CO₂ laser fabrication of hydrogel-based open-channel microfluidic devices

This study proposed a rapid and low-cost fabrication method for open-channel hydrogel-based microfluidic devices using CO₂ laser ablation. The agarose hydrogel substrate was prepared with agarose gelation in DI water upon microwave heating, then a commercial CO₂ laser system was used for the direct laser ablation of microchannels on the surface of agarose hydrogel substrate, the hydrophilic nature of the microchannels fabricated on hydrogel substrate enables the self-driven of the liquid inside the microchannels with capillary force. The profiles of the laser ablated microchannels on agarose hydrogel substrate with various laser power and scan speed were studied in detail. Due to the loss of water when exposed to the atmosphere, significant deformation of the fabricated microchannels was observed, and the profile change was recorded for 48 h for comparison. An easy-to-access storage method of hydrogel-based microfluidic device in DI water was also proposed in this study. Unlike compact silicon or polymer-based microfluidic devices, the hydrogel is formed by cross-linked polymer chains filled with water, for a better understanding of the diffusion of small molecules into the bulk hydrogel material during fluid propagation inside the microchannel, the Nile red fluorescent was added into the liquid and the diffusion across the hydrogel-based microchannels with time was measured and discussed in this study. Several open-channel agarose hydrogel-based microfluidic devices were fabricated in this study for the demonstration of the proposed fabrication method. The CO₂ laser ablation approach for agarose hydrogel-based microfluidic devices has the advantages of rapid processing time, low-cost, highly biocompatible, and self-driven without pumps and could have wide application potentials in biological and medical fields.