A facile spinning approach towards the continuous production of aligned nanocellulose films

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 701; p. 134673
• Main Authors: Daghigh Shirazi, Hamidreza, Håkansson, Karl M.O., Abitbol, Tiffany, Vapaavuori, Jaana
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.11.2024
• Subjects: Alignment; Anisotropy; atomic force microscopy; birefringence; carboxyl group; Cellulose films; cellulose nanofiber; Cellulose nanofibril; Cellulose nanofibril film; Cellulose nanofibrils; CNF; comparative study; Continuous production; controlled study; Film alignment; Film production; flow rate; Humidity; Humidity actuation; hydrochloric acid; methyl group; Nanocellulose; Nanocellulose films; nanofabrication; Nanofibers; nanofilm; Optical Properties; Optical transparency; optics; polarization microscopy; Processes; Production; radiation scattering; reproducibility; scanning electron microscopy; Spinning (fibers); suspension; Suspensions (fluids); tensile strength; Thin Films; ultraviolet visible spectrophotometry; Wet Spinning; wet spinning approach; wide angle X ray scattering; X ray scattering; Alignment; CNF; Humidity actuation; Cellulose nanofibril; Optical transparency
• DOI: 10.1016/j.colsurfa.2024.134673
• ISSN: 0927-7757; 1873-4359

In this work, we present an alternative approach to cellulose nanofibril film (CNF) production, taking inspiration from the wet spinning of fibers to wet spin films. During the spinning process, a CNF suspension is injected into a coagulation bath, where the partially aligned CNF network is locked. The CNF alignment of the dry films is then detected by wide angle X-ray scattering (WAXS). The comparison between the ultimate strengths and strengths at breaks of the films produced with different process parameters, including the suspension injection rate, bath pH, and bath flow rate, indicated no significant change in mechanical properties, suggesting a reliable and constant outcome for large-scale film fabrication. Furthermore, the produced films demonstrated high total light transmittance of 93 % at the wavelength of 550 nm, making them suitable for optoelectronic applications. Polarized optical microscopy revealed that even a low degree of CNF alignment can lead to anisotropic optical properties. Moreover, an anisotropic response to humidity was observed, in which the films preferentially bend in the perpendicular direction of the CNF orientation, thus opening a way for humidity-driven actuators. [Display omitted] •A wet-spinning method to produce cellulose nanofibril (CNF) films is developed.•The produced films demonstrate high light transmittance and partial CNF alignment.•The CNF alignment provides an anisotropic humidity actuation.•The wet-spinning approach has potential to continuous/scalable film production.