3D-Displays Made of Cellulose

Prototype of new multiaxis nanocellulose-oriented films as candidates for new, cheap displays. (Source: U. Osaka)

Researchers at the Institute of Scientific and Industrial Research at Osaka University introduced a new liquid-phase fabri­cation method for producing nano­cellulose films with multiple axes of alignment. Using 3D-printing methods for increased control, this work may lead to cheaper and more environ­mentally friendly optical and thermal devices.

Researchers at Osaka Univer­sity can say that they have found a special 3D-chessboard, with potential appli­cations in advanced optics and inex­pensive smartphone displays. Many existing optical devices, including liquid-crystal displays found in older flat-screen tele­visions, rely on long needle-shaped molecules aligned in the same direction. However, getting fibers to line up in multiple directions on the same device is much more difficult. Having a method that can reliably and cheaply produce optical fibers would accelerate the manu­facture of low-cost displays or even paper elec­tronics – computers that could be printed from biode­gradable materials on demand.

Cellulose, the primary component of cotton and wood, is an abundant renewable resource made of long molecules. Nano­celluloses are nanofibers made of uniaxially aligned cellulose molecular chains that have different optical and heat conduction pro­perties along one direction compared to the another. Now, nano­cellulose was harvested from sea pineapples, a kind of sea squirt. The researchers then used liquid-phase 3D-pattering, which combined the wet spinning of nano­fibers with the precision of 3D-printing. A custom-made triaxial robot dispensed a nanocellulose aqueous suspension into an acetone coagu­lation bath.

“We developed this liquid-phase three-dimen­sional patterning technique to allow for nano­cellulose alignment along any preferred axis,” says Kojiro Uetani. The direction of the patterns could be programmed so that it formed an alter­nating checker­board pattern of vertically- and hori­zontally-aligned fibers. To demonstrate the method, a film was sandwiched between two ortho­gonal polari­zing films. Under the proper viewing conditions, a bire­fringent checker­board pattern appeared. They also measured the thermal transfer and optical retar­dation properties. “Our findings could aid in the development of next-gene­ration optical materials and paper elec­tronics,” says Masaya Nogi. “This could be the start of bottom-up techniques for building sophisticated and energy-efficient optical and thermal materials.” (Source: U. Osaka)

Reference: K. Uetani et al.: Checkered Films of Multiaxis Oriented Nanocelluloses by Liquid-Phase Three-Dimensional Patterning, Nanomat. 10, 958 (2020); DOI: 10.3390/nano10050958

Link: Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan

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