Fig. 7: Experimental and numerical simulation setup for capturing geometry changes in microfluidic devices due to transport and chemical reactions.

Red arrows denote the flow of SrCl₂, blue arrows denote the flow of Na₂SO₄, and purple arrows indicate the observation process. a Experimental setup consisting of an optical microscope, a syringe pump injecting 50 mM SrCl₂ and 50 mM Na₂SO₄ at 50 μL/min for the chip with rock pattern and 1000 nL/min for the chip with uniform pattern, the microfluidic devices, and the outflow³. b Transport of SrCl₂ and Na₂SO₄ within the borosilicate glass chip, referred to as the chip with rock pattern. The dashed box marks the region where SrCl₂ diffuses from the top and Na₂SO₄ from the bottom. c Transport of SrCl₂ and Na₂SO₄ within the polydimethylsiloxane (PDMS) chip, referred to as the chip with uniform pattern. The dashed box marks the region where SrCl₂ diffuses from the top and Na₂SO₄ from the bottom. d Preparation for Lattice–Boltzmann simulations, in which images of the snapshot region are acquired at multiple time steps and subsequently segmented. e For each segmented image, a multi-component Lattice–Boltzmann simulation is performed using boundary conditions consistent with the experimental setup, and f A Lattice–Boltzmann simulation with a conservative tracer is also performed using fixed boundary values of 1.0 mM at the top and 0.0 mM at the bottom, from which effective diffusivity is derived. The same numerical setup is applied to the PDMS experiments.