MIT Engineers Create Wireless, Battery-Free Underwater Camera

(Photo: Adam Glanzman/MIT) Parts of the ocean that have previously gone unexplored might soon become familiar. Engineers at MIT have built a wireless, battery-free underwater camera that uses sound to power deep-sea journeys.

As of now, a majority of the ocean has gone unprobed. Most of the underwater cameras used to investigate this part of the planet are incredibly unwieldy or expensive to operate: They either wire power from a separate vessel, thus limiting their mobility, or they require battery top-offs from crews on ships. Sending divers into hard-to-reach areas is typically a no-go, too, given the extreme amounts of pressure in places like the Mariana Trench and the deepest corners of the Gakkel ridge. Without the help of autonomous equipment, scientists are left to make educated guesses about what could be hidden in these mysterious places.

MIT’s new camera could be exactly the equipment oceanographers and marine biologists need. The engineers started by creating an exterior containing transducers made of piezoelectric materials, or solids that produce electricity under certain mechanical stressors. As sound waves traveling through the water hit the camera, these piezoelectric transducers vibrate, converting mechanical energy into electrical energy. The camera can then use the energy or store it for later.

The camera contains low-power, commercially-available imaging sensors, but on their own, these would only capture grayscale pictures. To keep power consumption low, the engineers installed red, green, and blue LEDs, which allow the camera to capture color images in low light. The camera individually snaps photos of its surroundings using each color LED. Later on, the information from these images can be combined in post-processing to create a single colorful photo.

Three separate photos, each illuminated with a different LED, effectively “stack” to create a single colored photo. (Image: Afzal et al/Nature Communications)

The device uses a process called underwater backscatter to send image data to land. After converting the data to binary, the camera sends it to a receiver, which bounces it through the water and back to the camera. A nearby hydrophone processes which signals are returned and then uses that binary data to reconstruct an image.

Since it doesn’t require an external power source, the camera can operate for weeks at a time. Though deep sea exploration for unknown species first comes to mind, scientists can also use MIT’s camera to measure the health of farmed fish, track ocean pollution, and monitor the impact of climate change on ocean ecosystems. The camera might even pair well with Internet of Things (IoT) devices to enhance various monitoring missions.

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