Which type/types of pen uses/ use capillary action in addition to gravity for flow of ink ?

Fountain pens operate through a combination of gravity and capillary action. Gravity pulls the ink from the reservoir toward the nib, while capillary action ensures a controlled, consistent flow through the narrow channels of the feed and the slit of the nib onto the paper. This mechanism allows fountain pens to write smoothly with minimal pressure. In contrast, ballpoint pens primarily rely on gravity to force thick, oil-based ink onto a rotating ball. While some sources suggest minor capillary effects in the way ink adheres to the ball, the standard scientific distinction in pen mechanics identifies the fountain pen as the primary device utilizing capillary action to overcome gravity and regulate flow. Gel pens use a water-based gel with high viscosity that thins under shear stress, but the fountain pen remains the classic example of capillary-driven ink delivery.