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.