Micro "Hyper-Channels" on Laser-Refined Cellulose Structures.

Controlled liquid transportation is widely applied in both academia and industry. However, liquid transport applications are limited by parameters such as driving forces, precision, and velocity. Herein, a simple laser-refining technology is presented to produce micro "hyper-channels". A cellulose substrate is rendered hydrophobic through silanization and refined with a laser to produce both hierarchical nanostructures and a wettability contrast simultaneously. Such a method enables faster ("hyper"-channel) aqueous liquid transportation (≈25X, 50 mm s -1 ) compared to conventional methods. Complex patterns can be readily produced at different scales with spatial resolution as low as 50 µm. This technique also controls the refining depth on the thin paper substrate. Shallow channels can be fabricated on thin paper substrates that enable fluidic channel-crossover without liquid mixing. With certain parameters, the technique creates "portals" through the substrate, allowing trans-dimensional liquid transportation between two layers of a single sheet of substrate. The fluid throughput can be increased, while also permitting fluidic channel crossover without liquid mixing. By introducing multiple portals, the controlled fluid can transfer trans-dimensionally several times, enabling further fluidic complexity. The real-life utility of the method is demonstrated by creating a trans-dimensional microfluidic device for colorimetric detection.