Empowering Microfluidics by Micro-3D Printing and Solution-based Mineral Coating
Fluid-solid interaction in porous materials is of tremendous importance to earth, space, energy, environment, biological, and medical applications. High-resolution 3D printing enables efficient fabrication of porous microfluidic devices with complicated pore-throat morphology, but lack of desired surface functionality. In this work, we propose a novel approach to additively fabricate functional porous devices by integrating micro-3D printing and solution-based internal coating. This approach is successfully applied to create energy/environment-orientated porous micromodels that replicate the µCT-captured porous geometry and natural mineralogy of carbonate rock. The functional mineral coating in 3D-printed porous scaffold is achieved by seeding calcite nanoparticles along the inner surface and enabling in-situ growth of calcite crystals. To realize conformal and stable coating in confined pore spaces, we are able to control the wetting and capillarity effects: i) capillarity-enhanced nanoparticle immobilization for forming an adhered seeding layer; ii) capillary pore-throat blockage mitigation for uniform crystal growth. These transparent micromodels are then used to directly image and characterize microscopic fluid dynamics including wettability-dependent fluid propagation and capillarity-held phase transition processes. The proposed approach can be readily tailored with on-demand-designed scaffold geometry and appropriate coating recipe to fit in many other emerging applications.