In an experiment reported in the scientific journal Advanced Materials in April, the NTU Singapore team showed that tapping on a 3cm by 4cm piece of a new polymer fabric generated enough electrical energy to light up 100 LEDs.
Washing, folding, and crumpling the fabric did not cause any performance degradation, and it could maintain stable electrical output for up to five months.
Materials scientist and NTU Associate Provost (Graduate Education) Professor Lee Pooi See, who led the study, said: “There have been many attempts to develop fabric or garments that can harvest energy from movement, but a big challenge has been to develop something that does not degrade in function after being washed, and at the same time retains excellent electrical output. In our study, we demonstrated that our prototype continues to function well after washing and crumpling. We think it could be woven into t-shirts or integrated into soles of shoes to collect energy from the body’s smallest movements, piping electricity to mobile devices.”
The prototype fabric generates electricity when it is pressed or squashed (piezoelectricity), and when it comes into contact or is in friction with other materials, like skin or rubber gloves (triboelectric effect).
NTU PhD student Jiang Feng, who is part of the research team, explained: “Embedding perovskites in PVDF-HPF increases the prototype’s electrical output. In our study, we opted for lead-free perovskites as a more environmentally friendly option. While perovskites are brittle by nature, integrating them into PVDF-HPF gives the perovskites exceptional mechanical durability and flexibility. The PVDF-HPF also acts an extra layer of protection to the perovskites, adding to its mechanical property and stability.”
The result is a prototype fabric that generates 2.34 watts per square meter of electricity.
To demonstrate how their prototype fabric could work, the NTU scientists showed how a hand tapping on a 3cm by 4cm piece of the fabric continuously could light up 100 LEDs, or charge several capacitors.
Prof Lee said: “Despite improved battery capacity and reduced power demand, power sources for wearable devices still require frequent battery replacements. Our results show that our energy harvesting prototype fabric can harness vibration energy from a human to potentially extend the lifetime of a battery or even to build self-powered systems. To our knowledge, this is the first hybrid perovskite-based energy device that is stable, stretchable, breathable, waterproof, and at the same time capable of delivering outstanding electrical output performance.”
The team is now looking at how the same fabric could be adapted to harvest different forms of energy.