Researchers at Cambridge University have developed a device that converts the ambient vibrations in buildings and infrastrucure like tunnels and bridges into electricity sufficient to power small remote monitoring devices.
The micro-electromechanical system (MEMS) “amplifier” paves the way for more effective monitoring of the structral health of buildings and infrastructure and the better prevention of major incidents, such as the recent tunnel collapse near Tokyo, which tragically killed nine people.
Professor Kenichi Soga,a member of the research team that developed the prototype device, said: “Wireless sensors are one way to better look after infrastructure, and it’s something that industry is interested in doing, but batteries are always the sticking point. It’s not the cost of the batteries that is the issue – it’s the cost of human power to replace the batteries.”
Self-powered battery-less devices are not new and energy “harvesting” is currently used to power consumer devices such as digital wristwatches and handheld torches. However, these technology has a low output power density. In additon, the vibrations experienced by bridges, tunnels and roads are also “wideband”, whereas conventional energy harvesters have a narrow operational frequency.
The research team has overcome these issues by basing their harvester on a phenomenon known as parametric resonance. The energy harvesting device consists of a micro-cantilever structure and a transducer. When force is applied to the cantilever perpendicular to the length instead of transversely, parametric resonance can be achieved, generating more energy from the same amount of vibration.
As a MEMS device, it is also hoped the it can be batch manufactured using principles common to the seminconductor industry, potentially enabling low-cost battery replacement, large-scale volume production and co-integration with sensors and interface electronics to realise truly autonomous smart sensors.
Preliminary results of the prototype were presented at the PowerMEMS conference in Atlanta in December and the device is currently being commercialised by Cambridge Enterprise, the University’s technology transfer office.
Outside of the construction industry, the researchers hope the device could also be used to power wearable medical devices or to extend the life of batteries in mobile phones.