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Unconventional shale or tight oil/gas reservoirs that have micro-/nano-sized dual-scale matrix pore throats with micro-fractures may result in different fluid flow mechanisms compared with conventional oil/gas reservoirs. Microfluidic models, as a potential powerful tool, have been used for decades for investigating fluid flow at the pore-scale in the energy field. However, almost all microfluidic models were fabricated by using etching methods and very few had dual-scale micro-/nanofluidic channels. Herein, we developed a lab-based, quick-processing and cost-effective fabrication method using a lift-off process combined with the anodic bonding method, which avoids the use of any etching methods. A dual-porosity matrix/micro-fracture pattern, which can mimic the topology of shale with random irregular grain shapes, was designed with the Voronoi algorithm. The pore channel width range is 3 μm to 10 μm for matrices and 100–200 μm for micro-fractures. Silicon is used as the material evaporated and deposited onto a glass wafer and then bonded with another glass wafer. The channel depth is the same (250 nm) as the deposited silicon thickness. By using an advanced confocal laser scanning microscopy (CLSM) system, we directly visualized the pore level flow within micro/nano dual-scale channels with fluorescent-dyed water and oil phases. We found a serious fingering phenomenon when water displaced oil in the conduits even if water has higher viscosity and the residual oil was distributed as different forms in the matrices, micro-fractures and conduits. We demonstrated that different matrix/micro-fracture/macro-fracture geometries would cause different flow patterns that affect the oil recovery consequently. Taking advantage of such a micro/nano dual-scale ‘shale-like’ microfluidic model fabricated by a much simpler and lower-cost method, studies on complex fluid flow behavior within shale or other tight heterogeneous porous media would be significantly beneficial. 

This systematic study investigates the optical properties and process−structure−property relationships of Mn‐doped zinc oxide (ZnMnO) grown by metal‐organic chemical vapor deposition with varying Mn‐doping concentration and growth conditions. ZnMnO exhibits a good crystal quality oriented in the (002) direction and contains intermixtures of zinc oxide (ZnO)‐like and manganese oxide (Mn_xO_y)‐like phases. The material exhibits a direct energy absorption band‐edge and a reduction in bandgap with Mn‐doping. Photoluminescence studies show that Mn‐doping can simultaneously tailor broad green band luminescence and ultraviolet edge emissions. Post‐growth air‐annealing results in broad Mn_xO_y‐related photoluminescence emissions at 3.3–4.5 eV. A further reduction in the absorption band‐edge is also observed with annealing. Results indicate that luminescence wavelengths and intensities, and absorption band‐edge can be tuned with the Mn‐doping process. This paper promotes a thorough understanding of defect centers in ZnO with transition metal doping and their interrelation with optical characteristics. The work provides a solid foundation for the development of optoelectronic devices, such as light emitting diodes, solar cells, lasers, and photodetectors using ZnO‐based materials.