Pen

A pen is a mechanical writing instrument designed to apply a fluid medium, typically ink, onto a surface such as paper. Functionally, it converts stored chemical or pigment substances into a controlled flow, allowing for permanent or semi-permanent textual output. The underlying technology involves various mechanisms for ink delivery and control, ranging from capillary action in ballpoint designs to the capillary wicking action used in fountain-style pens. These designs vary to optimize consistency and flow rate, balancing the pressure required for continuous writing with the need to prevent pooling or clogging. The evolution of the pen reflects advancements in material science, focusing on creating durable casings and highly efficient internal components to achieve precise and reliable graphic output.