Highly wrinkled reduced graphene oxide nanocomposite coating for a multiplexed electrochemical biosensor

Nanomaterial-based electronic devices, with dimensions akin to biological molecules and unique chemical attributes, play a pivotal role in various biomedical applications. However, achieving cost-effective and large-scale fabrication of nanomaterial-based thin films while precisely controlling nanostructures poses considerable challenges, hindering their widespread industrial adoption. To address this, we introduce meniscus-guided coating for the fabrication of reduced graphene oxide nanocomposite with high surface area and excellent electroconductive properties in a facile and scalable manner. Using computational fluid dynamics modeling, we systematically analyzed the rheological properties of the solution containing reduced graphene oxide and chitosan, optimizing coating speed conducive to the stable formation of an elongated meniscus. Additionally, we employed in situ high-speed microscopy to observe the solidification kinetics, enabling an understanding of the wrinkle formation mechanism that enhances the overall surface area. Compared to thicker coatings (∼hundreds of nanometers), the optimized nanocomposite exhibited a 62% increase in surface area and a 97% enhancement in electroconductivity. Consequently, a multiplexed biosensor featuring this highly wrinkled thin nanocomposite simultaneously detected three antibodies related to endoplasmic reticulum stress on the same chip without any cross-reactivity: anti-PDIA6, anti-PERK, and anti-GRP78, with limit of detection of 65.94 pg mL⁻¹, 102.58 pg mL⁻¹, 53.90 pg mL⁻¹, respectively. This nanomaterial coating technology holds promise in overcoming barriers that hinder precise control of nanostructures within thin films, facilitating the transition to mass-production of the multiplexed sensors in biomedical fields, such as point-of-care diagnostics and healthcare monitoring.