Design of Experiments based Study to Optimize Laster Induced Graphene Surfaces for Electrochemical Sensor Applications

The photothermal interaction of a CO2 laser beam polyimide sheets results in the formation of graphenous surfaces termed as laser-induced graphene (LIG). Although the research and applications of LIG are manifold, there have been certain aspects that require investigation, such as the applicability of laser-induced conductive fibers, which are formed at certain combinations of laser parameters (power, scan rate, resolution). In this work, we aim to investigate the properties of the fibers and its suitability for electrochemical applications. Fourier transform infrared analysis and Raman spectroscopy revealed the existence of oxygen functional groups and defects on the surface. Electrochemical analysis by cyclic voltammetry and impedance spectroscopy concluded their unsuitability as the fibers are loosely bound to the surface and are removed after every cleaning step. Exfoliation by the scotch tape of the LIG surfaces engraved at different laser powers also revealed the removal of these materials after every exfoliation. Hence, to obtain a surface with high conductivity void of fibers, we report for the first time the implementation of DoE based on D-optimal design across the desirable range of laser parameters where LIG was void of fibers. Compared to conventional one-factor-at-a-time experiments, by implementing D optimal design we obtained the best parameters for achieving high performance electrochemical surfaces with very few experiments. The mathematical model for the dependency of output parameters with input included second order polynomial. This research provides fundamental insights on the LIG fibers and also showcases the implementation of time and resource-efficient DoE to obtain the optimal parameters for engraving LIG surfaces.