MIT Researchers Create Underwater Sensors That Don't Require Batteries

Researchers at MIT have developed a underwater communications system that doesn't require batteries.
Donna Fuscaldo
Floor of the ocean bingokid/iStock

The idea of an under-water system of connected sensors that sends data to the surface just got a little closer to reality thanks to a team of  Massachusetts Institute of Technology scientists.  

The researchers created a battery-free underwater communication system that requires near-zero power to transmit data from sensors. It could be used to study climate change and track the cycles of marine life over a long period of time. 


Underwater Internet of Things requires a power alternative 

The MIT researchers including co-author Fadel Adib, an assistant professor in the MIT Media Lab and the Department of Electrical Engineering and Computer Science and founding director of the Signal Kinetics Research Group, will present the system at the SIGCOMM conference being held this week. 

As it stands, researchers have been stumped on how to supply constant power to an underwater Internet of Things, that would rely on sensors that are designed to stay submerged for long periods of time.

Researches relied on the piezoelectric effect and the backscatter to create the system

In order to develop a system that requires little in the way of power, the MIT researchers turned to two key phenomena: the piezoelectric effect and the backscatter.

The piezoelectric effect happens when vibrations in certain materials generate an electrical charge while backscatter is a technique used in RFID tags to send data by reflecting it off a tag. With the system, a transmitter sends acoustic waves through the water to a senor that stores the data. Because it is piezoelectric, when the water hits the sensor it vibrates and stores the electrical charge that is created. That stored energy is then reflected from the sensor back to a receiver. The back and forth between the sensor and receiver corresponds into the bits in the data. 

“Once you have a way to transmit 1s and 0s, you can send any information,” said Adib in a news release highlighting the results. “Basically, we can communicate with underwater sensors based solely on the incoming sound signals whose energy we are harvesting.”

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To demonstrate how the system dubbed the Piezo-Acoustic Backscatter System works, the MIT researchers used a pool at the university to gather data such as the temperature of the water.  The system transmitted 3 kilobits per second of data from two sensors simultaneously. The senors and receivers were at a distance of 10 meters apart. 

The system can be used to explore more than the ocean 

Next up, the researchers plan on demonstrating a version of the system that works between farther distances and communicates with multiple sensors at the same time. They see uses for this system beyond monitoring the earth. 

“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?” said Adib, who co-wrote the paper with Media Lab researcher JunSu Jang. “Sensors that communicate without a battery open up possibilities for sensing in extreme environments.”

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