Marc Ferro

High-performance transistors for bioelectronics through tuning of channel thickness

Transistors with tunable transconductance allow high-quality recordings of human brain rhythms. Despite recent interest in organic electrochemical transistors (OECTs), sparked by their straightforward fabrication and high performance, the fundamental mechanism behind their operation remains largely unexplored. OECTs use an electrolyte in direct contact with a polymer channel as part of their device structure. Hence, they offer facile integration with biological milieux and are currently used as amplifying transducers for bioelectronics. Ion exchange between electrolyte and channel is believed to take place in OECTs, although the extent of this process and its impact on device characteristics are still unknown. We show that the uptake of ions from an electrolyte into a film of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) leads to a purely volumetric capacitance of 39 F/cm3. This results in a dependence of the transconductance on channel thickness, a new degree of freedom that we exploit to demonstrate high-quality recordings of human brain rhythms. Our results bring to the forefront a transistor class in which performance can be tuned independently of device footprint and provide guidelines for the design of materials that will lead to state-of-the-art transistor performance.

Controlling Epileptiform Activity with Organic Electronic Ion Pumps

In treating epilepsy, the ideal solution is to act at a seizures onset, but only in the affected regions of the brain. Here, an organic electronic ion pump is demonstrated, which directly delivers on-demand pure molecules to specific brain regions. State-of-the-art organic devices and classical pharmacology are combined to control pathological activity in vitro, and the results are verified with electrophysiological recordings.

A High Transconductance Accumulation Mode Electrochemical Transistor

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.

Localized Neuron Stimulation with Organic Electrochemical Transistors on Delaminating Depth Probes.

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.

Lactate Detection in Tumor Cell Cultures Using Organic Transistor Circuits

A biosensing platform based on an organic transistor circuit for metabolite detection in highly complex biological media is introduced. The sensor circuit provides inherent background subtraction allowing for highly specific, sensitive lactate detection in tumor cell cultures. The proposed sensing platform paves the way toward rapid, label-free, and cost-effective clinically relevant in vitro diagnostic tools.