Substrate-Independent Laser-Induced Graphene Electrodes for Microfluidic Electroanalytical Systems

Laser-induced graphene's (LIG) inherent graphene-like and highly porous characteristics and its simple, scalable, and inexpensive fabrication render it a desirable electrode material for bio- and chemosensors. The best LIG electrodes are made in polyimide foils using a CO2 laser scriber, which unfortunately limits their integration into more sophisticated analytical devices due to polyimide's inertness. The transfer of LIG electrodes onto standard polymer substrates used in microfluidic systems and their use in microfluidic assays were therefore studied and the resulting electrodes characterized morphologically, chemically, and electro-analytically. It was found that a direct pressure-driven transfer produces highly functional transfer-LIG (tLIG) electrodes. tLIG differed from LIG electrodes with respect to a much smoother surface and hence a lower active surface area, a loss of the graphene characteristic Raman 2D peak, and a slight decrease in electron transfer rates. However, their performance in amperometric detection strategies were comparable also when used in adhesive-tapeenabled microfluidic channels for the detection of p-aminophenol. tLIG outperformed LIG electrodes in their ability to be integrated into more advanced microfluidic channel systems made of an all-polymethyl methacrylate (PMMA) substrate for the biosensing detection of alkaline phosphatase, commonly used as a biomarker and as a biosensor amplification system. LIG and tLIG have hence the potential to change electroanalytical sensing in diagnostic systems as their fabrication requires minimal resources, is highly scalable, and allows their integration into simple and, as tLIG, also sophisticated analytical systems.

Automated summary

Laser-induced graphene (LIG) is a desirable electrode material for bio- and chemosensors due to its graphene-like characteristics. The study found that the direct pressure-driven transfer of LIG electrodes onto standard polymer substrates produces highly functional transfer-LIG (tLIG) electrodes which outperformed LIG electrodes in some aspects, especially in more advanced microfluidic channel systems. LIG and tLIG have the potential to change electroanalytical sensing in diagnostic systems with their scalable and easy-to-integrate fabrication process.