Research on the Influence Mechanism of Interface Properties and Geometric Parameters on Ferrofluid Pumping Behavior...

Ferrofluid pumps, by controlling the morphology and spatial distribution of ferrofluids through an external magnetic field, achieve noncontact driving and the conversion of magnetic energy into fluid mechanical energy, showing potential application in microfluidic systems. However, the synergistic influence mechanism of interfacial friction within the confined space, pump cavity size effect, and ferrofluid filling volume on pumping behavior remains unclear. To address these issues, a variable-parameter magnetically driven ferrofluid pump experimental platform was constructed to investigate the effects of interfacial wettability, pump cavity geometry, and initial filling angle on pumping behavior. Experimental results show that the initial filling angle affects pumping performance by changing the effective magnetic drive volume. In the low-speed range (1-30 rpm), the flow rate difference is small under different filling angles. Under a back pressure of 10 cm H2O, a 40° filling angle increases the starting speed to approximately 10 rpm. In the medium-speed range (40-80 rpm), the flow rate follows the pattern of 50°>45°>40°, and the system has an optimal filling range (45°-50°). Interfacial wettability modulates frictional behavior by altering the spatial structure of ferrofluids. A continuous liquid film structure forms on the PMMA surface, achieving a flow rate of approximately 3500 μL/min at 30 rpm. On the glass surface, a discrete droplet structure forms, reducing the flow rate to approximately 1900 μL/min (about 54% of that of PMMA). The PC surface exhibits a liquid film-droplet mixing state, achieving a trade-off between pumping efficiency and structural stability. Geometric scale affects pumping performance by altering the magnetic driving torque and interfacial constraint strength. A 14 mm pump cavity fails to establish an effective pressure differential, a 24 mm pump cavity increases the flow rate by approximately 20%-40% at low speeds but fails at approximately 700 rpm, while a 19 mm pump cavity can maintain flow at approximately 800 rpm. This study reveals the coupling mechanism between interfacial structural stability, effective magnetic driving volume, and resistance dissipation, providing a control design strategy for microscale thermal management, biomicrofluidics, and other confined space magnetically driven transport systems.