The small intestine (SI) exhibits complex surface microstructures, such as villi and protrusions, which are believed to modulate local flow fields and promote the transport and absorption of luminal contents. However, the quantitative relationship between these surface morphologies and the microscopic flow dynamics remains poorly understood due to the intestine's intricate geometry and motion. To elucidate how intestinal microstructures shape near-wall flow fields and promote convective mixing, this study compares dynamic flows in a SI tube and a pseudo–small intestine (PSI) tube, serving as a simplified intestinal model, during contraction motion. The SI and PSI tubes are deformed using air-driven balloon actuators to mimic intestinal motion, and particle tracking experiments are performed to visualize the near-wall flow fields. The particle trajectories in the PSI show a uniform axially aligned motion, whereas those in the native SI exhibit substantial lateral displacement near the wall. Quantitative analysis reveals that lateral dispersion in the SI is approximately 14-fold higher than that in the PSI model, indicating that microscopic wall structures significantly enhance transverse transport. These findings suggest quantitative evidence on how intestinal microstructures shape microscopic flow fields and promote convective mixing.
Komatsu et al. (Sun,) studied this question.