A new, ultrathin energy harvesting system developed at Vanderbilt University has the potential to power your cell phone, fitness tracker and other personal electronic devices as you walk, wave and even when you are sitting down.
Based on battery technology and made from layers of black phosphorus that are only a few atoms thick, the new device generates small amounts of electricity when it is bent or pressed even at the extremely low frequencies characteristic of human motion.
Currently, there is a tremendous amount of research aimed at discovering effective ways to tap ambient energy sources. These include mechanical devices designed to extract energy from vibrations and deformations; thermal devices aimed at pulling energy from temperature variations; radiant energy devices that capture energy from light, radio waves and other forms of radiation; and, electrochemical devices that tap biochemical reactions.
Extracting usable energy from low frequency motion has proven to be extremely challenging. For example, a number of research groups are developing energy harvesters based on piezoelectric materials that convert mechanical strain into electricity. However, these materials often work best at frequencies of more than 100 Hertz. This means that they don’t work for more than a tiny fraction of any human movement so they achieve limited efficiencies of less than 5-10 percent even under optimal conditions.
The Vanderbilt lab’s ultrathin energy harvester is based on the group’s research on advanced battery systems. Over the past 3 years, the team has explored the fundamental response of battery materials to bending and stretching. They were the first to demonstrate experimentally that the operating voltage changes when battery materials are placed under stress. Under tension, the voltage rises and under compression, it drops.
One of the more futuristic applications of this technology might be electrified clothing. It could power clothes impregnated with liquid crystal displays that allow wearers to change colors and patterns with a swipe on their smartphone.
News Source: https://news.vanderbilt.edu/2017/07/21/device-harvests-electricity-human-motion/
