The obtained TOCNF hydrogels were de-aired in a planetary centrifugal mixer (THINKY AR-250, JAPAN) and transferred to a syringe (Henke Sass Wolf, 60 mL, Luer lock, soft jet ) and stored at 5 °C overnight. The TOCNF-C hydrogels (2% w/w) were extruded using a syringe pump (CHEMYX, Model FUSION 6000, USA) equipped with a coaxial spinning nozzle (Rame-Hart Instrument CO), ́ using a Gauge 13 for the outer needle with an inner diameter Φe = 1.8 mm. Three inner syringes were used Gauge 21, 19, and 17 corresponding to small, medium, and larger outer diameters, Φi of 0.813, 1.07, and 1.47 mm, respectively. Coagulation in a bath produced HF and, depending on the geometry of the coaxial system, yielded the respective sizes, namely, small, medium, and large HF (HF-s, HF-m, HF-l, respectively). Room temperature (20 °C) was used during spinning, and the coagulation was conducted in an acid bath 0.01 M HCl (HCl ACS reagent, 37%, and Milli Q type I water). The acid bath conditions were selected according to previous experience,10,49,50 which indicated instantaneous coagulation of TOCNF in contact with water at pH = 2 (0.001 M HCl), where protonation of carboxylate groups occurs, reducing the electrostatic repulsion according to Derjaguin−Landau−Verwey−Overbeek theory (DLVO).50 This condition leads to the diffusion of water from the extruded nanocellulose hydrogel, drawing the fibrils together and leading to their solidification as a filament.
By: Reyes, Guillermo; Ajdary, Rubina; Yazdani, Maryam R.; Rojas, Orlando J.