THE MORNING
Researchers at the Massachusetts Institute of Technology in the United States have succeeded in developing an autonomous camera that works entirely without batteries and communicates wirelessly, without emitting waves, intended to improve ocean exploration.
This new technology also helps foster the discovery of new marine species and the monitoring of climate change and pollution.
Designed to be ultra-low-power, the underwater camera uses a sound signal from a base station to power itself and transmit data, according to details of the invention published in the journal “Nature Communications”.
To power the camera, it is explained, the device uses a transducer, made with piezoelectric materials, which converts sound waves into electricity. These waves are transmitted through the water from a base station. The power obtained is of the order of a few tens to a few hundreds of microwatts. This energy is stored in a supercapacitor until it reaches the threshold necessary to take or transmit photos.
With such a power supply, the camera must necessarily have a very low power consumption. To obtain color images, the device is equipped with three LED diodes: one red, one blue and one green.
The camera then takes three photos, one with each lighting color. They are then combined to form a single color image. To transmit the photos, the researchers were unable to use an existing underwater communication system. These use at least 50 to 100 milliwatts, or a thousand times the power harvested by the transducers. They reduced consumption to a few nanowatts by using a technique that does not emit any signal: backscattering (or backscattering).
With this method, they managed to transmit data over 40 meters wirelessly and without emissions from the camera. Backscatter relies on the sound signal emitted by the base station which feeds the camera, part of which is naturally reflected back to the source, like a radar.
The device modifies the reflection coefficient of the piezoelectric transducer using two transistors. The base station is equipped with a hydrophone (a microphone that works underwater) to measure the return acoustic signal. It detects variations induced by changes in the reflection coefficient, thus receiving a binary signal. In this way, the camera transmits data at a speed of a few kilobits per second.
For researchers, this invention could be used in many fields, including oceanography, marine biology, climatology or underwater archaeology. They hope to observe the fauna and flora in the oceans and discover new species. The camera could also monitor pollution and the effects of climate change in the oceans.
