Sending rovers to Mars and spacecraft to the far reaches of the solar system is pretty standard at this point, and we couldn’t be happier because it means scientists are constantly pushing the boundaries of exploration. But, without taking any credit for these remarkable achievements, it’s easy to lose sight of the fact that there’s a whole extraterrestrial world waiting to be explored here on Earth: the hidden world of the oceans.
Up to 95% of the world’s oceans remain uncharted, unobserved and unexplored. Since we can’t really protect what we don’t know, only about 7% of the world’s oceans are designated as Marine Protected Areas (MPAs). Things could stay that way for a long time given the huge challenges and costs of exploring our oceans, unless we develop cost-effective underwater sensing solutions – and some MIT researchers think they have. exactly what we need.
In a new study, researchers at MIT have presented a new underwater camera that is about 100,000 times more energy efficient than any other underwater camera. It has no wires to a power source or battery. Instead, the camera is powered entirely by sound – underwater acoustic energy generated by passing ships, sea life and anything else that can make waves.
As it does not require an external power supply, the device can operate for weeks or even months before needing to be retrieved, and could thus reach inaccessible nooks and crannies of the oceans that are currently unexplored.
The camera takes color photos even in dark underwater environments. It then sends them back to a receiver through the water using sound waves.
“One of the most exciting applications of this camera for me personally is in the context of climate monitoring. We build climate models, but we lack data for more than 95% of the ocean. This technology could help us build more accurate climate models and better understand how climate change is affecting the underwater world,” said Fadel Adib, associate professor in the Department of Electrical and Computer Engineering and director of the Signal Kinetics group at MIT. MediaLab. in a report.
Riding the waves of sound
To generate energy, the camera uses piezoelectric transducers that convert mechanical energy into electricity. Many other devices exploit piezoelectricity. For example, when you speak into your phone’s microphone, the piezo crystals convert the sound energy of your voice into electrical signals that are relayed through the telecommunications or broadband network to communicate.
But the power output isn’t particularly generous, so the MIT researchers had to keep power consumption to a bare minimum. They used ultra-low-power imaging sensors that capture images only in grayscale. This compromise proves to be particularly problematic underwater where there is not much light.
The challenge was overcome by using red, green and blue LEDs simultaneously. When the camera takes a photo, it takes three separate snapshots for each LED light. When the three images are combined in post-processing, a color image can be reconstructed.
“When we were kids in art class, we were taught that we could create any color using three basic colors. The same rules apply to color images that we see on our computers. We just need to red, green, and blue — those three channels — to build color images,” co-author Waleed Akbar said in a statement.
To send the images it takes to the outside world, the camera sends the image data encoded as bits of 1s and 0s to a receiver using underwater backscatter. The way it works is that the receiver constantly sends sound waves through the water to the camera, which reflects those waves back. The camera can switch between absorbing or reflecting sound waves, two states that correspond to 0 and 1 in digital bits.
“This whole process, since it requires only a single switch to convert the device from a non-reflective to a reflective state, consumes five orders of magnitude less power than typical underwater communication systems” , explains Afzal.
So far in testing, the camera has taken high-resolution images of an African starfish with its tiny tubercles clearly visible, plastic bottles floating in a New Hampshire pond, and even monitored the growth of an underwater plant called Aponogeton ulvaceus for a whole week.
Next, the researchers’ goals are to expand the camera’s memory so it can stream real-time video and increase range. At this time, the prototype wireless underwater camera can transmit data up to 40 meters from the receiver. By extending this range, the camera can travel farther and deeper underwater.
The results were reported in the journal Nature Communication.