Facile Laser-Cutting Process for Nanocellulose-Paper-Based Microfluidic Microchannel Fabrication

Nanofibrillated cellulose paper (nanopaper) has drawn increasing attention as a potential material for various areas, due to its extremely smooth surface, excellent optical transparency, and sequent nanofiber matrix. To extend nanopaper application as the analytical platform, nanopaper-based microfluidics has quickly advanced recently. However, the current method of patterning microchannels on nanopaper, which is the basic for establishing microfluidic (i.e., 3-D printing and spray coating), still has some limitations, including low precision and long preparation time. So, in this study, we utilized laser cutting to fabricate microchannel patterns on nanopaper by burning the surface of nanopaper. Through systematic parameters (laser-cutting speed and power) optimization, we identified the optimal laser-cutting conditions, enhancing both efficiency and accuracy. The minimum depth and width of the microchannels were reduced to 15 and $58~\mu $ m, respectively. The entire fabrication process, including drying, was completed in less than 35 min. Compared to the existing methods, this method has smaller microchannels size, time saving, and no need for additional molds or equipment those advantages, which contribute its novelty and accuracy. By arranging different shapes of lines, microchannels for various sensing were developed. As a proof of concept, we developed two functional nanopaper-based analyzer devices (NanoPADs). With a detection limit of 2.2 mM for glucose and 281 fM for Rhodamine B (RhB), both demonstrate excellent performance and low detection limits. The results indicate that our laser-cutting nanopaper microchannels may serve as a platform for developing high-performance analytical devices, which may spark the development of nanopaper in the future.