Biomedical and electrical engineers at UNSW Sydney have developed a new way to measure neural activity using light — rather than electricity — which could lead to a complete reimagining of medical technologies like nerve-operated prosthetics and brain-machine interfaces.
Professor François Ladouceur, with UNSW’s School of Electrical Engineering and Telecommunications, says the multi-disciplinary team has just demonstrated in the lab what it proved theoretically shortly before the pandemic: that sensors built using liquid crystal and integrated optics technologies — dubbed ‘optrodes’ — can register nerve impulses in a living animal body.
Not only do these optrodes perform just as well as conventional electrodes — that use electricity to detect a nerve impulse — but they also address “very thorny issues that competing technologies cannot address,” says Prof. Ladouceur.
“Firstly, it’s very difficult to shrink the size of the interface using conventional electrodes so that thousands of them can connect to thousands of nerves within a very small area.
“One of the problems as you shrink thousands of electrodes and put them ever closer together to connect to the biological tissues is that their individual resistance increases, which degrades the signal-to-noise ratio so we have a problem reading the signal. We call this ‘impedance mismatch’.
“Another problem is what we call ‘crosstalk’ — when you shrink these electrodes and bring them closer together, they start to talk to, or affect each other because of their proximity.”
But because optrodes use light and not electricity to detect neural signals, the problems of impedance mismatch is redundant and crosstalk minimised.
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