Indian, S.Korean team recycles onion peels into nanogenerators

Kolkata, Nov 21 (IANS) Chopping onions makes you cry but now, thanks to scientists from India and South Korea, recycled onion skin waste offers reason to cheer for the green energy-powered smart devices sector.

Researchers at IIT Kharagpur and Pohang University of Science and Technology (Postech), South Korea, have fabricated biodegradable and biocompatible self-powered energy harvesters (nanogenerators) from onion skin waste for a range of biomedical applications.

Nanogenerators convert kinetic energy created from vibrational and mechanical sources into electrical power, doing away with the requirement of external circuits or batteries.

"The fabricated nanogenerator is capable of harvesting several types of mechanical energies, including body movements, wind flow and even machine vibrations," B.B. Khatua, Materials Science Centre, Indian Institute of Technology, Kharagpur, told IANS.

Technically such devices are called bio-piezoelectric nanogenerators (BPNG).

A single onion skin-based device can light up 30 green LEDs by repeated human finger touch response.

Energy harvesting through human body movement (joint movement) is an emerging trend in current science and technology for smart applications and is considered as a green alternative energy source, he said.

When six such onion skin nanogenerator units are used in series, a maximum output voltage of 106 Volt can be obtained, which instantaneously turns on "more than 70 combined LEDs" (red, green and blue), making the device highly suitable in rural areas, the researcher informed.

The electricity in the cellulose-based onion skin peels is produced as a result of structural changes in the cellulose under external mechanical stress/force including movements as delicate as a finger touch.

The innovation was a result of collaboration between Khatua's group (with his PhD student Sumanta Kumar Karan) at IIT Kharagpur and that of Jin Kon Kim's (with Sandip Maiti), Postech, South Korea and is published in Nano Energy journal in October.

"If we can design our devices in series under a treadmill, dance floor, and shoe-rubber, it can easily harvest green energy during walking or running," the scientists said in the study.

It is also very much sensitive to a leaf falling on it and efficient in monitoring signals arising out of small strains such as heart beat and throat movement during speaking, coughing and drinking.

Interestingly, the device is also capable of differentiating voice.

"The attachment of the nanogenerator to the throat can produce voltage signal during speech, the amplitude of which will depend on the intensity of throat vibration, making it suitable for voice/speech recognition," Khatua added.