Transistors with tunable transconductance allow high-quality recordings of human brain rhythms.

An organic electrochemical transistor operates in accumulation mode with high transconductance. The channel comprises a thiophene-based conjugated polyelectrolyte, which is p-type doped by anions injected from a liquid electrolyte upon the application of a gate voltage. The use of ethylene glycol as a co-solvent dramatically improves the transconductance and the temporal response of the transistors.

Organic electrochemical transistors are integrated on depth probes to achieve localized electrical stimulation of neurons. The probes feature a mechanical delamination process which leaves only a 4 μm thick film with embedded transistors inside the brain. This considerably reduces probe invasiveness and correspondingly improves future brain-machine interfaces.