MIT’s battery-free underwater camera is powered by sound.

While seabed cameras are great for tasks like spotting wildlife, feeding them and taking pictures of them can be a challenge. This is where the new camera developed by MIT comes in handy, as it requires no battery and also transmits its photos wirelessly through the water.

Instead of a battery or a very long power cord, the camera contains a series of transducers on the outside of the camera.

When sound waves from sources such as animals or boats reach one of the transducers, the pressure generated by these waves causes the special materials in the transducer to vibrate. Since these materials are piezoelectric, they produce an electric current in response to vibration. Once sufficient energy is produced and stored in a supercapacitor in this way, it is used for photography.

To keep the power consumption for this task as low as possible, ultra-low power image sensors are used. Unfortunately, these sensors only record grayscale images.

To get around this limitation, each photo is actually made up of three separate exposures: one is taken with red LEDs for illumination, one is taken with green LEDs, and a third is taken with blue LEDs. Although each exposure appears black and white, it shows how the subject reflects light on a wavelength of red, green, or blue. As a result, when all three images are sequentially analyzed and combined, one composite color photograph is obtained.

To wirelessly receive this digital photo, encoded in binary in the form of ones and zeros, a surface-mounted transceiver transmits high-speed sound wave signals through the water to the camera. The module in the camera responds either by reflecting the signal back to the transceiver, which indicates a 1, or by absorbing the signal, which indicates a 0. So by keeping track of which signals are reflected back to the transceiver and which are not, the computer above can record a combination of ones and zeros A representing a photograph.

Associate professor Fadel Adeeb (left) and research associate Walid Akbar (right) with a camera developed by their team. Photo: Adam Glanzman.

The technology currently has a maximum underwater range of 40 meters and has been used successfully for tasks such as documenting the growth of an underwater plant within a week. The MIT team now hopes to increase the camera’s range and storage capacity to the point where it can eventually transmit images in real time and even record full-length video.

An article about the research was recently published published In the magazine nature communication. Photos taken by the camera can be seen in the following video.

Source: MIT.