Ballpoint/Rollerball Pens: Writing Performance and Evaluation

Here, a brief history of the development of the ballpoint/rollerball pen and the fountain pen is presented. Their principle of operation is analogous that of multipart microfluidics-type devices, where capillarity-gravity drives the ink, a complex fluid, to flow in the confinement of a micrometer-sized canal or to lubricate a ball rotating in a socket. The differences in the operational writing principles of the fountain pen versus the ballpoint/rollerball pen are discussed. The ballpoint/rollerball pen's manner of writing was monitored using lens end fiber optics and was digitally recorded. The ball rotation rate per unit length was monitored using a piezoelectric disk oscilloscope technique. The role of ink (a complex fluid) chemistry in the wetting phenomenon is elucidated. We also discuss methods for studying and evaluating ink-film-ball-paper surface wetting. The goal of the proposed research is to optimize and improve the writing performance of the ballpoint/rollerball pen.