14 DAY TRIAL // Each and every action that we perform, be it a thought or an actual movement of an arm or leg, is done via electrical impulses. These impulses travel through neurons in nerve fibers from head to toe in extremely brief periods of time, a trait that allows us to perform sudden movements, and not experience “lags” between the time when our brain issues a command (we think about moving), and the actual motion. Observations of how electrical signals travel through neural fibers have just become possible, with the development of a new, super slow-motion camera, able to record one million frames per second.
Previous studies determined that electrical impulses traveled through nerves at about 180 kilometers per hour, which is extremely fast for something without an engine. The new camera, which only works in black and white, is able to make out individual signals hurtling through the nerve channels at these high speeds, and has such a resolution that it allows it to film microsecond-long impulses as they go by, in essence. According to the team that constructed the camera, the instrument has an accuracy of about 100 picoseconds. A picosecond is one trillionth (a millionth millionth) of a second.
The “active element” inside the new instrument that allows for these extreme feats of engineering is the array of single-photon detectors, or SPADs, which are all placed in a line. Each of the detectors features its own stopwatch, which acts as a recorder for the time when one of the SPADs gets hit by a photon. It is in these stopwatches that the 100-picosecond delay may be registered, although that doesn't always happen. The camera was developed at the Delft University of Technology in the Netherlands, by a team of scientists led by expert Edoardo Charbon.
The microchip that powers up the slow-motion camera features 1,024 SPADs and stopwatches on it, each of the pair acting like a single-pixel video camera. “No one has operated so many on a single chip before,” Charbon says of his team's accomplishments. “If every pixel was hit by a photon every microsecond, then you could measure 1024 million photons per second – that's one gigameasurement every second,” he adds, saying that this would be the device's maximum resolution. In reality, not many photons collide with the detectors, so the resolution is a lot smaller, NewScientist reveals.