New Sensor Could Provide More Oceanic Data
Jeffrey Heimgartner posted on August 30, 2019 |

While the Earth’s oceans may cover more than 70 percent of the planet, nearly 80 percent of it is still unexplored. A team of researchers from MIT believe they may have discovered a new system that could become a sort of oceanic “Internet of Things (IoT)” to transmit data via a self-powered, battery-free underwater system.


Faced with the dilemma of how to have a constant power supply without littering the ocean with batteries, the team looked to existing tools used in the realm of technology to create a new sensor. The team focused on two tools: the Piezoelectric Effect, the ability of some materials to produce an electrical charge, and backscatter, a method used to transmit data by reflecting signals back in the direction from where they came.



MIT researchers developed a battery-free underwater sensor that transmits data by absorbing or reflecting sound waves back to a receiver while also storing energy. (Image courtesy of MIT.)
MIT researchers developed a battery-free underwater sensor that transmits data by absorbing or reflecting sound waves back to a receiver while also storing energy. (Image courtesy of MIT.)



In the team’s network system, a piezoelectric sensor with stored data receives acoustic waves of data via a transmitter. As the waves hit, a vibration occurs that creates the needed electrical change. The sensor uses that energy to reflect data back to the receiver. If there is data, it is reflected as a 1. If there is not a reflected wave, it transmits as 0.


“Once you have a way to transmit 1s and 0s, you can send any information,” said coauthor Fadel Adib, assistant professor at the MIT Media Lab and the Department of Electrical Engineering and Computer Science and founding director of the Signal Kinetics Research Group. “Basically, we can communicate with underwater sensors based solely on the incoming sound signals whose energy we are harvesting.”


Adib, along with coauthor researcher JunSu Jang, created the system with a central submerged node, a circuit board to house a piezoelectric resonator, an energy-harvesting unit, and a microcontroller. A separate transmitter is positioned away from the sensor. The researchers tested their system in the MIT pool to collect data on temperature and pressure. The system transmitted 3 kilobytes per second simultaneously from two sensors positioned 10 meters from the receiver with accurate results.



Beyond the potential to gain impressive data on climate change sea temperatures and long-term monitoring of marine-life and brine pools on the Antarctic shelf, the applications could very well work outside of Earth’s atmosphere, such as subsurface ocean data collection on Saturn’s largest moon, Titan.


“How can you put a sensor under the water on Titan that lasts for long periods of time in a place that’s difficult to get energy?” Adib asked. “Sensors that communicate without a battery open up possibilities for sensing in extreme environments.”


The researchers are ready to take the next steps in experimenting with their system in sea waters and testing just how far apart the sensors can be placed and how many sensors can work simultaneously. They hope to eventually explore the system’s ability to transmit images and sounds.


Interested in more innovations to explore oceanic unknowns? Check out Autonomous Underwater Vehicle Maps Ocean Plankton.


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