Good vibrations

A UK company has developed a wireless MEMs device that harvests kinetic energy from natural movement in the environment and converts it into usable electrical energy.

In an age of ever more pervasive electronics, the inflexibility of traditional power sources and the short life of batteries is becoming more and more of a headache for designers.

Help could be at hand, however, in the form of a wireless MEMS device that harvests kinetic energy from natural vibrations in the environment and converts it into usable electrical energy to power a range of sensors, microprocessors and transmitters.

Southampton-based Innos has created a system that uses a simple cantilever device, fixed at one end with a weight at the other. A range of external environmental factors will cause the beam of this cantilever to vibrate. As it does so, a series of magnets attached to the beam move past a coil and generate a few hundred microwatts of power, a sufficient enough charge, according to Innos, to power sensors, microprocessors or transmitters.

The development builds on work carried out by another Southampton company, Perpetuum, which has built a matchbox-sized system that is capable of generating energy. Innos has been working on reducing the size of the device by embedding the technology in silicon, and has produced a silicon MEMS microgenerator capable of driving small sensors and RF transmitters, allowing for a self-powered system.

Sales and marketing manager Dr Alec Reader said that the company is currently looking at embedding the silicon technology into pacemakers to aid the longevity before the battery needs replacing. ‘Currently, pacemakers last a couple of years before a new battery needs to be fitted,’ said Reader. ‘It is stupid — you want something you can put in and leave there.’

He claimed that Innos’ device will complement the existing battery to prolong its lifespan, reducing the need to replace it. He added, however, that the long-term aim of patients powering their own pacemakers by simply moving about is still a little way off. The project is still in its early phases. A team of doctors and heart surgeons is working with a pacemaker manufacturer, but the next hurdle is acquiring sufficient funding to pursue it further — something Reader is confident will happen. Innos is currently trying to drum up EU and government funding.

Aside from pacemakers, the technology has numerous other possible applications. Monitoring machinery within industry such as motors, turbines and pumps has been discussed, and other suggestions include powering and delivering sensor signals for testing rotating parts, wheels and rotors. This could also be expanded to remote sensors on permanent and inaccessible structures such as bridges and roads.

Reader explained that most of the work being done is at micron level, and uses silicon-embedded technology which has advantages over other materials. ‘Silicon is a very controlled technology, can cope with very, very high tolerances, and can be made to a very high precision.’ This is important as the device has to be tuned to the correct frequency of the surrounding vibrations so the resonance is at optimum to produce the maximum possible energy output.

Reader said that while it is appealing to produce the device using other materials like plastics, it’s not currently possible to manufacture them to the required precision. ‘Materials have got to be able to lend the right mechanical and physical properties to establish the resonance,’ he said. ‘The technology is all very new and we have only just started to explore all the options.’ said Reader. It will be interesting to see how far it can go and how long it will take. 

Australia moves towards kinetic power

The work by Innos and Perpetuum represents a significant step to producing high-precision, small-scale kinetic wireless devices, but the concept of harvesting low-level vibrations to produce energy is not entirely new. Perhaps the best-known existing example is the Seiko kinetic watch. This uses an oscillating weight that is rotated by the movement of the wearer’s wrist, that transforms the movement into a magnetic charge, then into electricity that is then stored in a capacitor or rechargeable battery.

Other companies have also looked into technology though not at the micron scale realised by Innos. Australia’s Centre for Energy and Greenhouse Technologies (CEGT) is investing in the development of a kinetic energy cell that can convert energy from any kind of movement into storable power for batteries and could complement or replace small conventional batteries in a range of everyday applications. While the latest design is the size of a 9V battery, there are plans to make it even smaller and develop the cell for wider market applications.

The technology, developed by Melbourne’s government-funded co-operative research centre for micro-technology, consists of just seven components and features innovative coil construction. In a similar approach to the Innos device, the technology can be tuned to optimise operations in a wide range of vibration environments and potential applications.

According to the CEGT, the kinetic cell could be used in applications such as vehicle tolling and shipping container electronic identification devices, thereby negating the need to replace batteries. This means the device could operate indefinitely without needing to be opened up. The cell unit can also be sealed which makes it suitable for harsh operating conditions. It has recently been announced that the CEGT will invest A$125,000 (around £51,000) to commercialise the new cell, with a possible A$1m to be considered in the future.