Human Interactive Triboelectric Nanogenerator as a Self-Powered Smart Seat

Piezoelectricity, Pyroelectricity, and Ferroelectricity in Biomaterials and Biomedical Applications

Piezoelectric, pyroelectric, and ferroelectric materials are considered unique biomedical materials due to their dielectric crystals and asymmetric centers that allow them to directly convert various primary forms of energy in the environment, such as sunlight, mechanical energy, and thermal energy, into secondary energy, such as electricity and chemical energy. These materials possess exceptional energy conversion ability and excellent catalytic properties, which have led to their widespread usage within biomedical fields. Numerous biomedical applications have demonstrated great potential with these materials, including disease treatment, biosensors, and tissue engineering. For example, piezoelectric materials are used to stimulate cell growth in bone regeneration, while pyroelectric materials are applied in skin cancer detection and imaging. Ferroelectric materials have even found use in neural implants that record and stimulate electrical activity in the brain. This paper reviews the relationship between ferroelectric, piezoelectric, and pyroelectric effects and the fundamental principles of different catalytic reactions. It also highlights the preparation methods of these three materials and the significant progress made in their biomedical applications. The review concludes by presenting key challenges and future prospects for efficient catalysts based on piezoelectric, pyroelectric, and ferroelectric nanomaterials for biomedical applications.

Reclaiming Power Potential from Low Temperature Waste Heat by Thermomagnetic Heat Engines

Thermomagnetic heat engines were designed, constructed, and tested, where numbers of gadolinium (Gd) blocks were used to exploit low temperature waste heat. Gadolinium is a rare earth material whose magnetic property changes with temperature, altering between ferromagnetic and paramagnetic. A motion develops in the thermomagnetic heat engine as Gd blocks are exposed to different temperatures causing changes in their magnetic property. A change in the magnetic property of any Gd block is directly related to the resultant torque driving the thermomagnetic heat engine for power production. Among heat engines studied to date, the cylindrical thermomagnetic heat engine was able to develop a maximum mechanical power of 1.1 W at a temperature difference of 45 °C between hot and cold thermal resources. Furthermore, depending on the effectiveness of an electromagnetic generator (EMG) combined with a triboelectric nanogenerator (TENG), the electric power output can be notably improved.

Applications of Nanotechnology in Smart Textile Industry: A Critical Review

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Current trends of using nanotechnology in textile industries.

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Nanotechnology-driven techniques for fabrication and modification of textile fibers.

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Wearable nanotechnology for energy storage, sensing, drug release, optics, electronics and photonics.

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Environmental concerns associated with nanotechnology processed textiles.

Background

In recent years, nanotechnology has been playing an important role in designing smart fabrics. Nanomaterials have been employed to introduce in a sustainable manner, antimicrobial, ultraviolet resistant, electrically conductive, optical, hydrophobic and flame-retardant properties into textiles and garments. Nanomaterial based smart devices are now also being integrated with the textiles so as to perform various functions such as energy harvesting and storage, sensing, drug release and optics. These advancements have found wide applications in the fashion industry and are being developed for wider use in defence, healthcare and on-body energy harnessing applications.

Aim of review

The objective of this work is to provide an insight into the current trends of using nanotechnology in the modern textile industries and to inspire and anticipate further research in this field. This review provides an overview of the most current advances concerning on-body electronics research and the wonders which could be realized by nanomaterials in modern textiles in terms of total energy reliance on our clothes.

Key scientific concepts of review

The work underlines the various methods and techniques for the functionalization of nanomaterials and their integration into textiles with an emphasis on cost-effectiveness, comfort, wearability, energy conversion efficiency and eco-sustainability. The most recent trends of developing various nanogenerators, supercapacitors and photoelectronic devices on the fabric are highlighted, with special emphasis on the efficiency and wearability of the textile. The potential nanotoxicity associated with the processed textiles due to the tendency of these nanomaterials to leach into the environment along with possible remediation measures are also discussed. Finally, the future outlook regarding progress in the integration of smart nano-devices on textile fabrics is provided.

Tuning the Dielectric Constant and Surface Engineering of a BaTiO3/Porous PDMS Composite Film for Enhanced Triboelectric Nanogenerator Output Performance

In this work, synergistic effects derived from surface engineering and dielectric property tuning were exploited to enhance the output performance of a triboelectric nanogenerator (TENG) based on an inorganic/porous PDMS composite in a contact-separation mode. BaTiO3 (BT)/porous PDMS films with different BT weight ratios were fabricated and evaluated for triboelectric nanogenerator (TENG) application. Maximum output signals of ca. 2500 V, 150 μA, and a power density of 1.2 W m-2 are achieved from the TENG containing 7 wt % BT, which is the best compromise in terms of surface roughness, dielectric constant, and surface contact area as evidenced by SEM and AFM studies. These electrical signals are 2 times higher than those observed for the TENG without BT. The 7BT/porous PDMS-based TENG also shows high stability without a significant loss of output voltage for at least 24 000 cycles. With this optimized TENG, more than 350 LEDs are lit up and a wireless transmitter is operated within 9 s. This work not only shows the promoting effects from porous surfaces and an optimized dielectric constant but also offers a rapid and template/waste-free fabrication process for porous PDMS composite films toward large-scale production.

PDMS Microfabrication and Design for Microfluidics and Sustainable Energy Application: Review

The polydimethylsiloxane (PDMS) is popular for wide application in various fields of microfluidics, microneedles, biology, medicine, chemistry, optics, electronics, architecture, and emerging sustainable energy due to the intrinsic non-toxic, transparent, flexible, stretchable, biocompatible, hydrophobic, insulating, and negative triboelectric properties that meet different requirements. For example, the flexibility, biocompatibility, non-toxicity, good stability, and high transparency make PDMS a good candidate for the material selection of microfluidics, microneedles, biomedical, and chemistry microchips as well as for optical examination and wearable electronics. However, the hydrophobic surface and post-surface-treatment hydrophobic recovery impede the development of self-driven capillary microchips. How to develop a long-term hydrophilicity treatment for PDMS is crucial for capillary-driven microfluidics-based application. The dual-tone PDMS-to-PDMS casting for concave-and-convex microstructure without stiction is important for simplifying the process integration. The emerging triboelectric nanogenerator (TENG) uses the transparent flexible PDMS as the high negative triboelectric material to make friction with metals or other positive-triboelectric material for harvesting sustainably mechanical energy. The morphology of PDMS is related to TENG performance. This review will address the above issues in terms of PDMS microfabrication and design for the efficient micromixer, microreactor, capillary pump, microneedles, and TENG for more practical applications in the future.

A Robust and Wearable Triboelectric Tactile Patch as Intelligent Human-Machine Interface

The human-machine interface plays an important role in the diversified interactions between humans and machines, especially by swaping information exchange between human and machine operations. Considering the high wearable compatibility and self-powered capability, triboelectric-based interfaces have attracted increasing attention. Herein, this work developed a minimalist and stable interacting patch with the function of sensing and robot controlling based on triboelectric nanogenerator. This robust and wearable patch is composed of several flexible materials, namely polytetrafluoroethylene (PTFE), nylon, hydrogels electrode, and silicone rubber substrate. A signal-processing circuit was used in this patch to convert the sensor signal into a more stable signal (the deviation within 0.1 V), which provides a more effective method for sensing and robot control in a wireless way. Thus, the device can be used to control the movement of robots in real-time and exhibits a good stable performance. A specific algorithm was used in this patch to convert the 1D serial number into a 2D coordinate system, so that the click of the finger can be converted into a sliding track, so as to achieve the trajectory generation of a robot in a wireless way. It is believed that the device-based human-machine interaction with minimalist design has great potential in applications for contact perception, 2D control, robotics, and wearable electronics.

Comprehensive Review on Triboelectric Nanogenerator Based Wrist Pulse Measurement: Sensor Fabrication and Diagnosis of Arterial Pressure

As the world is marching into the era of the Internet of things (IoTs) and artificial intelligence (AI), the most vital requirement for reliable hardware development is an ultrafast response time and no performance degradation. As a reliable indicator of human physiological health, blood pressure measurement is vital in humans' daily lives, which creates a huge demand in monitoring and diagnosing blood pressure problems. The triboelectric nanogenerator (TENG) is one of the best energy devices and healthcare applications in the new era since triboelectrification is a universal and ubiquitous effect with an abundant choice of materials. TENG is reliable in physiological monitoring applications and has many benefits, including being inexpensive, easy to manufacture, and lightweight, having self-powered properties, and being available in a wide range of materials. In this review, triboelectric nanogenerator based wrist pulse measurement was summarized for blood pressure monitoring and diagnosis applications. As per the Ayurveda, imbalance in three essential components of the wrist pulse implies the human health status and reveals symptoms for diseases. The design of different TENG-based blood pressure sensors, sensing mechanisms, performance, merits, and demerits of each method are discussed.

Research on the Potential of Spherical Triboelectric Nanogenerator for Collecting Vibration Energy and Measuring Vibration

The traditional downhole drilling vibration measurement methods which use cable or battery as power supplies increase the drilling costs and reduce the drilling efficiency. This paper proposes a spherical triboelectric nanogenerator, which shows the potential to collect the downhole vibration energy and measure the vibration frequency in a self-powered model. The power generation tests show that the output signal amplitude of the spherical triboelectric nanogenerator increases as the vibration frequency increases, and it can reach a maximum output voltage of 70 V, a maximum current of 3.3 × 10⁻⁵ A, and a maximum power of 10.9 × 10⁻⁹ W at 8 Hz when a 10-ohm resistor is connected. Therefore, if the power generation is stored for a certain period of time when numbers of the spherical triboelectric nanogenerators are connected in parallel, it may provide intermittent power for the low-power downhole measurement instruments. In addition, the sensing tests show that the measurement range is 0 to 8 Hz, the test error is less than 2%, the applicable working environment temperature is below 100 degrees Celsius, and the installation distance between the spherical triboelectric nanogenerator and the vibration source should be less than the critical value of 150 cm because the output signal amplitude is inversely proportional to the distance.

Surface-Conformal Triboelectric Nanopores via Supramolecular Ternary Polymer Assembly

A triboelectric nanogenerator (TENG) is of tremendous interest owing to its high energy efficiency with a simple device architecture and applicability to various materials. Most previous topological surface modifications introduced for further improving the performance of a TENG are detrimental because they require expensive and/or harsh (e.g., high temperature and acidity) postetching processes, which limit the material choice and design of its components. Herein, we demonstrate an one-step route for developing rapid wet-processable surface-conformal triboelectric nanoporous films (STENFs). Our method is based on a simple supramolecular assembly of a ternary polymer blend suitable for various conventional solution processes such as spin-, bar-, spray-, and dip-coating. The one-step wet process of a ternary solution produces thin large-area films in which self-assembled, ordered nanopores of approximately 33 nm in diameter are developed even without an additional etching process. The study reveals that the small amount of amine-terminated poly(ethylene oxide) added to the binary blend of sulfonic-acid-terminated poly(styrene) and poly(2-vinylpyridine) efficiently activates the formation of spontaneous nanopores as a pore-generating agent. Our STENF significantly enhances the open-circuit voltage up to 1.5 times higher than that of a planar one, leading to an improved power density of approximately 77 μW/cm². The suitability for diverse conventional coating processes offers a convenient approach for fabricating high-performance STENFs not only on flat substrates such as metals, polymers, and oxides but also on topological ones including wrinkled, roughened surfaces, textile fibers, natural leaves, and fabrics over a large area.

Flexible, High-Power Density, Wearable Thermoelectric Nanogenerator and Self-Powered Temperature Sensor

We propose a flexible and wearable thermoelectric nanogenerator (FTEG) made from Bi₂Te₃, which allows high voltage and output power density. The proposed FTEG works as a thermopile with the end-to-end connection of 126 thermoelectric legs, and which is fabricated through magnetron sputtering Cu conductor on polyethylene terephthalate film. Bi, Te, Sb, and Se alloys are used to prepare thermoelectric materials by doping in a fixed proportion and zone melting, and nickel plating on the surface mitigates the deterioration of thermoelectric properties caused by the diffusion of Cu atoms or Cu⁺ ions. The thermoelectric figure of merit is stable and maintained above 0.7, up to 1.02. More flexibility is allowed by employing double sinusoidal serpentine connecting wires, and no significant property changes are observed even after being folded 200 times. When the temperature difference reaches 50 K, the output voltage of the FTEG will be no less than 520 mV, and the power density will reach 11.14 mW·cm^-2. By integration of a low-power, low-threshold voltage boost circuit on the back end of the FTEG, the electronic watch with a liquid crystal display screen can be easily powered to work properly. Furthermore, the FTEG is temperature-sensitive and, thus, can be used for temperature measurement with a resolution of 0.5 K. This work may have important prospects in flexible wearable physical sensors and individualized medical care.

Embedded Triboelectric Active Sensors for Real-Time Pneumatic Monitoring

Pneumatic monitoring sensors have great demands for power supply in cylinder systems. Here, we present an embedded sliding triboelectric nanogenerator (TENG) in air cylinder as active sensors for position and velocity monitoring. The embedded TENG is composed of a circular poly(tetrafluoroethylene) polymer and a triangular copper electrode. The working mechanism as triboelectric active sensors and electric output performance are systematically investigated. By integrating into the pneumatic system, the embedded triboelectric active sensors have been used for real-time air pressure/flow monitoring and energy storage. Air pressures are measured from 0.04 to 0.12 MPa at a step of 0.02 MPa with a sensitivity of 49.235 V/MPa, as well as airflow from 50 to 250 L/min at a step of 50 L/min with a sensitivity of 0.002 μA·min/L. This work has first demonstrated triboelectric active sensors for pneumatic monitoring and may promote the development of TENG in intelligent pneumatic system.

Rotating-Sleeve Triboelectric-Electromagnetic Hybrid Nanogenerator for High Efficiency of Harvesting Mechanical Energy

Currently, a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) have been hybridized to effectively scavenge mechanical energy. However, one critical issue of the hybrid device is the limited output power due to the mismatched output impedance between the two generators. In this work, impedance matching between the TENG and EMG is achieved facilely through commercial transformers, and we put forward a highly integrated hybrid device. The rotating-sleeve triboelectric-electromagnetic hybrid nanogenerator (RSHG) is designed by simulating the structure of a common EMG, which ensures a high efficiency in transferring ambient mechanical energy into electric power. The RSHG presents an excellent performance with a short-circuit current of 1 mA and open-circuit voltage of 48 V at a rotation speed of 250 rpm. Systematic measurements demonstrate that the hybrid nanogenerator can deliver the largest output power of 13 mW at a loading resistance of 8 kΩ. Moreover, it is demonstrated that a wind-driven RSHG can light dozens of light-emitting diodes and power an electric watch. The distinctive structure and high output performance promise the practical application of this rotating-sleeve structured hybrid nanogenerator for large-scale energy conversion.

Enhanced Triboelectric Nanogenerators Based on MoS2 Monolayer Nanocomposites Acting as Electron-Acceptor Layers

As one of their major goals, researchers attempting to harvest mechanical energy efficiently have continuously sought ways to integrate mature technologies with cutting-edge designs to enhance the performances of triboelectric nanogenerators (TENGs). In this research, we introduced monolayer molybdenum-disulfide (MoS₂) into the friction layer of a TENG as the triboelectric electron-acceptor layer in an attempt to dramatically enhance its output performance. As a proof of the concept, we fabricated a vertical contact-separation mode TENG containing monolayer MoS₂ as an electron-acceptor layer and found that the TENG exhibited a peak power density as large as 25.7 W/m², which is 120 times larger than that of the device without monolayer MoS₂. The mechanisms behind the performance enhancement, which are related to the highly efficient capture of triboelectric electrons in monolayer MoS₂, are discussed in detail. This study indicates that monolayer MoS₂ can be used as a functional material for efficient energy harvesting.

Achieving ultrahigh triboelectric charge density for efficient energy harvesting

With its light weight, low cost and high efficiency even at low operation frequency, the triboelectric nanogenerator is considered a potential solution for self-powered sensor networks and large-scale renewable blue energy. As an energy harvester, its output power density and efficiency are dictated by the triboelectric charge density. Here we report a method for increasing the triboelectric charge density by coupling surface polarization from triboelectrification and hysteretic dielectric polarization from ferroelectric material in vacuum (P ~ 10⁻⁶ torr). Without the constraint of air breakdown, a triboelectric charge density of 1003 µC m⁻², which is close to the limit of dielectric breakdown, is attained. Our findings establish an optimization methodology for triboelectric nanogenerators and enable their more promising usage in applications ranging from powering electronic devices to harvesting large-scale blue energy.

Triboelectric nanogenerators (TENGs) harvest ambient mechanical energy and convert it into electrical energy. Here, the authors couple surface polarization from contact electrification with dielectric polarization from a ferroelectric material in vacuum to dramatically enhance the TENG output power.

A smart mobile pouch as a biomechanical energy harvester towards self-powered smart wireless power transfer applications

A Smart Mobile Pouch Triboelectric Nanogenerator (SMP-TENG) is introduced as a promising eco-friendly approach for scavenging biomechanical energy for powering next generation intelligent devices and smart phones. This is a cost-effective and robust method for harvesting energy from human motion, by utilizing worn fabrics as a contact material. The SMP-TENG is capable of harvesting energy in two operational modes: lateral sliding and vertical contact and separation. Moreover, the SMP-TENG can also act as a self-powered emergency flashlight and self-powered pedometer during normal human motion. A wireless power transmission setup integrated with SMP-TENG is demonstrated. This upgrades the traditional energy harvesting device into a self-powered wireless power transfer SMP-TENG. The wirelessly transferred power can be used to charge a Li-ion battery and light LEDs. The SMP-TENG opens a wide range of opportunities in the field of self-powered devices and low maintenance energy harvesting systems for portable and wearable electronic gadgets.

Nanogenerators for Human Body Energy Harvesting

Humans generate remarkable quantities of energy while performing daily activities, but this energy usually dissipates into the environment. Here, we address recent progress in the development of nanogenerators (NGs): devices that are able to harvest such body-produced biomechanical and thermal energies by exploiting piezoelectric, triboelectric, and thermoelectric physical effects. In designing NGs, the end-user's comfort is a primary concern. Therefore, we focus on recently developed materials giving flexibility and stretchability to NGs. In addition, we summarize common fabrics for NG design. Finally, the mid-2020s market forecasts for these promising technologies highlight the potential for the commercialization of NGs because they may help contribute to the route of innovation for developing self-powered systems.