A rapid and direct CO2 laser ablation method was developed to create superhydrophilic surfaces and arrays of hydrophobic-superhydrophilic patterns for application in bioassays. Here, a combination of superhydrophilic and hemiwicking wetting characteristics was exploited to create microfluidic slides that were used as biological assays that prevented cell aggregation. This feature allowed microscopic analyses to be carried out at the individual cell level. This bioassay enabled control of cell population in localized areas (15 cells cm-2). The device had 84% transparency, allowing direct fluorescence microscopy measurements in transmission mode. High adhesion of aqueous fluids on superhydrophilic areas surrounded by superhydrophobic boundaries provided selective retention and confinement. The adhered droplets maintained retention under 180° substrate tilt. These architectures provided rapid self-partitioning of the liquid into an array of droplets. The hydrophobic-superhydrophilic patterned arrays may have applications in microfluidic bioassays, high-throughput screening, and medical diagnostics.
Keywords: biological assays; cell assays; laser ablation; microfluidics; optics.