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It is a battery if it moves

Devices, sensors and lights everywhere. These elements increasingly surround us in a modern setting. What do all these cogs of technology need in common? Power, to run uninterrupted. Often this power is provided by bulky batteries that need timely replacement making them an inconvenience. What if these devices, sensors and tiny lights could run on energy extracted out of thin air!

Researchers at the Indian Institute of Science, Bangalore have now devised a technology which can efficiently extract energy from vibrations that are almost always present around us. Though not from thin air, this development has a wide scope of applications and could power smalls LED lights, fire and smoke alarms, biomedical devices to name a few.

Ever felt the vibrations from a heavy vehicle passing nearby? How about those from a powerful water pump, an AC, a fridge? These are called ambient vibrations and surround us endlessly. The idea to extract energy from them has been around for some time. There are, for example, watches that can charge themselves from the user's movements. To harvest this energy we need something called a piezoelectric material, which generates a voltage whenever it is squeezed, bent or twisted. However, often this voltage is too small to be directly useful.

Writing in IEEE Sensors Journal, the lead author Rammohan and team have created a novel design for harvesting energy using a piezoelectric material called Polyvinylidinefluoride (PVDF). Their design consists of stacking many PVDF layers on top of each other in a manner that it looks like a step farm. This design effectively generates more strain and thus more power. Their design is 90% more efficient than previous designs and with this increased efficiency they can power many devices and sensors that would not have been possible before. The authors also provide a scheme by which one can examine harvesters of any shape and size.

The work is so exciting that it is already finding many use cases. Prof. Rudra Pratap, from the Centre for Nano Science and Engineering who led the project said "We are currently working on lighting up a lot of LEDs with vibration energy harvested from exhaust ducts located on the terrace of our Centre. We are also working on temperature and gas sensors, and fire alarms that can be run with vibration energy and installed in buses, trains, etc." They are also in talks with the National Aerospace Laboratories, Bangalore to further improve the design of these energy harvesters and use them in sensing applications which require low power.

"Structural health monitoring, surveillance and biomedical sensing are some of the potential societal applications that can be self powered using the kind of energy harvesters we are pursuing." says Rammohan. These developments in energy harvesters also fall very well in place with the electronics industry, where devices are getting smaller and more energy efficient with time. We hope that soon this work will lessen the nuisance that batteries and charging are.

About:

Rudra Pratap is a Professor and the Chairperson at the Centre for Nano Science & Engineering, Indian Institute of Science, Bangalore.

Contact: 080- 2293 3250, pratap@cense.iisc.ernet.in.

The paper has appeared in the IEEE Sensors Journal.