Abstract: Objects are protected against deposition of fluid-borne particles in a diameter range of from one-hundredth of a micron to several microns from a convection boundary layer flow, by establishing a temperature difference between surfaces of these objects and fluid adjacent thereto such that the temperature of these surfaces is higher by not more than 10K than that of the adjacent fluid, to such an extent that the thermophoretic effect dominates the combined effects of Brownian motion and gravitational deposition of the particles in the boundary layer flow. Highly advanced articles of manufacture are produced when those surfaces are changed structurally, such as during manufacture of integrated circuits, while the thermophoretic effect dominates the latter combined effects.