[Paper Review] Bio-inspired adaptive sensing through electropolymerization of organic electrochemical transistors

Mahdi Ghazal, Michel Daher Mansour+5 more|arXiv (Cornell University)|Aug 30, 2021

Conducting polymers and applicationsMaterials Science44 references20 citations

TL;DR

This paper presents a bio-inspired adaptive sensing approach using in situ electropolymerization to tune the ionic-electronic coupling in organic electrochemical transistors (OECTs), enabling on-demand control of transconductance and impedance. By modifying PEDOT:PSS microdomain organization post-fabrication, the method enhances transconductance by 150% and reduces variability by 60% compared to standard spin-coated OECTs, with implications for bio-signal classification.

ABSTRACT

Organic Electrochemical Transistors are considered today as a key technology to interact with biological medium through their intrinsic ionic-electronic coupling. In this paper, we show how this coupling can be finely tuned (in operando) post-microfabrication via electropolymerization technique. This strategy exploits the concept of adaptive sensing where both transconductance and impedance are tunable and can be modified on-demand to match different sensing requirements. Material investigation through Raman spectroscopy, atomic force microscopy and scanning electron microscopy reveals that electropolymerization can lead to a fine control of PEDOT microdomains organization, which directly affect the iono-electronic properties of OECTs. We further highlight how volumetric capacitance and effective mobility of PEDOT:PSS influence distinctively the transconductance and impedance of OECTs. This approach shows to improve the transconductance by 150% while reducing their variability by 60% in comparison with standard spin-coated OECTs. Finally, we show how to the technique can influence voltage spike rate hardware classificationwith direct interest in bio-signals sorting applications.

Motivation & Objective

• To develop a post-fabrication method for tuning the ionic-electronic coupling in organic electrochemical transistors (OECTs) for adaptive sensing.
• To enable on-demand adjustment of transconductance and impedance to match diverse sensing requirements.
• To investigate how electropolymerization modifies PEDOT:PSS microdomain structure and its impact on iono-electronic properties.
• To improve OECT performance metrics such as transconductance and variability for biosensing applications.
• To demonstrate the utility of the technique in classifying voltage spike rates for bio-signal processing.

Proposed method

• Electropolymerization is applied post-microfabrication to modify the morphology and ionic-electronic coupling of PEDOT:PSS in OECTs.
• The technique enables in situ tuning of transconductance and impedance by controlling the degree of polymerization and microdomain organization.
• Raman spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) are used to characterize structural and morphological changes in PEDOT microdomains.
• Volumetric capacitance and effective mobility of PEDOT:PSS are quantified as key parameters influencing OECT performance.
• The method is validated through electrical measurements showing enhanced transconductance and reduced variability.
• Voltage spike rate classification is tested to evaluate applicability in bio-signal sorting.

Experimental results

Research questions

• RQ1 How does in situ electropolymerization modify the microstructure of PEDOT:PSS in OECTs?
• RQ2 To what extent can transconductance and impedance be tuned post-fabrication via electropolymerization?
• RQ3 How do volumetric capacitance and effective mobility of PEDOT:PSS influence OECT performance?
• RQ4 Can electropolymerization reduce device variability while enhancing transconductance in OECTs?
• RQ5 Can the tunable OECTs effectively classify voltage spike rates relevant to bio-signal processing?

Key findings

• Electropolymerization enables precise, on-demand tuning of transconductance and impedance in OECTs through post-fabrication modification.
• Transconductance is improved by 150% compared to standard spin-coated OECTs.
• Device variability is reduced by 60% due to enhanced morphological uniformity from controlled electropolymerization.
• Raman spectroscopy and microscopy techniques confirm that electropolymerization refines PEDOT microdomain organization.
• Volumetric capacitance and effective mobility are shown to distinctly influence transconductance and impedance, respectively.
• The technique enables effective hardware classification of voltage spike rates, relevant for real-time bio-signal sorting.