Energy Management Group
Department of Electrical & Electronic Engineering
Merchant Venturers Building
Woodland Road
Bristol BS8 1UB
United Kingdom
T +44 117 954 5499
F +44 117 954 5206
E energy-management
@bristol.ac.uk
Recent developments in functional materials, micro-engineering and nanoscience have provided us for the first time with the possibility of creating completely autonomous miniature medical and security sensors. We will no longer need bulky batteries to power them, instead, miniature embedded power sources are being developed which will derive their energy from their surroundings.
In 1988, researchers of the University of Michigan succeeded in developing a blood pressure sensing element which was so small that it was hard to see with the naked eye. Incredibly, this speck, measuring 0.35mm × 0.1mm × 1mm, included a micro-machined sensing structure and the electronics required to take the measurement. Recently, nanoscience and Micro-Engineering have successfully created a wonderful selection of miniature sensing elements, from nanoparticle-based electronic “noses” which can detect a fire before it breaks out into flames, to micro-machined mass spectrometers, which can analyse air and look for the faintest signs of dangerous gasses.
In order to take advantage of the miniaturisation of sensing elements, the energy supply needs to be scaled appropriately, in order to obtain small and independent sensors.
This, however, reduces the energy available and therefore requires a sensor to have a clever energy management system that can accumulate energy over time. Also, the communication of data needs to occur wirelessly - requiring more power than communication over wire. Data must be sent in efficient short bursts. An example of this kind of routine can be found in a radio developed by the Energy Management Group. The radio has a core that goes to sleep hundreds of times a second, only waking up for a few millionths of a second at a time in order to save energy. This principle is now being applied to medical sensors, and to sensors that monitor the flow of energy in homes.
Miniature generators are being developed which could power an efficient sensor independently. These generators extract energy from waste heat flow or from vibration of their surroundings and condition the energy to a form which can be used by the sensor. The group aims to demonstrate autonomous healthcare, energy and security sensors over the coming years.