Abstract
AbstractBiological environments use ions in charge transport for information transmission. The properties of mixed electronic and ionic conductivity in organic materials make them ideal candidates to transduce physiological information into electronically processable signals. A device proven to be highly successful in measuring such information is the organic electrochemical transistor (OECT). Previous electrophysiological measurements performed using OECTs show superior signal‐to‐noise ratios than electrodes at low frequencies. Subsequent development has significantly improved critical performance parameters such as transconductance and response time. Here, interdigitated‐electrode OECTs are fabricated on flexible substrates, with one such state‐of‐the‐art device achieving a peak transconductance of 139 mS with a 138 µs response time. The devices are implemented into an array with interconnects suitable for micro‐electrocorticographic application and eight architecture variations are compared. The two best‐performing arrays are subject to the full electrophysiological spectrum using prerecorded signals. With frequency filtering, kHz‐scale frequencies with 10 µV‐scale voltages are resolved. This is supported by a novel quantification of the noise, which compares the gate voltage input and drain current output. These results demonstrate that high‐performance OECTs can resolve the full electrophysiological spectrum and suggest that superior signal‐to‐noise ratios could be achieved in high frequency measurements of multiunit activity.
Highlights
Introduction transmissionThe properties of mixed electronic and ionic conductivity in organic materials make them ideal candidates to transduce physiological information into electronically processable signals
The organic electrochemical transistors (OECTs) is typically a three-terminal device in which an ionic flux across an organic active layer voltages are resolved. This is supported by a novel quantification of the causes a variation in current between two noise, which compares the gate voltage input and drain current output. These results demonstrate that high-performance OECTs can resolve the full electrophysiological spectrum and suggest that superior signal-to-noise ratios could be achieved in high frequency measurements of multiunit activity
A range of OECT devices were fabricated with the aim to maximize performance in the electrophysiological spectrum
Summary
The substrate material was polyethylene terephthalate (PET), chosen for its flexibility and ability to support PEDOT:PSS without the addition of the crosslinker 3-glycidoxypropyltrimethoxysilane.[17]. The resulting four electrode styles were patterned either with a 200 nm Au layer with 70 nm active layer thickness or 300 nm Au with 35 nm active layer. These combinations were chosen in order to vary the ratio between interconnect and channel resistance. The interdigitated electrodes were connected to characterization equipment either through electrode pads or the array zero-insertion-force connectors. Property Active area [μm2] Surrounding electrode overlap [μm] Device pitch [μm] Channel length [μm] Finger/turn number Finger/spiral length [μm] Finger/spiral thickness [μm] W/L ratio
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