamide-6 (PA6) and Polytetrafluoroethylene (PTFE) were evaluated. The membranes were cut into samples of varying dimensions to build three sets of TEGs for comparison. Two identical sets of four sampled TEGs were fabricated using the same membrane (i.e., PA6-PA6 and PTFE-PTFE); in contrast to a composite set of four sampled TEGs made from the two distinct membranes (i.e., PA6-PTFE). By repeatedly sampling the TEGs in sliding mode at a speed of 0.2 m/s and with a vertical force of 9.8 N an open circuit voltage (Voc) was generated and recorded. As a result, the Voc of the identical TEGs was compared to the Voc of the composite TEG in which the tribo materials are located at opposite ends of the triboelectric series. It was also observed that the Voc increased almost linear in relation to the surface area of the TEGs; thus, suggesting that the surface area of the TEG can influence significantly the Voc to a great extent.Graphical abstract

Innovative design: Flexible conductive natural rubber electrode sheets with triboelectric generator activated by wheel rotation

Efficient consumption and clean energy management play a vital role in green energy. To be a part of this effort. Among the materials explored, flexible conductive electrodes utilizing triboelectric phenomena and unique properties of natural rubber composites have demonstrated a great potential for mechanical-to-electrical energy conversion. Fabrication process involves modifying natural rubber latex by incorporating conductive fillers such as carbon black, Ketjen black, and multiwall carbon nanotubes. The modified flexible conductive natural rubber sheets (CNRs) are then characterized for their structural and electrical properties. This structural arrangement significantly reduces the electrical resistance of the NR sheets. The incorporation of the MWCNT fillers leads to an increase in dielectric constant of CNRs. These properties are optimized via a proper design of the conductive natural rubber sheet triboelectric nanogenerator (CNRS-TENG). To enhance charge accumulation, polytetrafluoroethylene (PTFE) film is applied to the bottom surface of the CNRs. The CNRS-TENG are integrated into a wheel rotation generator setup. The output performance of the wheel rotation generator is influenced by the rotational speed as well as the arrangement of phases and segments. This work demonstrates that CNRs can be integrated with flexible electronic and other energy harvesting devices, opening possibilities for multifunctional clean energy solutions.

Glycerol Flow through a Shielded Coil Induces Aggregation and Activity Enhancement of Horseradish Peroxidase

Glycerol has found its applications as a heat-transfer fluid in heat exchangers, and as a component of functional liquids in biosensor analysis. Flowing non-aqueous fluids are known to be able to induce electromagnetic fields due to the triboelectric effect. These triboelectrically generated electromagnetic fields can affect biological macromolecules. Horseradish peroxidase (HRP) is widely employed as a convenient model object for studying how external electric, magnetic, and electromagnetic fields affect enzymes. Herein, we have studied whether the flow of glycerol in a ground-shielded cylindrical coil affects the HRP enzyme incubated at a 2 cm distance near the coil’s side. Atomic force microscopy (AFM) has been employed in order to study the effect of glycerol flow on HRP at the nanoscale. An increased aggregation of HRP on mica has been observed after the incubation of the enzyme near the coil. Moreover, the enzymatic activity of HRP has also been affected. The results reported that their application can be found in biotechnology, food technology and life sciences applications, considering the development of triboelectric generators, enzyme-based biosensors and bioreactors with surface-immobilized enzymes. Our work can also be of interest for scientists studying triboelectric phenomena, representing one more step toward understanding the mechanism of the indirect action of the flow of a dielectric liquid on biological macromolecules.

The Effect of Ambient Humidity on the Performance of a Wearable Textile Triboelectric Generator

Research on the triboelectric phenomenon and its use in so‐called triboelectric generators (TEG) has often led scientists to study the various parameters involved in the production of electricity induced by the contact and friction of textile structures. Although the use of textile materials and structures to build textile‐based TEGs is of particular interest, thanks to the advantages they can offer, however, the parameter of ambient humidity acts intensively on triboelectricity, affecting their electric power outcomes. This study investigates the performance of purely textile‐based materials used in a TEG measuring device which combines vertical and sliding modes as if they are part of a wearable garment. Six single jersey‐knitted textile samples, of identical yarn linear densities, are prepared. One material (para‐aramid) is used as the reference sample and it is paired with the rest (cotton, modal, polyester, wool, and acrylic). Consequently, five material combinations are available for measuring under various relative humidity conditions. Through these test series which reflect how a textile‐based TEG would operate under real conditions when embedded in a garment, the results reveal the big impact of ambient humidity on the triboelectric voltage outcome.

Couple stress-based flexoelectricity of frictionless contact in dielectrics

The presence of flexoelectricity in dielectric materials can affect the mechanics of contact between solid bodies, especially when viewed at the micro/nano-scale. Such an effect can also contribute significantly to contact electrification ─ a charge transfer event that takes place at the contact interface. In particular, the state of deformation and stresses in the vicinity of the contacting area can differ markedly from that anticipated from classical elastic Hertzian contact theory. In the present work, we investigate the flexoelectric effect near the contacting area of an isotropic dielectric material pressed by a frictionless rigid insulator probe, serving as a model problem to reveal the potential role of flexoelectricity in contact mechanics and electrification. The investigation is based on consistent couple stress flexoelectric theory, in which electric polarization may appear due to two-way coupling between the electric field and mean curvature vectors, even for centrosymmetric dielectric materials. To this end, we develop a new boundary element formulation to calculate the displacement, stress, electric potential, and electric displacement for two-dimensional isotropic flexoelectric contact problems. The subsequent computational mechanics investigation highlights several important characteristics of triboelectric phenomena and shows that the state of stress and polarization in contacting isotropic dielectrics is dependent on the effective length scale parameter l of couple stress elasticity and the coupling flexoelectric coefficient f.

MoS2-PVDF/PDMS based flexible hybrid piezo-triboelectric nanogenerator for harvesting mechanical energy

A green energy generating device, which can harvest the energy from ambient sources present in our surroundings to fulfill the energy needs of future technologies without polluting our surrounding are becoming more in demand. To extract electrical energy from mechanical vibrations, nanogenerators based on piezoelectric and triboelectric phenomena are being explored recently. When a piezoelectric material is used as one of the two components in the triboelectric nanogenerator, these two effects can be coupled. It is possible to further improve the output efficiency of the nanogenerator by integrating these two effects to form a hybrid nanogenerator. In this work, we have fabricated the different piezoelectric energy harvesters based on MoS2-PVDF materials by varying the weight percentage (0%, 2%, 5% and 7 wt%) of MoS2. The piezoelectric output of the PVDF was found to be increased due to the incorporation of MoS2. In comparison to bare PVDF film, the piezoelectric nanogenerator based on 7 wt% of MoS2 as filler in PVDF shows nearly 2-fold increase in output voltage from 9.4 V to 18.0 V. Further, a piezo-tribo based hybrid nanogenerator (HNG) is fabricated by integrating the MoS2-PVDF film having highest piezoelectric output with PDMS thin film as two layers required for the HNG device. It may be highlighted that the introduction of MoS2 in PVDF matrix not only enhanced the piezoelectric output which may be attributed to the intrinsic piezoelectric nature of MoS2 and enhanced β-phase crystallization, the triboelectric charge generation also gets enhanced. The enhanced hybrid output performance may be attributed to its increased dielectric property and surface roughness. The MoS2-PVDF/PDMS based HNG provides an output voltage of 35.3 V, which is 1.6 times greater than the HNG based on bare PVDF/PDMS layers. The generated output power successfully lit up 21 LED bulbs by the application of a small mechanical force generated by finger tapping and could charge a 10 μF capacitor to ∼9 V in ∼400 s. The present findings suggest that by hybridizing different device mechanism in a single device the energy harvesting performance of resulting HNG can be enhanced, making it possible to drive smart wearable electronic devices.

Flexible Bielectrode‐Based Highly Sensitive Triboelectric Motion Sensor: A Sustainable and Smart Electronic Material

The self‐powered and autonomous sensors are incredibly important in advanced engineering, especially defence science. The increasing necessity of simple and smart electronics requires to be sustainably flexible, wearable, and waterproof. Triboelectricity has been a widely used mechanism for motion sensing nowadays. Almost all devices based on triboelectricity require contact between two surfaces. Herein, a touchless triboelectric motion sensor for human motion sensing and movement monitoring is developed. The device was primarily fabricated using simple latex (cis‐1,4‐polyisoprene) structures and copper (electrode materials), which make it a very cost‐effective device for sensory applications. The device is tested with specimens of different areas and heights in motion. The maximum output of the device is noted as 12 V at a specimen height of 5 cm. Further different types of human motions are applied in front of the device to ensure low energy sensitivity using triboelectric phenomena. The lightweight smart device precisely provides significant output signals for each movement of the human body which makes the device a prospective medium for motion sensing and movement monitoring which can be applied in the fields of security, energy, and medicine.

RESEARCH OF AIR IONIZATION OF AIR IN PREMISES ON OPERATION OF COMPUTER EQUIPMENT

All known studies on the effect of computer equipment on the concentration of air ions of both signs have been used for rooms where desktop computers are operated. The expediency of conducting research using a laptop computer is substantiated. Therefore, the urgent task is to study the dynamics of the air ionic composition of the air from the operation of personal computers and identify ways to maintain this indicator at the regulatory level. It is shown that the switched on computer deionizes air, and mainly on one polarity. It is established that this is a consequence of electrification of polymer surfaces. The cause of electrification is triboelectric phenomena, including the directional movement of dry air from the CPU cooling fan. Additional electrification (and consequently - deionization of air) gives the presence of the user. Confirmation of the cause of deionization is the slow recovery of the concentration of air ions after turning on the computer to a certain neutralization of surface charges. The dependences of the change of air ion concentrations on the distance from the electric field source are established. At its intensity of about 5 kV/m with dimensions of 1.0×1.0 m, the critical distance is 1.2-1.3 m. It is recommended to carry out wet absorption for an unambiguous workplace, which provides insignificant electric fields for 1.5 hours. During the operation of many personal computers, it is advisable to neutralize surface charges with an ultrasonic humidifier-ionizer. It is emphasized that the conducted research has a separate character. This is due to the presence of specific synthetic materials It is advisable to conduct research in standard rooms for the operation of computer equipment to obtain information that can be summarized and used to develop sanitary standards for the operation of computer equipment.

KPFM Study of Flexible Ferroelectric Polymer/Water Interface for Understanding the Working Principle of Liquid–Solid Triboelectric Nanogenerator

AbstractIn the present work, the triboelectric phenomenon is explored in the ferroelectric polymer (ZnO‐PVDF film) surface when water drops fall on it. Using Kelvin probe force microscopy (KPFM), it is found that negative charges are generated on the surface of the film as the water drop comes into contact with the ZnO‐PVDF film, and the induced charges are found to stay on the surface for about 5 min. It is also observed that when subsequent water drops fall on the polymer surface, the charge remains almost constant. Based on the KPFM results, a mechanism for electricity generation in liquid–solid interface triboelectric nanogenerator (LSTENG) is proposed. An LSTENG has been fabricated using ZnO‐PVDF film, which shows an open‐circuit voltage of ≈1.3V and a short circuit current of ≈0.34 µA. The electrical characteristics of the LSTENG device agree with the proposed mechanism.

Measurement and Analysis of Triboelectric Surface Charge

Contact electrification occurs when two isolated objects come into contact. Such a phenomenon led humans to first realization of the existence of electricity. Until now, the main causes of the triboelectric charging phenomenon have generally been thought to be the transfer of electrons, ions, and materials. This article, however, is limited to electron transfer on the surface, which is regarded as a general case not limited to specific situations. The contact between two objects occurs between the two surfaces; therefore, the surface properties of the material under examination are the most important properties in triboelectric charge transfer. The surface properties may include the types of materials in contact, their energy states, the roughnesses of their surfaces, and their elastic moduli. In this regard, we introduce here the current understanding of the energy band structures involved in the different types of materials, the method of measurement, an analysis of surface charges, and related applications.

Triboelectricity and textile structures

Triboelectricity is a natural phenomenon with limited applications in the past. Wide research over the last decade introduced it mainly in energy harvesting and sensing. The use of textiles in triboelectric applications mainly focuses on the energy harvesting field. The textile fabrics as active parts of wearable triboelectric generators are promising concerning the structural simplicity and the performance of the product. The clothes are made of textile fabrics and the textile-based triboelectric generator is benefitted by the large contact areas and the continuous activation thanks to the lasting movement of the wearer. Simultaneously, the textile character of the triboelectric parts supports the flexibility, elasticity, breathability etc of the clothes, maintaining the comfort of the user. The study of the triboelectric phenomenon on textile structures gives an indication of their suitability for energy harvesting applications. The present research work investigates the influence of parameters like the contact time duration of the fabrics, the force applied upon their contact, their relative orientation and their weave as well as the material type on the efficiency of the triboelectric unit. Additionally, the lack of a standard testing method imposed the design and development of a suitable testing apparatus. It operates in the vertical contact-separation mode and it allows the testing of different samples under the same conditions or of the same sample under different conditions. Textile fabric samples were paired and tested in order to evaluate their influence on the amount of energy harvested.

Endurance Test for Evaluating the Performances of a Novel Rotating-Cylinder-Type Triboelectric Charging Device

The electric charging of granular plastics in view of their electrostatic separation is one of the major industrial applications of the triboelectric phenomenon. The granules get charged by collisions and frictions with each-others and with the walls of the tribocharging device. In electrostatic separation applications, the granules of a mixture must be sufficiently charged to be attracted by electrodes of opposite polarity for their separation by type of material. The objective of the present article is to study the endurance of a novel rotating-cylinder-type triboelectric charger for two types of granular materials (sizes between 2 and 5 mm), originating from waste electric and electronic equipment: acrylonitrile butadiene styrene (ABS) and polystyrene (PS). The charger performance was evaluated by measuring the charge per mass ratio of the granules collected at the outlet of the device. The outcome of the process depended on the rotation speed of the cylinder, as well as on the mass flow rate of product. The maximal charge to mass ratio was 5.5 nC/g for the ABS product, at a mass flow rate of 1.5 g/s, and 2.5 nC/g for the sieved PS product (particle sizes between 2 and 3 mm) at a mass flow rate of 8.2 g/s. It slightly decreased in time, due to the saturation of the tribocharging cylinder.

Ways of reducing of friction surfaces wearing by using of triboelectric phenomena

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Factors Influencing the Triboelectric Charging of Granular Plastics in a Rotating-cylinder-type Tribocharger

The electric charging of granular plastics in view of their electrostatic separation is one of the major industrial applications of the triboelectric phenomenon. The granules get charged by collisions and frictions with each-others and with the walls of the tribocharging device. In electrostatic separation applications, the granules of a mixture must be sufficiently charged to be attracted by electrodes of opposite polarity for their separation by type of material. The objective of the present work is to study the effects of three factors that influence the triboelectric charging of polycarbonate granules (size: 2 mm to 5 mm) originating from waste electric and electronic equipment in a rotating-cylinder-type device: particle residence time, cylinder inclination and its rotation speed. The performance of the triboelectric charger was evaluated by measuring the charge per mass ratio of the granules collected at the outlet of the device.