General 3D microporous structures fabricated with two-photon laser machining

Microporous structures are a common theme in biomedical devices, microfluidics, geology and other fields of study. However because of the complexity and lack of symmetry, it has been difficult to fabricate 3D arbitrary microporous structures with broad-illumination photolithography. We apply two-photon polymerization and femtosecond laser direct-writing techniques to fabricate 3D microporous structures in photopolymers. Three dimensions are built up from 2D patterned-microchannels with random geometry. The height and the width of the features are about 40 mu m and 5 mu m, respectively. We make 3D microchannels with random apertures and obstacles in two layers that allow liquid to flow through multiple random flowpaths. We also fabricate three-layered lattice-like microstructures. In each layer, the height and the width of the walls are about 18 mu m and 2 mu m, respectively. Our current application of these microporous structures is for a fundamental study of internal fluid interfaces in microfluidic systems during imbibition and drainage, using interfacial areas per volume as a measure of internal energy density as a function of saturation and capillary pressure.