This article describes a simple, cost-effective, and scalable approach to fabricate a triboelectric nanogenerator (NG) with ultrahigh electric output. Triggered by commonly available ambient mechanical energy such as human footfalls, a NG with size smaller than a human palm can generate maximum short-circuit current of 2 mA, delivering instantaneous power output of 1.2 W to external load. The power output corresponds to an area power density of 313 W/m(2) and a volume power density of 54,268 W/m(3) at an open-circuit voltage of ~1200 V. An energy conversion efficiency of 14.9% has been achieved. The power was capable of instantaneously lighting up as many as 600 multicolor commercial LED bulbs. The record high power output for the NG is attributed to optimized structure, proper materials selection and nanoscale surface modification. This work demonstrated the practicability of using NG to harvest large-scale mechanical energy, such as footsteps, rolling wheels, wind power, and ocean waves.

A harmonic-resonator-based triboelectric nanogenerator (TENG) is presented as a sustainable power source and an active vibration sensor. It can effectively respond to vibration frequencies ranging from 2 to 200 Hz with a considerably wide working bandwidth of 13.4 Hz. This work not only presents a new principle in the field of vibration energy harvesting but also greatly expands the applicability of TENGs.

We report human skin based triboelectric nanogenerators (TENG) that can either harvest biomechanical energy or be utilized as a self-powered tactile sensor system for touch pad technology. We constructed a TENG utilizing the contact/separation between an area of human skin and a polydimethylsiloxane (PDMS) film with a surface of micropyramid structures, which was attached to an ITO electrode that was grounded across a loading resistor. The fabricated TENG delivers an open-circuit voltage up to −1000 V, a short-circuit current density of 8 mA/m2, and a power density of 500 mW/m2 on a load of 100 MΩ, which can be used to directly drive tens of green light-emitting diodes. The working mechanism of the TENG is based on the charge transfer between the ITO electrode and ground via modulating the separation distance between the tribo-charged skin patch and PDMS film. Furthermore, the TENG has been used in designing an independently addressed matrix for tracking the location and pressure of human touch. The fabricated matrix has demonstrated its self-powered and high-resolution tactile sensing capabilities by recording the output voltage signals as a mapping figure, where the detection sensitivity of the pressure is about 0.29 ± 0.02 V/kPa and each pixel can have a size of 3 mm × 3 mm. The TENGs may have potential applications in human–machine interfacing, micro/nano-electromechanical systems, and touch pad technology.

Harvesting thermoelectric energy mainly relies on the Seebeck effect that utilizes a temperature difference between two ends of the device for driving the diffusion of charge carriers. However, in an environment that the temperature is spatially uniform without a gradient, the pyroelectric effect has to be the choice, which is based on the spontaneous polarization in certain anisotropic solids due to a time-dependent temperature variation. Using this effect, we experimentally demonstrate the first application of pyroelectric ZnO nanowire arrays for converting heat energy into electricity. The coupling of the pyroelectric and semiconducting properties in ZnO creates a polarization electric field and charge separation along the ZnO nanowire as a result of the time-dependent change in temperature. The fabricated nanogenerator has a good stability, and the characteristic coefficient of heat flow conversion into electricity is estimated to be ∼0.05−0.08 Vm 2 /W. Our study has the potential of using pyroelectric nanowires to convert wasted energy into electricity for powering nanodevices. KEYWORDS: ZnO nanowires, pyroelectric effect, nanogenerators, Schottky contact, Seebeck effect W asted heat is a rich source of energy that could be harvested. In 2010, for example, more than 50% of the energy generated from all sources in the U.S. was lost mainly in the form of wasted heat, 1 which presents us with a great opportunity to harvest this type of energy using nanotechnology. Harvesting thermoelectric energy mainly relies on the Seebeck effect that utilizes a temperature difference between the two ends of the device for driving the diffusion of charge carriers. 2,3 The presence of a temperature gradient is a must for the conventional thermoelectric cell. However, in an environment that the temperature is spatially uniform without a gradient, such as in outdoor in our daily life, the Seebeck effect is hardly useful for harvesting thermal energy arising from a time-dependent temperature fluctuation. In this case, the pyroelectric effect is the choice, which is about the spontaneous polarization in certain anisotropic solids as a result of temperature fluctuation, 4 but there are few studies about using pyroelectric effect for harvesting thermal energy. 5 Recently, piezoelectric ZnO nanowires have been effectively used to harvest small-scale mechanical energy. 6−9 The core of the piezoelectric nanogenerator (NG) is to utilize the piezoelectric potential (piezopotential) in the nanowires created by mechanical straining to drive the flow of electrons in the external load. Piezopotential can be generated by either strain or by temperature due to the anisotropic physical properties of ZnO. Here, we demonstrate the first application of converting heat energy into electricity by means of pyroelectric ZnO nanowire arrays. By using the coupling of the pyroelectric and semiconducting properties in ZnO, a polarization electric field and charge separation can be created along the ZnO nanowire as a result of the time-dependent...

No abstract