Numerical simulation of catalytic enhancement in wall-coated enzyme-catalyzed micro-channel via geometric design

Abstract

Microfluidics is widely used in enzyme biotechnology. Wall-coated immobilized enzyme micro-channels (W-IEMRs) offer significant advantages in stability and hydrodynamic performance but have limited catalytic efficiency due to long diffusion paths in the microreactor. This study used a computational fluid dynamics (CFD) model to simulate flow fields and concentration distributions in serpentine micro-channels, quantifying mixing efficiency via the mixing index (MI) and Dean number (De). By testing channels with different curvature radius, bending ratios, and inner diameters, the geometry was optimized to enhance mass transfer and mixing. Simulations showed that a smaller curvature radius, larger bending ratio, and smaller inner diameter strengthen Dean vortices, improving mixing. However, catalytic efficiency has a non-monotonic relationship with these parameters: a curvature radius below 6.31 mm reduces enzyme-substrate contact due to excessive vortices, while a bending ratio exceeding 60 % leads to uneven substrate distribution caused by counter-rotating vortices in adjacent sections, impairing performance. Optimal design parameters are: curvature radius 6.31 mm, bending ratio 60 %, inner diameter 0.5 mm. For micro-channels with varying reaction kinetics, careful consideration must be given to balancing mass transfer and catalytic performance.