Editorial Feature

Self-Powered Sensors

The evolution of self-powered sensors was spurred on by the inconvenience of having to replace batteries in devices such as implanted biomedical monitoring or treatment systems, and devices for monitoring machinery, infrastructure or industrial systems whose batteries are mostly fitted in difficult-to-access areas or spread over a wide area.

MIT researchers among others have found a solution. The new technology that they have come up with will curb the need for replacement of batteries; instead devices will be powered by differences in temperature between the body and the surrounding air.

Based on a concept already in existence, a research team from MIT was involved in developing new energy-scavenging systems.

The concept of harvesting energy from differences in temperature has been used by NASA where their space probes harvested heat from radioactive plutonium. Similarly, certain semiconductor materials tend to produce a flow of electrical current when one side is hotter than the other. These materials are used in coolers and heaters in the food and beverages sector. MIT researchers hope to reach the theoretical limits of efficiency in utilizing this heat energy.

EnOcean GmbH is a German patented self-powered wireless technology company that produces devices to collect cost-free energy existing in the environment such as pressure, linear motion, differences in temperature, and light, and convert that into energy to be used electrically. They have been combining miniaturized energy harvesters and highly efficient wireless technology to create service-free wireless sensor solutions for use in buildings and industrial automation.

Research

The 2011 Fukushima Daiichi nuclear disaster in Japan prompted U.S. researchers to develop self-powered sensors that could monitor a nuclear reactor in a disaster and even when electrical power to the reactor falters.

A report from the American Institute of Physics in 2012 stated that Penn State researchers along with the Idaho National Laboratory had created a self-powered sensor that could harness heat from a nuclear reactor’s extreme operating environments to transmit data without the need for electronic networks.

The self-powered sensor was designed with a technology called thermoacoustics to produce energy from the heat with a nuclear reactor. Thermoacoustics is based on the interaction between heat and sound waves.

Yeatman E.M. et al from the Imperial College London presented a paper with a proposal for a hybrid powering system of energy harvesting and wireless power delivery for data transmission.

The researchers were keen on eliminating the major limitation in the development of biosensors for in-body applications, which is the need for electrical power.

The use of motion-powered energy harvesting devices for in-body use would be much more feasible as the electrical power it required would not exceed a few microwatts for devices of standard size.

In 2010, Wang Z.L. from the School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, USA presented his theory in a paper titled ‘Toward self-powered sensor networks’.

He sees the future of nanotechnology developing in the direction of combining separate nanodevices into a single nanosystem capable of acting like living species with abilities such as communication, sensing, controlling and responding.

The key to the success of this nanosystem lies in providing adequate power via a nano-power source so as to ensure that the system remains very small at the same time highly efficient. To achieve this, Dr. Wang advocates the self-powering approach, which would be a new model for achieving sustainable self-sufficient nanosystems that would have numerous applications in myriad fields.

Future Developments

Dong Ha and his team of embedded systems researchers are working with mechanical engineers headed by Dan Inman from the Center for Intelligent Material Systems and Structures (CIMSS) to develop energy harvesting technology for embedded devices.

Their goal is to finally arrive at self-powered sensors specifically for hard-to-reach spots like bridges and helicopter turbine engines.

Infinite Power Solutions, Inc. (IPS), a solid-state, rechargeable, thin-film battery solutions provider, released the IPS-EVAL-EH-02 Wireless Environmental Sensor Energy Harvesting Evaluation Kit in 2012. They hope that this evaluation kit will help designers develop self-powered wireless sensors for smart home and building automation systems.

In 2012, Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) researchers from North Carolina State University were involved in a national nanotechnology research effort to develop self-powered devices to help people monitor their health as well as understand how their immediate environment affects it. Their efforts were funded by a five-year NSF grant of $18.5 million. The funding is renewable for an additional five years.

Self-powered wearable sensors to monitor human health. Video courtesy of North Carolina State University.

Self-powered sensors could enable 24-hour monitoring of blood sugar, heart rate, or other biomedical data via a device that can be worn on the arm of a patient or the leg and powered by the body’s temperature.

Self-powered sensors could similarly be used to monitor the warm exhaust gases in flues of a chemical plant, or even air quality in the ducts of a heating and ventilation system.

Conclusion

Self-powered sensors have immense potential for application in various fields. They will help reduce inconvenience in many basic applications from changing batteries to making life easier for patients requiring continuous as well as periodic medical observation.

References

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