A bioelectronic engineer, Klas Tybrandt of Linkoping University in Sweden, has built the first “ion transistor” computer chip, which uses chemical ions and biological molecules as charge carriers instead of electrons. In essence, these ion transistors mean that we can now build computer chips that directly interface with the cells in your body.

In a conventional transistor, there are three terminals: the source, drain, and gate. When current is applied to the gate, electrons flow across the source to the drain — the electrons are the charge carrier. In Tybrandt’s ion transistor, the ionic neurotransmitter acetylcholine is the charge carrier. When the gate is switched on (triggered by a change in “physiological salt concentration”), acetylcholine flows across the transistor. Both inverters and NAND gates have been constructed from these ion transistors, meaning Tybrandt can now manipulate the flow of acetylcholine using any and all logic functions.

Why is this significant? Well, in this case, acetylcholine is the neurotransmitter that activates muscles. When you think about moving your arm, the message travels along your nervous system until it reaches your bicep, where a neuron transmits an acetylcholine ion to a nearby muscle cell. Tybrandt’s ion logic chip could be wired into your nervous system, and take over if something goes wrong — or, in true computer fashion, perhaps the chip could offer a level of muscle accuracy and flexibility that the default human nervous system isn’t capable of. For paralyzed people, this chip might be able to restore lost movement.

This ion logic chip doesn’t just work with acetylcholine, either: many other common neurotransmitters can also act as the charge carrier. In theory, it might be possible to one day implant an ion chip into your brain that monitors levels of epinephrine (adrenaline), and triggers various parts of your brain or the release of other neurotransmitters in response. Perhaps a HUD would pop up your contact lens display asking “You seem to be preparing for fight or flight. Do you wish to cancel this autonomic response? Y/N.” Ditto, it might be possible to have a chip that monitors and reacts to your serotonin levels, effectively acting as a digital anti-depressant.

Now read about MIT’s discovery of the location of memories, or a mind-controlled robot arm

Read more at Nature (paywalled)