Concerns surrounding the sustainability of our environment continue to receive close attention around the world. Global citizens look for new technology to provide them with improved creature comforts while, at the same time, technology that decreases its footprint on the environment. This increasing demand for a cleaner and more sustainable power source pushes researchers to determine how to best convert environmental energy into electricity.

A further positive outcome of this desired technology is the step it takes in getting us closer to improved and sustainable wearable electronics. Pubic demand for Internet of things, (the connection through the Internet of computing devices embedded in everyday objects, allowing them to send and receive data) grows daily as we become an ever more mobile society wanting to retain contact with the Internet at all times.

Wearable electronics require lightweight power supplies combined with a high-energy storage performance. Examining this issue revolves around the use of electromagnet generators (EMGs), piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs).

An EMG is a device that transforms mechanical energy into electrical energy through the process of electromagnetic induction and is useful for large-scale power generation. A PENG is a device for harvesting energy, and is able to convert external kinetic energy into electrical energy using nano-structured piezoelectric material. Furthermore, it is useful in self-powered, miniaturized devices.

Current technology revolves around the triboelectric nanogenerator (TENG), which converts mechanical energy into electricity. TENGs are limited in terms of their usefulness in the field of wearable electronic technology, as they require a rectifier and electromagnetic shielding which limits their portability and usability in miniaturized devices. TENGs also experience electrostatic breakdown, which occurs when electronic components fail as a result of static electricity.

Resolving these limitations is the focus of Liu et al. (https://advances.sciencemag.org/ content/5/4/eaav6437.full) resulting in the invention of DC-TENG, an advanced version of TENG. DC-TENG relies on the triboelectric effect, which is a type of contact electrification in which particular materials become electrically charged after coming into contact with a different material and then separated. Specifically, the researchers created artificial lightning utilizing a charge-collecting electrode (CCE), frictional electrode (FE) and triboelectric layer. The CCE and FE both consisted of copper electrodes while the triboelectric layer consisted of a polytetrafluoroethylene (PTFE) film attached to an acrylic sheet.

A high electrostatic field built between the CCE and PTFE film ionized the surrounding air, creating a flow of electrons from the PTFE to the CCE. This flow of electrons is essentially artificial lightning. The CCE collected the charges created by the energy of air breakdown.

Researchers produced continuous DC output by moving the slider periodically. As a result, self-powered DC-TENGs have the ability to run electronics directly through the conversion of mechanical energy.

The invention of the DC-TENG creates a method to convert mechanical energy to electricity for powering electronics in a way easily utilized within the miniaturization of wearable electronics.

For additional information, refer to:

Mark K. Debe. Electrocatalyst approaches and challenges for automotive fuel cells, Nature (2012). DOI: 10.1038/nature11115

Jie Wang et al. Achieving ultrahigh triboelectric charge density for efficient energy harvesting, Nature Communications (2017). DOI: 10.1038/s41467-017-00131-4

Zhen Wen et al. Self-powered textile for wearable electronics by hybridizing fiber-shaped nanogenerators, solar cells, and supercapacitors, Science Advances (2016). DOI: 10.1126/sciadv.1600097