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Abstract Mineral dissolution in porous media coupled with single- and/or multi-phase flows is pervasive in natural and engineering systems. Dissolution modifies the physical, hydrological, and geochemical properties of the solid matrix, resulting in a complex coupling between local dissolution rate and pore-scale flow. The work reports a microfluidic approach that includes 2D reactive porous media and advanced pore flow diagnostics for the study of pore-scale dissolution in porous media with unprecedented details. The 2D microfluidic porous media, called micromodels, were fabricated in calcite by combining photolithography and wet etching, which not only offers precise control over the structural and chemical properties, but also facilitate unobstructed optical access to the pore flow, significantly improving over existing methods. We believe the work represents the first of its kind as it for the first time directly applies photolithography to calcite samples and demonstrates the use of particle image velocimetry to investigate chemical reactions in porous media. The preliminary results have revealed the crucial roles of local concentration gradients in mineral dissolution and call for reconsideration of many assumptions used in the current modeling tools, which paves the way for renewed fundamental understanding of reactive transport and improved modeling tools with better accuracy. 

This review highlights microfluidics as a disruptive platform for advancing carbon capture and storage, enabling rapid testing, enhanced mass transfer, and precise flow control while offering insight into mechanisms, tools, and design strategies. 

Pressure is important in virtually all problems in fluid dynamics from macro-scale to micro/nano-scale flows. Although technologies are well developed for its measurement at the macroscopic scale, pressure quantification at the microscopic scale is still not trivial. This study reports the design and fabrication of an on-chip sensor that enables quantification of pressure in microfluidic devices based on a novel technique called astigmatic particle tracking. With this technique, thin membranes that sense pressure variations in the fluid flow can be characterized conveniently by imaging the shapes of the particles embedded in the membranes. This innovative design only relies on the reflected light from the back of the microchannel, rendering the sensor to be separate and noninvasive to the flow of interest. This sensor was then applied to characterize the pressure drop in single-phase flows with an accuracy of ∼70 Pa and good agreement was achieved between the sensor, a commercial pressure transducer and numerical simulation results. Additionally, the sensor successfully measured the capillary pressure across an air–water interface with a 7% deviation from the theoretical value. To the best of our knowledge, this pore-scale capillary pressure quantification is achieved for the first time using an on-chip pressure sensor of this kind. This study provides a novel method for in situ quantification of local pressure and thus opens the door to a renewed understanding of pore-scale physics of local pressure in multi-phase flow in porous media.