Session: 06-04 Neuromorphic Computing

Paper Number: 171945

171945 - Ion-Selective Gating and Synaptic Memory Emulation in Bio-Membrane/oect Hybrid Interfaces 

Monitoring biologically-relevant ions, such as Na⁺, K⁺, Ca²⁺, and Cl⁻, has garnered significant attention in diverse fields, including bioelectronics, health diagnostics, and environmental sensing. To address this demand, various ion-selective material systems incorporating nanoscale ion carriers like valinomycin (selective to K+ ions) have been developed and proven effective in enabling selective ion transport and sensing. In parallel, organic electrochemical transistors (OECTs) made from mixed ionic electronic conductive polymers (e.g., PEDOT:PSS) have emerged in recent years as promising platforms for biochemical sensing and signal processing due to their inherent signal amplification and compatibility with biological systems. The basis for OECT operation stems from the fact that an influx of cations—driven by a voltage difference between the polymer film and the adjacent aqueous environment—changes the electronic conductance of the polymer film, and thereby modulates current flowing between source and drain electrodes in the device. While these changes in transconductance can be quite sensitive in OECTS, they are not selective to specific cations, which could limit their applications where sensing specific species is important.

In this work, we leverage recently published techniques by the Sarles group to assemble a lipid membrane near an OECT polymer surface to create and experimentally test a hybrid ion-selective OECT system that integrates selective ion transport with the signal amplification capability of OECTs. The prototype system specifically employs a valinomycin-doped lipid bilayer membrane interfaced with a PEDOT:PSS thin-film OECT to correlate transmembrane K⁺ ion transport to changes in OECT conductance. Unlike other approaches to make ion-selective membranes using immobile ionophores embedded in a polymer matrix, our system leverages a thin, defect-free biomembrane (~5 nm thick) that allows for valinoymicin to diffuse from one side to the other to mediate K+ electrodiffusion.  As a result, our hybrid membrane-OECT system operates at lower gate voltages (< 200 mV) and exhibits higher baseline resistance (~GΩ), making it efficient for valinomycin-mediated ion transport and selective for primary ions. The valinomycin-doped membrane/OECT hybrid system demonstrates good selectivity for K⁺ ions, and our objective is to evaluate its sensitivity in detecting K⁺ concentrations across physiological ranges (3 mM to 150 mM). Furthermore, we observe selective memory retention under specific experimental conditions, where the gated response persists even after the cessation of electrical stimulation, mimicking biological synaptic behavior. This activity-dependent retention of OECT conductance states highlights its potential for implementing ion-selective neuromorphic functionalities in emerging computing platforms. Overall, this work demonstrates a versatile approach for combining the strengths of organic electronics with the selective ion transport capabilities of bio-membranes, opening avenues for advanced sensing, biomimetic signal processing, and adaptive neuromorphic computing applications.

Presenting Author: Stephen Sarles University of Tennessee

Presenting Author Biography: Andy Sarles is a Professor and the James Conklin Faculty Fellow in the Department of Mechanical, Aerospace and Biomedical Engineering (MABE) at the University of Tennessee, Knoxville. Sarles received a B.S. in mechanical engineering from the University of Tennessee and M.S. and PhD. degrees in mechanical engineering from Virginia Tech. He joined the MABE faculty at University of Tennessee in 2011. Sarles is also the Associate Director for Industrial Relations in the Center for Materials Processing within the Tickle College of Engineering at UTK and holds joint faculty appointments in the departments of Chemical and Biomolecular Engineering (CBE) and Electrical Engineering and Computer Science (EECS). Sarles’ interdisciplinary research interests include engineered smart materials, transport and signaling through biomimetic interfaces and tissue-inspired materials, revealing nanomaterial-membrane interactions, and artificial synapses and neurons for neuromorphic computing. He is a Fellow of ASME and is the recipient of a 2018 NSF CAREER Award, the 2017 Gary Anderson Early Achievement Award from ASME, and a 3M Non-Tenured Faculty Grant.