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Nano-films will use human energy to power devices

Dr Madhu Bhaskaran and colleagues from RMIT University and the Australian National University have measured the potential of piezoelectric nano-films to provide energy for small electronic devices.

Their findings are reported in today's Advanced Functional Materials.

"With the drive for alternative energy solutions, we need to find more efficient ways to power microchips, which are the building blocks of everyday technology like the smarter phone or faster computer," says Bhaskaran.

"Piezoelectrics could be integrated into running shoes to charge mobile phones, enable laptops to be powered through typing or even used to convert blood pressure into a power source for pacemakers — essentially creating an everlasting battery."

Research into the possibility of piezoelectric material using human energy to power devices is not a new field.

Previous research has focused on using nanorods and nanowires to generate energy, but Bhaskaran and her colleagues are one of the first to study the potential of nano-films.

"It is not as exotic as what other people have done with nanowires and nanorods," says Bhaskaran. However the application of this piezoelectric thin film "makes it much easier to integrate it into existing technology".

Should be a simple process

Electronic devices already have integrated chips which are coated in thin films, so the integration of piezoelectric films onto the chip would be a simple process, she says.

To assess voltage generation they coated a silicon substrate with 700 and 1400 nanometre thick lead-based (PSZT) films and applied very small forces of between 0.1 millinewtons (mN) and 2.5 mN.

Then they created 200 to 400 nm "nano-islands" from the 700 nm film to assess whether textured surfaces created more energy than continuous surfaces.

While the planar geometry had no influence on the voltage generation, it did increase the current.

Baskharan and her team achieved voltage outputs of up to 40 mV and currents up to around 200 picoamps (pA). They found the effective power generated by nano-films was around 250 microwatts with a force of 5 mN.

That's about 10 times less than the power you need to run a smart phone, so the next challenge will be to amplify the electrical energy so it can be integrated into electrical devices, says Bhaskaran.

"That will be fairly straightforward to do," she says.

"All the semiconductor fabrication or any fabrication facility already has the capabilities to do thin films and patterning."

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