Ions Power Machine-Human Interface Demo

　　An “inverted” battery that converts electrical signals into the ionic current used by the human brain’s neuron-to-neuron synapses could provide the perfect machine-to-human interface, according to the University of Maryland's NanoCenter, which recently demonstrated an organic prototype using plant fibers to provide the ion channels.

　　By reversing the way a battery provides power — from electricity to ions, instead of from ions to electricity — an artificial synapse to stimulate brain neurons can be constructed to substitute for the Frankenstein-like direct electrical stimulation used today in medical implants such as pacemakers, artificial retinas, and artificial cochleas, the researchers posit. “The inverted battery design uses the ionic current analogous to that inside a conventional battery to interface with biosystems,” Chengwei Wang, assistant research scientist at the University of Maryland, told EE Times. “The signal transferred in neurons involves the transport of ions. Therefore, if combined with artificial synapses, the inverted battery can be used to interface with neurons.”

　　Not only the human nervous system, but every living organism, uses ionic current to communicate and control their internal functions, according to Wang and research partner Liangbing Hu, a University of Maryland professor and principal investigator with the Nanostructures for Electrical Energy Storage Energy Frontier Research Center. The researchers claim that their demonstration, which used the ion channels in a plant to stimulate cultured phosphorescent cells, mimics this universal mechanism using vastly less power than the direct electrical stimulation used today.

　　“Our brain consumes very little power, and I am sure that our direct ion interfacing will need less voltage to generate a specific ion-current compared with electrical stimuli,” Wang told EE Times. The researchers believe the principles demonstrated in their proof-of-concept project can be extended to treat Alzheimer’s disease, clinical depression, and similar disorders before the work moves on to machine-to-man communications. Wang also predicts that the method will provide efficient drug and gene delivery for treating diseases such as cancer.

　　For the NanoCenter experiment, the channels that move nutrients within a blade of grass were filled with lithium ions, which moved from one end to the other when electrically stimulated. The same principle could be applied in artificial synapses filled with ions; electrical stimulation from a circuit would move the ions to the end of the synapse, where the current could pass to a natural synapse connected to a human neuron, yielding an ideal machine-to-human interface. The entire nervous system uses such ionic-current systems to generate electrical fields in each organ. Unlike the direct electrical stimulation used today, whose voltage must exceed a threshold to stimulate a neuron, the generation of ionic currents could be run at nearly any voltage, according to Wang and Hu.

　　The team is currently trying out various ionic conductors using cellulose, hydrogels, and polymers to create ionic cables for artificial synapses. “For the future, we will focus on developing ionic cables with high ionic conductivity, good mechanical strength, and good biocompatibility,” Wang said. The Department of Energy provided funding for the study.