Motion of a spherical particle under the influence of osmotic forces

One of the basic mechanisms through which biological cells preserve the consistency of their structure is the regulation of material exchange between cell and surrounding medium. The regulation is performed by a thin semipermeable membrane surrounding the cell; it passes some materials freely, while allowing only slight transmission of others, or completely blocking passage. Water shows the maximum penetrating power. If there exists on both sides of the membrane an aqueous solution of some material which does not penetrate the membrane, then under the influence of osmotic pressure water flows into that region where the material concentration is higher, as long as the difference in hydrostatic pressure does not suppress the motion [1, 2]. The viscous flow which develops may lead to displacement of a particle.