Highly stretchable hydroxyapatite bionanocomposite for high-performance triboelectric nanogenerators.

Renewable energy has been a focus in recent years. Triboelectric nanogenerators (TENGs) have potential for converting mechanical energy into electricity. However, there are restrictions on the use of biological materials and bionanocomposites, such as the high cost and complexity of the synthesis process, poor stability, and inadequate output performance. To overcome the constraints of TENGs, we have turned to hydroxyapatite, a biological substance with great biocompatibility and high mechanical strength that can be manufactured from waste materials. We successfully developed a negative triboelectric bionanocomposite hydroxyapatite (HA) loaded polydimethylsiloxane (PDMS) to harness energy from biomechanical sources such as wearable devices. A TENG (2 × 2 cm2) with a pushing force of 2 N and different amounts of HA in PDMS can produce highly stable output voltage, current, surface charge density, and power density values of 300 V, 22.4 µA, 90.36 µC m-2, and 27.34 W m-2, which are 6, 9, and 10 times higher than those without HA, respectively. These improvements were attributed to the highest observed surface potential of 1512 mV. After 20 000 cycles of contact-separation, the HA/PDMS-TENG shows exceptionally stable performance. Furthermore, adding HA improves the mechanical properties and the stretchability of the bionanocomposite. The HA/PDMS bionanocomposite exhibits remarkable stretchability of more than 290%. Effectively harvesting energy from body movements, the TENG gadget may be used to charge multiple commercial capacitors, drive up to 100 LEDs, and power a low-power electronic device. Self-powered sensing and wearable devices are made possible by the HA/PDMS-TENG, which allows their large-scale preparation and deployment.

Magnetic Force Enhanced Sustainability and Power of Cam-Based Triboelectric Nanogenerator.

Since the first invention of triboelectric nanogenerators (TENGs) in 2012, many mechanical systems have been applied to operate TENGs, but mechanical contact losses such as friction and noise are still big obstacles for improving their output performance and sustainability. Here, we report on a magnet-assembled cam-based TENG (MC-TENG), which has enhanced output power and sustainability by utilizing the non-contact repulsive force between the magnets. We investigate the theoretical and experimental dynamic behaviors of MC-TENGs according to the effects of the contact modes, contact and separation times, and contact forces (i.e., pushing and repulsive forces). We suggest an optimized arrangement of magnets for the highest output performance, in which the charging time of the capacitor was 2.59 times faster than in a mechanical cam-based TENG (C-TENG). Finally, we design and demonstrate a MC-TENG-based windmill system to effectively harvest low-speed wind energy, ~4 m/s, which produces very low torque. Thus, it is expected that our frictionless MC-TENG system will provide a sustainable solution for effectively harvesting a broadband of wasted mechanical energies.

Continuous scavenging of broadband vibrations via omnipotent tandem triboelectric nanogenerators with cascade impact structure.

Ambient vibration energy is highly irregular in force and frequency. Triboelectric nanogenerators (TENG) can convert ambient mechanical energy into useable electricity. In order to effectively convert irregular ambient vibrations into electricity, the TENG should be capable of reliably continuous operation despite variability in input forces and frequencies. In this study, we propose a tandem triboelectric nanogenerator with cascade impact structure (CIT-TENG) for continuously scavenging input vibrations with broadband frequencies. Based on resonance theory, four TENGs were explicitly designed to operate in tandem and cover a targeted frequency range of 0-40 Hz. However, due to the cascade impact structure of CIT-TENG, each TENG could produce output even under non-resonant conditions. We systematically studied the cascade impact dynamics of the CIT-TENG using finite element simulations and experiments to show how it enables continuous scavenging from 0-40 Hz even under low input accelerations of 0.2 G-0.5 G m/s2. Finally, we demonstrated that the CIT-TENG could not only scavenge broadband vibrations from a single source such as a car dashboard, but it could also scavenge very low frequency vibrations from water waves and very high frequency vibrations from air compressor machines. Thus, we showed that the CIT-TENG can be used in multiple applications without any need for redesign validating its use as an omnipotent vibration energy scavenger.

Effects of Embedded TiO2-x Nanoparticles on Triboelectric Nanogenerator Performance.

Triboelectric nanogenerators (TENGs) are used as self-power sources for various types of devices by converting external waves, wind, or other mechanical energies into electric power. However, obtaining a high-output performance is still of major concern for many applications. In this study, to enhance the output performance of polydimethylsiloxane (PDMS)-based TENGs, highly dielectric TiO2-x nanoparticles (NPs) were embedded as a function of weight ratio. TiO2-x NPs embedded in PDMS at 5% showed the highest output voltage and current. The improved output performance at 5% is strongly related to the change of oxygen vacancies on the PDMS surface, as well as the increased dielectric constant. Specifically, oxygen vacancies in the oxide nanoparticles are electrically positive charges, which is an important factor that can contribute to the exchange and trapping of electrons when driving a TENG. However, in TiO2-x NPs containing over 5%, the output performance was significantly degraded because of the increased leakage characteristics of the PDMS layer due to TiO2-x NPs aggregation, which formed an electron path.