What does ultrafiltration utilize to achieve movement across a membrane?

Ultrafiltration is a process that uses pressure to move water and small solutes across a semipermeable membrane. This technique is crucial in various medical applications, including dialysis for patients with kidney failure, where it is essential to remove excess fluids and waste products from the blood. The application of pressure facilitates the movement of the solvent (typically water) while filtering out larger solute particles, allowing for effective separation.

In the context of this question, the movement across the membrane is driven purely by the pressure applied to one side of the membrane, which forces the fluid through while retaining larger molecules and particles. This is distinct from other methods that might rely on different physical forces, such as gravity or temperature changes, which do not directly serve the same purpose as the pressure-driven process of ultrafiltration.