Work

Microfabricated rGO/PANI Interdigitated Electrodes for Reference-Free, Label-Free pH Sensing on Flexible Substrates

Year: 2025

Type: article

Abstract: We present a flexible pH sensor which leverages the unique properties of reduced graphene oxide/polyaniline (rGO/PANI) composite films through an efficient and scalable hybrid microfabrication approach, wherein the rGO/PANI films are conformally coated on flexible polyethylene terephthalate (PET) substrates via dip-coating and thereafter lithographically patterned into precise arrays of interdigitated electrodes (IDEs), serving both as the pH-active medium and the electrical interface. Upon dip-coating, a thermal reduction process is performed to yield uniform rGO/PANI composite layers on PET substrates, where the PANI content is adjusted to 20% to optimize conductivity and protonation-driven response. Composition optimization is first performed using inkjet-printed silver (Ag) contacts and a conductometric readout mechanism is employed to explore pH-dependent behavior. Subsequently, IDE arrays are defined in the rGO/PANI using photolithography and oxygen-plasma etching, demonstrating clean pattern transfer and dimensional control on flexible substrates. Eliminating separate contact metals in the final design simplifies the stack and reduces cost. A set of IDE geometries is evaluated through I-V measurements in buffers of different pH values, revealing a consistent, monotonic change in electrical characteristics with pH and geometry-tunable response. The present study demonstrated that the most precise pH measurement was achieved with an 80:20 rGO/PANI composition within the pH 2-10 range. These results establish rGO/PANI IDEs as a scalable route to low-cost, miniaturized, and mechanically compliant pH sensors for field and in-line monitoring applications.

Source: Micromachines

DOI: 10.3390/mi16121337

Authors: Maryam Sepehri Gohar, Ekin Asim Ozek, Melih Can Tasdelen, Burcu Arman Kuzubasoglu, Yaser Vaheb, Murat Kaya Yapici

Institutions: Sabancı Üniversitesi, École Polytechnique Fédérale de Lausanne, University of Washington

Language: English

Topic: Analytical Chemistry and Sensors

Subfield: Bioengineering

Field: Chemical Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,534

Funders: Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, Türkiye Bilimler Akademisi