Axon-Like Wires, Inspired By the Human Nervous System, Amplify Rather Than Degrade Signals

Researchers from Sandia National Laboratories, Stanford University, and Texas A&M University have proposed using a "semi-stable edge of chaos" approach to transmit signals in place of standard wires and circuit traces — attempting to tap into the same operating principles as the axons in a human nervous system to deliver neuromorphic wiring that amplifies its own signals.

"Any electrical signal propagating in a metallic conductor loses amplitude due to the natural resistance of the metal. Compensating for such losses presently requires repeatedly breaking the conductor and interposing amplifiers that consume and regenerate the signal," the researchers explain. "This century-old primitive severely constrains the design and performance of modern interconnect-dense chips1. Here we present a fundamentally different primitive based on semi-stable edge of chaos (EOC), a long-theorized but experimentally elusive regime that underlies active (self-amplifying) transmission in biological axons."

Axons make up the connections between nerve cells in vertebrates, including humans — effectively serving the same function as wires or circuit traces in electronics. Unlike wires, though, there are normally no signal losses over the length of an axon — and it's this self-amplifying property the team are looking to bring into the world of electronics, delivering neuromorphic wiring that doesn't have the same losses as today's simple metals.

Brought to our attention by IEEE Spectrum, the team's work uses a lanthanum cobalt oxide substrate under a metal trace to create a non-linear material that, in certain conditions, can exhibit negative resistance — amplifying, rather than degrading, the signal as it travels the length of the wire. Testing shows promise: in the team's experiments, the axon-like wire delivered a signal at its far end, which was as much as 70 percent stronger than at the input — amplifying it just like the signals in a human nervous system.

"While superficially resembling superconductivity," the researchers explain, "active transmission offers controllably amplified time-varying small-signal propagation at normal temperature and pressure, but requires an electrically energized EOC medium. Operando thermal mapping reveals the mechanism of amplification: bias energy of the EOC medium, instead of fully dissipating as heat, is partly used to amplify signals in the metallic line, thereby enabling spatially continuous active transmission, which could transform the design and performance of complex electronic chips."

The team's work has been published in the journal Nature under open-access terms.