A Nano-Ink for gel pens based on scalable CNC preparation

Abstract: Recently, gel pens have been the most popular writing instrument all over the world because of their excellent writing performance. However, the gel ink of the pen is difficult to manufacture because the composition of the ink is complicated with specific rheological properties and high-stability requirements. This is the first report of an easily manufactured Nano-Ink for gel pens that is based on cellulose nanocrystals (CNCs) grafted to reactive dyes. The obtained Nano-Ink exhibits proper rheological properties and writing performance when the concentration of CNCs in this ink is 5.96%. For the potential commercial application of this Nano-Ink, a method for large-scale production of CNCs is also developed in our laboratory, including pretreatment of raw material with sulfuric acid, purification of the treated cellulosic fiber with ammonium bicarbonate (AH-NH₄HCO₃), and then homogenization. In AH-NH₄HCO₃ method, the “ultrafine fibers” are retained in the presence of NH₄HCO₃ during centrifugation, and the added NH₄HCO₃ is removed by vacuum distillation. The final CNC yield after homogenization is above 90%, which is much higher than that in previous reports, when dissolving pulp as feedstock is treated with 58% sulfuric acid at 55 °C for 45 min. Therefore, the Nano-Ink based on CNCs is promisingly going to commercial production. Graphical abstract: [Figure not available: see fulltext.].