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Centuries ago trade in Chinese silk spawned the mighty transcontinental network of passages dubbed the Silk Route. Now, Indian scientists have found that the humble silk cocoon, the source of exquisite Tussar silks, may hold the key to the world's clean and green energy puzzle.
Experts at the Indian Institute of Technology-Kanpur (IIT-K) have fabricated simple devices from silk cocoon membranes (SCM) which, in the presence of water vapour, can generate enough electricity to run low-power electronic systems. In addition, they observed the electricity produced increases with the temperature.
For their experiments, the team at IIT-K's Department of Biological Sciences and Bioengineering (BSBE) and Center for Environmental Sciences and Engineering, used cocoons of Bombyx morii (silkworm of the mulberry tree) and antheraea mylitta (the non-mulberry species, the source of Tussar silk).
"The devices comprised pieces of SCM, cut into pieces of regular sizes, sandwiched between electrodes. The project's goal was to generate electricity cheaply and in a sustainable, eco-friendly way. The water vapour content (humidity) was never less than 80-90 percent.
"When the temperature was made to go up (around 80 degrees centigrade), the current also went up," Mainak Das, leader of the study and assistant professor, BSBE, told IANS over the phone from Kanpur.
For example, around three Bombyx cocoon pieces can light up one red LED of 1.6 volts.
"The LED is powered by extracting the electrical energy from cocoon. In the device, the cocoon has been treated as the circuit component. Interestingly, in the absence of humidity, the cocoon failed to produce electricity," Das explained.
Another crucial discovery of the project, by team member and corresponding author of the study Brindan Tulachan, who hails from Nepal, is that the innovative bio-hybrid device not only triggers energy production but also acts as some sort of a battery or capacitator.
"Think of rural areas where there is no electricity for hours on end. What if such batteries could supply power for a couple of hours?" Das asked.
These discoveries shed light on the thermo-electrical properties of silk, which is essentially natural protein fibre (mainly made up of fibroin), and opens up new avenues for harnessing natural products for green energy.
What this means is that silk or the protein, produced by thousands of other species of insects and silkworms, can be explored for such attributes and production of these bio-materials scaled up through different bio-technological interventions that are in use today, Das said.
"Just like Bombyx or Antheraea silk cocoons, other silk may have similar properties which need to be explored," he reckoned.
Moreover, it's not just the prospect of new green energy technologies. The process can be tapped to tackle waste heat management, especially the heat (humidified waste heat) given out by thermal and nuclear power plants.
"The main areas which contribute most in the heat dissipation are the power generation sector, thermal power plants, nuclear power plants, iron ore/steel industry, paper pulp industry and other industrial processes. These have a serious impact on the environment and the ecosystem.
"Building a system that could utilize the humidified waste heat for energy harvesting, thus reducing the environmental hazards, would be an ideal solution. If such structures (SCM devices) are emulated by exploiting modern micro and nano-fabrication tools, these could be an answer for mankind's ever-increasing demand for waste heat management and green and sustainable energy," Das added.
The researchers will now attempt to flesh out the exact mechanism at the atomic and sub-atomic levels (ionic or proton hopping) through which the electricity is generated.
So,the next time when you are out shopping for silk textiles, spare a thought for Mother Nature's power.
(Sahana Ghosh can be contacted at firstname.lastname@example.org)