Cellulose for Light Manipulation: Methods, Applications, and Prospects

Abstract

The colors of plants and animals can be achieved by different interactions of light with matter. [10][11][12][13][14][15][16][17] Animals or plants use the biological system colors as warning, for camouflage, or for signaling. Coloration can be generated by the selective absorption of light from the visible range of the spectrum by using pigments (pigmentary colors), which are absorbing subsets of the visible spectrum and transmitting and reflecting the other parts of the visible light. Therefore, the tissue occurs in the color of the wavelength of the reflected radiation. This is used for example by flowers of plants as a signal, because they have to stand out against the background of the vegetation in order to attract pollinating insects. Therefore, they appear in bright colors by reflecting certain wavelengths of visible light, which are then perceivable for the pollinating insects as well as for humans. [10][11][12][13] However, light-matter interaction with respect to absorption is of general importance, but will not be further discussed in this review. On the other hand, coloration can be created by coherent or incoherent scattering of light on highly structured and unstructured tissues (structural colors) in the range of the wavelength of incident light. Here, different wavelengths of light are selectively reflected from a structure and the remaining wavelengths can then be transmitted or absorbed. [10][11][12][13][14][15] These biological photonic sub-micrometer structures yield a distinct coloration through the creation of a refractive index contrast between the used materials. This is an interesting fact, because natural systems cannot be built on high-refractive index inorganic materials, which are commonly used in contemporary technology. Instead, nature makes use of biopolymers such as keratin, chitin, collagen, and cellulose. However, all of these biopolymers exhibit a refractive index around ≈1.5. In order to be able to create bright structural colors, a high refractive index contrast is required. Therefore, nature is using air voids to create the necessary refractive index contrast (Δn ≈ 0.5). Alternatively, nature can also use melanin with a refractive index of about 2 and keratin in mixed composites or by using anhydrous guanine with a refractive index of 1.83, whose crystal arrangements are responsible for the metallic luster of many fish. [15,16] Pigmentary color as well as structural color can also occur in combination (combined colors). All of these aspects can also be separated in iridescent or noniridescent colors. [10,15] Birds, like the Panama Amazon parrot (Amazona ochrocephala panamensis) or the kingfisher (Alcedo atthis) are using different combinations of pigments and sub-micrometer structured components.Cellulose is one of the most abundant biopolymers on earth. It is a sustainable and renewable raw material with many beneficial properties. Due to its availability, nontoxicity, environmental friendliness, biocompatibility, and biodegradability, cellulose is one of the world's most ...

Methylcellulose–Cellulose Nanocrystal Composites for Optomechanically Tunable Hydrogels and Fibers

“…Potential applications for advanced cellulosic materials include: biomedicine, tissue engineering, photonics, smart materials, emulsions, foaming, and sensors [ 13 , 14 , 15 , 16 , 17 ]. The rich history and applications of cellulose and various cellulose-based materials and nanocomposites are evident from several excellent reviews [ 4 , 5 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Yet, there are numerous properties and potential applications of celluloses, nanocelluloses, and their composites that remain unexplored.…”

“…Yet, there are numerous properties and potential applications of celluloses, nanocelluloses, and their composites that remain unexplored. Especially, the trend towards sustainably produced optical and optoelectronic materials and devices has recently gained attraction, and cellulose derivatives and their composites appear as key components [ 20 ].…”

Nanocellulose‐Based Functional Materials: From Chiral Photonics to Soft Actuator and Energy Storage

“…Owing to their chiral liquid crystal (LC) nanostructures, CNCs are increasingly used in chiral photonics to produce a range of fascinating functional materials with brilliant structural colors (Figure 1f). [19,[52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] Interestingly, bioinspired nanocellulose-derived smart materials have recently been investigated for the development of soft actuators and soft robotics (Figure 1g). Nanocellulose-based soft actuators with tailorable and programmable properties can respond to external stimuli, such as humidity, temperature, pH, light, and magnetic/electric fields.…”

Methylcellulose-Cellulose Nanocrystal Composites for Optomechanically Tunable Hydrogels and Fibers

“…[13][14][15][16][17] The rich history and applications of cellulose and various cellulose-based materials and nanocomposites are evident from several excellent reviews. [4,5,[18][19][20][21][22][23][24] Yet, there are numerous properties and potential applications of celluloses, nanocelluloses, and their composites that remain unexplored. Especially the trend towards sustainably produced optical and optoelectronic materials and devices has gained attraction recently, and therein cellulose derivatives and their composites appear as key components.…”

“…Especially the trend towards sustainably produced optical and optoelectronic materials and devices has gained attraction recently, and therein cellulose derivatives and their composites appear as key components. [20] Here, this review focuses on the recent findings on the optomechanical properties of methylcellulose (MC), a commonly used cellulose derivative and its composites with cellulose nanocrystals (CNCs). We first provide a brief introduction to methylcellulose and cellulose nanocrystals and their properties.…”