A pacemaker runs only as long as its battery, after which the battery needs to be replaced. New research has come up with an alternative that can power the pacemaker continuously — a nanogenerator that harvests electricity out of spider silk. Scientists at IIT Kharagpur, along with a team of researchers from South Korea, have devised a self-powered, piezoelectric nanogenerator that can harvest green energy from various mechanical and biomechanical motions.
Piezoelectricity is the generation of electric charges in certain solid materials in response to applied mechanical stress — such as the body’s motion, wind and water flow, or sound vibration. A piezoelectric nanogenerator can harvest external kinetic or mechanical/bio-mechanical energy into electrical energy via action by means of a nano-structured piezoelectric material.
The research, published in Nano Energy, describes how piezoelectricity can be generated by applying pressure on fibre — in this case spider-silk fibre. IIT Kharagpur scientists say this technology can be used in healthcare monitoring, such as in pacemakers and other medical equipment.
“There are many materials in nature which have piezoelectric properties. When pressure is applied, it leads to changes in the molecular structure of the material, making it capable of harvesting mechanical/biomechanical energy into green electricity. When capacitors are attached to the external circuit, the electrical energy can be stored and this becomes an alternative energy source to thermal energy or hydroelectric energy or solar energy,” said Professor B B Khatua of IIT Kharagpur’s Material Science Centre, who led the research. “There are various ceramic or metal-oxide-based piezoelectric materials. But due to their brittleness and toxic nature, these materials have limitations for application inside the human body. Spider silk, however, is both biocompatible and biodegradable and is therefore perfect for being used inside the body.”
While the pacemaker will keep the heart ticking, the heartbeat will in turn keep the pacemaker going. “In battery-operated pacemakers, once the life of the battery is over, you need to replace it. Assembling a spider-silk-based nanogenerator as a self-chargeable power source, the energy required to make the pacemaker work can be created by the heartbeat. Every time the heart beats, it will create external pressure on the spider silk, making it generate energy,” Prof Khatua said.
The nanogenerator was prepared by spraying water on spider silk and wrapping it around the device. The power generated from a single unit lights up 25 green LEDs instantly. Prof Khatua said it can be used not only in pacemakers but in many other devices, and also for harvesting green energy and even for large-scale industrial applications.
“The self-powered, spider-silk-based flexible nanogenerator is extremely sensitive to even minute pressure generated from body motions, even the very small pressure arising from arterial pulse (signals arising out of small strains), throat movement during coughing, speaking, and drinking. This shows its potentiality in healthcare-monitoring applications… Its sensitiveness could also be used to monitor robotic applications,” he said.
It is the first time that a natural product like spider silk has been effectively used as a piezoelectric nanogenerator without any chemical treatment. Prof Khatua said the same team had conducted similar research with onion peels, which was published last year by IIT Kharagpur. The spider-silk energy technology took one year to devise.
Professor Khatua said devices made of these materials have the added advantage of size. “They can be thin, like a band-aid,” he said. “It can externally be used for small electronic devices such as mobile phones, watches and calculators among others.” Prof Khatua’s team included IIT research student Sumanta Kumar Karan, in collaboration with Prof Jin Kon Kim and Dr Sandip Maiti (ex-PhD student of Prof Khatua) from POSTECH, South Korea. The piezoelectric nature of the spider silk was further tested and improvised by a research team of Prof Yunseok Kim from SKKU, South Korea. IIT Kharagpur will apply for a patent and then look at commercial technology transfer.