Imagine a bionic hand that connects directly to the nervous system: the brain controls its movements, and the wearer feels pressure and heat with a mechanical limb. By the way, we are being warned that with the development of photonic sensors, such fantasies are about to become reality.
Existing neural interfaces are based on electronics and metal components that the body can reject. Therefore, Mark Christensen of Southern Methodist University in Dallas (USA) and his colleagues are creating sensors from optical fibers and polymers, which are less likely to cause an immune response, and also are not subject to corrosion.
The sensors are at the prototype stage, and so far, alas, they are too large to be implanted into the body.
The sensors are polymer balls. Each sphere is equipped with an optical fiber that emits a beam of light. It flows inside the transducer in a cunning way, which is called "whispering gallery mode" (whispering gallery mode) in honor of the room of the same name in London's St. Paul's Cathedral, where the sound travels further than usual, because it is reflected from a concave wall.
The idea of the device is as follows: the electric field associated with the nerve impulse affects the shape of the sphere, which, in turn, changes the resonance of light on the inner shell, that is, the nerve actually becomes part of the photonic circuit. The change in the resonance of the light propagating through the optical fiber signals to the manipulator that the brain, for example, wants to move a finger. Feedback is assigned to infrared radiation, which acts directly on the nerve. The light is directed by a reflector located at the end of the fiber.
Hypothetically, the device will be useful not only for those who have lost limbs, but also for patients with spinal cord lesions: sensors and fiber optics will help bypass the inoperative area. But before implanting the sensors, you need to find out where the necessary nerve endings are located: for example, the surgeon will suggest the patient to try to raise the missing arm.
Scientists plan to demonstrate a workable prototype using a cat or dog as an example over the next couple of years. But first, the size of the sensor will have to be reduced from a few hundred to 50 microns. The $ 5.6 million project is funded by the Defense Advanced Research Projects Agency (DARPA) of the US Department of Defense.
