Inkjet printing of anisotropic structures by cellulose nanocrystals

Cellulose is one of the most promising biopolymer material. According to its high mechanical properties, sensing for electric and magnetic fields, and unique optical properties could be usable for many purposes. For now, a... [ view full abstract ]

Cellulose is one of the most promising biopolymer material. According to its high mechanical properties, sensing for electric and magnetic fields, and unique optical properties could be usable for many purposes. For now, a water suspension of cellulose and its derivatives are suitable to manufacture flexible electronics, paper production, food, and additives in optical and pharmaceutical industries. This work reports about a new way of application CNC dispersion as a transparent ink for hidden patterns printing.
The cellulose microcrystal suspension was prepared according to the method described by Marchessault et al, which is commonly used for preparing nonflocculating cellulose suspensions. 
CNC dispersion form anisotropic structure in a bulk, because of assembling of rod-like shape particles in the hydrodynamic process of CNC colloid drying. Reflected polarized light interference in the dry CNC layer. Difference thickness facilitates changes of the imposition of minimums and maximums of slow and fast rays, that showed an iridescent of CNC layers which is visible only in polarized light. 
Rheological properties of CNC dispersion allow to use it as inks for material printer Fujifilm Dimatix 2831. The final substance which was used to print consist of 1% mass fraction of CNC without any additives to control the rheological properties (viscosity – 2.4 cP, surface tension – 69.8 N/m). Low quantity of solid phase in dispersion dictates used patterns with high dpi because of only with terms of coalescence of drops we can obtain enough thickness of printed layer with strong optical anisotropy. Changing the number of printed layers let us have different colors.
The work was supported by the grant of Russian Science Foundation 16-19-10394.