"True ease in writing comes from art," wrote Alexander Pope in the early 18th century. Three hundred years on, however, we might get a little extra help from science—thanks to researchers who have been studying how ink flows from pen to paper. Performing theoretical calculations first, the team devised equations for predicting the spreading of ink from a moving pen. The calculations indicated that there is a balancing act between the roughness of paper, which determines the attraction or "surface tension" driving ink flow, and the ink's friction, or viscosity. To confirm that the math held up in the real world, the researchers performed experiments using an idealized, ink-filled tube as a pen and a fine grid of silicon micropillars as a writing surface. The results, due to be published later this month in Physical Review Letters, could be used in the design of better quality paper—or even surfaces that repel ink altogether. Graffiti artists, watch out.
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