Well... technically we should say “as long as there is a light source”, but that doesn't change the fact that the camera built by Columbia University is impressive. Its 1,200 photodiodes not only act in a “traditional” way to record images, but also as if they were photovoltaic cells, switching between one function and another depending on light intensity. With the help of an integrated supercapacitor, the camera manages to do without any battery.
The main sensor of a camera has several things in common with a photovoltaic cell. Obviously, technological evolution kept both components separate, but a team of researchers at Columbia University decided to bring them together under the concept of a very special camera. Its resolution is limited, and it can barely capture one image per second, yet this prototype doesn't need batteries to function. In fact, it also lacks traditional charging ports. The network of photodiodes (30 by 40) installed on the PCB works in photoconductive or photovoltaic mode, so we're (in very relaxed terms) dealing with a sort of hybrid between a camera sensor and a mini-cell.
How It Works
Part of the text found in the official announcement explains that the camera has a supercapacitor that recharges almost constantly with the light entering through the lens. The trick here is that the supercapacitor needs a small push, i.e., an external energy source that allows it to reach 2.74 volts. Once the voltage reaches the necessary level, the external source is interrupted. If the scene maintains an average illumination of 300 lux, the camera will produce one image per second indefinitely. With a scene close to 1,200 lux, the supercapacitor can rise to 3.1 volts and operate for more than 20 minutes if its recharging capacity (0 lux) becomes blocked.
Potential Applications
The university has used the term “self-powered” to describe the camera, but I think it's more logical to say that the camera can record without pauses under the right conditions. Fortunately, those conditions are very easy to achieve, which makes the potential of this design enormous. There's a lot of room to miniaturize, optimize the performance of the photodiodes in both modes, and integrate its functions into other products, such as wearable devices, motion sensors, and why not smartphones. Imagine a mobile device that could restore part of its battery through its cameras...
Official announcement: link
