Mobile devices powered just by tapping your finger

We produce small amounts of energy in everything we do, movements like walking and tapping on a keyboard release energy that is then mostly dissipated. However, new research by a team from India and Germany has shown a way to develop flexible and biodegradable devices that generate power from such common movement that could lead to a new generation of electronic devices that never need to be charged.

Although there has been many studies into nanogenerators that are able to capture such energy and convert it into electricity to power mobile devices, this investigation – as reported in ACS Applied Materials & Interfaces [Tamang et al. ACS Appl. Mater. Interfaces (2015) DOI: 10.1021/acsami.5b04161] – looked to improve nanogenerators in terms of their recharging and biodegradability. The device they developed uses a flexible, biocompatible polymer film made from polyvinylidene fluoride (PVDF), before DNA is added to improve the material's ability to harvest energy from everyday motion and then turn it into electrical power.

This breakthrough could resolve those perennial problems around portable electronics of their short battery life and need for power sources dependent on fossil fuels while offering biocompatibility, flexibility and low cost. The device, which was shown to light up 22 to 55 green or blue light-emitting diodes powered only by gentle tapping, is capable of harvesting energy from mechanical stresses including human touch, walking, machine vibration and football juggling.

"[The device] exploited the electrical properties of the DNA molecules to generate useful piezoelectric power that can be implemented to run portable devices.”Dipankar Mandal

The nanogenerator exhibited high piezoelectric energy conversion efficiency that facilitated the immediate switching on of the diodes. Using a flexible piezoelectric film meant the nanogenerator could avoid the usual stretching, poling and inclusions of inorganic nanoparticles to induce the electroactive phase, especially as stretching has a negative effect on the performance and lifetime of such devices, while electrical poling consumes power and reduces production yield. The DNA–PVDF piezoelectric composite polymer is eco-friendly and has great flexibility, and can be moulded into different configurations with less volume and weight.

As lead researcher Dipankar Mandal points out, they “exploited the electrical properties of the DNA molecules to generate useful piezoelectric power that can be implemented to run portable devices.” The team now hope to modify the device to function as a self-powering system in implantable biomedical devices, where the nanogenerator could generate electricity from the blood flow of the patient, and could also find uses in structural monitoring, and even in determining the quality of fruit and in tea grading.