Femtosecond laser spatially shaped continuous scanning fabrication of anisotropic microstructures enabling directional liquid transport

In this study, micro structured surfaces with anisotropic liquid flow properties were constructed on silicon substrates via the femtosecond laser spatial shaping technique. Accurate manipulation of the surface morphology, energy density gradient and melt flow behavior was achieved by modulating the spatial phase and energy distribution of the laser beam. The results show that the elliptical gradient spot can flow 1.5 mm within 320 ms for the liquid precursor film because of the significant eccentricity ratio modulation ability, whereas the circular gradient spot and Gaussian spot exhibit medium and low flow rates, respectively. A gradient design of the spot size verifies the linear regulation of the longitudinal size of the structure by the processing parameters. The interpolation length gradient structure confirms the 'on/off' switching mechanism of liquid flow, and the capillary driving force of the 100 μm interpolation structure is 2.3 times greater than that of the 20 μm structure because of deeper grooves and a greater surface energy gradient. This technology offers a strategy for developing microfluidic chips, self-lubricating surfaces, and smart-responsive liquid transport devices. It demonstrates significant potential for efficient directional fluid manipulation in high-inclination conditions.