為了更進一步研究纖維素的光子特性並探索其光電應用，相關基礎研究室必須不可或缺的。已知納米纖維素 (CNC) 在水溶液中可表現出膽甾型液晶 (CLC)。我們從以下方面研究了納米纖維素在水溶液的一些物理性質：(1) 觀察納米纖維素水溶液在不同濃度下狀態 (2) 測量及控制螺距 (3) 觀察和控制納米纖維素的分子排列。
納米纖維素在水溶液三種不同的濃度範圍對應了三種不同形態：均質相（低於 4 wt%）、雙相狀態（從 4 到 10 wt%）和完全液晶態（超過 10 wt%）。在雙相狀態下，指紋紋理是膽甾相的典型紋理，可以使用偏光顯微鏡觀察到。可以從指紋紋理中測量 2 到 11 µm 的螺距；然而，當指紋紋理的寬度較窄，當螺距小於2 µm時，使用偏光顯微鏡無法觀察到指紋紋理。此外，我們已觀察到納米纖維素水溶液的蒸發過程顯著影響 CNC 薄膜的虹彩。快速乾燥含有 CNC 的水溶液的液滴呈現出從液滴的邊緣的紅色到中心的藍色。這一觀察結果與典型的咖啡環效應相關。相比之下，緩慢蒸發對納米纖維素水溶液會導致從邊緣到液滴中心的顏色更均勻，其中液滴中水的毛細流動會減少，水會緩慢蒸發，我們可以通過濕度控制蒸發速率獲得大面積的藍色區域，這些觀察結果表明，在我們系統中CNC的結構色是由於熱力學穩定態的螺距顯著受到 CNC 水溶液中水蒸發速率的影響。通過我們的模型，我們假設由溶致液晶 (LC) 的蒸發速率引起的動能阻滯與由熱致液晶和其他材料的溫度變化率引起的動能阻滯相同。

To advance cellulose photonics and explore its optoelectronic applications, fundamental research is intrinsically required. Cellulose nanocrystals (CNCs) in aqueous suspension are known to exhibit the cholesteric liquid crystal (CLC) phase. We investigate some physical properties of CNCs in aqueous suspension in term of (1) observing the dependence of the LC phase on the CNC concentration in aqueous suspension, (2) measuring and controlling the helical pitch, and (3) observing and controlling the alignment.
Three different concentration ranges were identified: the isotropic phase (below 4 wt%), biphase regime (from 4 to 10 wt%), and fully liquid crystalline (beyond 10 wt%). In the biphase regime, fingerprint textures, which are a typical texture of a cholesteric phase, are observable using a polarizing microscope. The helical pitch from 2 to 11 µm can be measured from the fingerprint textures; however, when the width of the fingerprint textures is narrower, and thus the helical pitch is shorter than 2 µm, the fingerprint textures cannot be observed using a polarizing microscope. Further, the drying process of the aqueous suspensions has been observed to significantly influence the quality of the iridescence of the CNC films. Rapidly drying a droplet of the CNC-contained aqueous suspension exhibits rainbow colors from red to blue, which can be observed from the edge to the center of the droplet. This observation is correlated with a typical coffee-ring effect. By contrast, slowly drying a counterpart results in more uniform color from the edge to the center of the droplet, and a blue domain over a large area can be attained via humid-controlled drying, wherein capillary flow would be reduced and water gradually evaporates. These observations suggest that the thermodynamically stabilized helical pitch of CNCs, which determines the structural colors in our systems, is significantly influenced by the rate of water evaporation from the CNC aqueous suspensions. Through modeling, we hypothesize that kinetic arrest induced by the evaporation rate of lyotropic liquid crystals (LCs) would be equivalent to that induced by the rates of change in temperature for thermotropic LCs as well as other materials.

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