- For the first time a piezoelectric nanogenerator that is capable of generating electrical energy from diverse sources — mechanical, acoustic and wind — has been developed.
- The device, fabricated by a team led by researchers from the Indian Institute of Technology (IIT) Kharagpur, has remarkable energy conversion efficiency of 62%, high output current (over 12 microampere), voltage (about 61.5 volt) and power density (over 9 mW per cubic cm).
- The high voltage of nanogenerator can be used to light up about 100 commercially available microwatt LEDs.
- The team used vitamin B2 to stabilise the beta phase of the piezoelectric polymer PVDF (polyvinylidene difluoride) and thereby enhance the piezoelectric performance.
- About 80% of PVDF is in alpha phase, which is not piezoelectric in nature.
- When vitamin B2 is added, it binds to PVDF and causes a change in alignment of the PVDF chain.
- This causes the PVDF to change its phase from alpha to predominantly (over 93%) beta, which is highly piezoelectric.
- The nanogenerator is also completely organic and biocompatible and so can be used for both in vitro and in vivo applications
- The proportion of beta phase in PVDF and hence the output voltage and current increased with increasing amount of vitamin B2 added to it reaching a peak at 5 weight percentage.
- To fabricate the nanogenerator, the researchers made two thin films made by mixing vitamin B2 and PVDF and spin coating the solution.
- The films with electrodes attached and separated by nylon net are then taped together. The device was found to have good flexibility and durability.
What about the High sensitivity?
- The device was found to be highly sensitive to even very small external force such as touching, bending and air-flow.
- It also showed high mechanical durability — no change in output performance was seen for about 1,80,000 cycles — and chemical stability for up to 10 weeks, making it suitable for various applications including e-health care monitoring.
- When made into a thin film and placed on the wrist, the device was able to convert the biomechanical energy to electrical energy (0.15 volt).
- Same when it was placed on the throat and the person was speaking (0.5 volt), gargling (1.6 volt) or swallowing (0.29 volt).
- When placed on speakers, the device was able to harvest sound energy.
- Similarly, when placed on the lid of a table fan it could convert wind pressure into electricity.
- We want to use this device to convert heartbeat to power a pace maker by using a rechargeable battery.
- We are also trying to explore large-scale application by placing the device on dancing floor, entrances to high throughput passages and storing the electrical energy in capacitors to run small devices.
