Magnetically actuated liquid crystals are potential alternatives to conventional liquid crystal systems in many applications thanks to their advantages of electrodeless operation, remote control, and low cost. However, their practical uses face a major challenge, namely the strong optical absorption of the magnetic components, which are mostly iron oxide-based materials. Here, we overcome this challenge by developing a nanocomposite composed of rod-shaped cellulose microcrystals with magnetite nanoparticles attached to their surfaces. This design takes advantage of the optical transparency and birefringence of the cellulose microcrystals, as well as their anisotropic shape which allows their efficient orientational alignment when their surfaces are modified by magnetite nanoparticles. Only a minimum amount of magnetite nanoparticles is required to enable instant and reversible orientational control of the cellulose microcrystals, ensuring a high degree of transparency of the system. These unique nanocomposites can be fixed in a polymer matrix with defined orientations at different regions by combining magnetic alignment and photolithography processes, producing thin films that appear near-transparent under the illumination of normal light and display patterns with high contrast when sandwiched between cross polarizers. This work reveals the enormous potential of the magnetic assembly strategy and making it a promising candidate for anti-counterfeiting applications.

由于其无电极操作，远程控制和低成本的优点，因此在许多应用中，磁驱动液晶是传统液晶系统的潜在替代品。然而，它们的实际使用面临着主要挑战，即磁性成分的强光吸收性，这些磁性成分主要是基于氧化铁的材料。在这里，我们通过开发一种纳米复合材料克服了这一挑战，该复合材料由棒状纤维素微晶组成，其表面附着有磁铁矿纳米颗粒。这种设计利用了纤维素微晶的光学透明性和双折射性以及它们的各向异性形状的优势，当它们的表面被磁铁矿纳米颗粒改性时，它们的各向异性形状使它们能够有效地取向。仅需要极少量的磁铁矿纳米颗粒即可对纤维素微晶进行即时和可逆的取向控制，从而确保系统的高度透明性。这些独特的纳米复合材料可以通过结合磁对准和光刻工艺，在不同区域以固定的方向固定在聚合物基质中，从而产生在普通光的照射下几乎透明的薄膜，并且当夹在交叉偏振片之间时显示出具有高对比度的图案。这项工作揭示了磁性组装策略的巨大潜力，使其成为防伪应用的有希望的候选者。这些独特的纳米复合材料可以通过结合磁对准和光刻工艺，在不同区域以固定的方向固定在聚合物基质中，从而产生在普通光的照射下几乎透明的薄膜，并且当夹在交叉偏振片之间时显示出具有高对比度的图案。这项工作揭示了磁性组装策略的巨大潜力，使其成为防伪应用的有希望的候选者。这些独特的纳米复合材料可以通过结合磁对准和光刻工艺，在不同区域以固定的方向固定在聚合物基质中，从而产生在普通光的照射下几乎透明的薄膜，并且当夹在交叉偏振片之间时显示出具有高对比度的图案。这项工作揭示了磁性组装策略的巨大潜力，使其成为防伪应用的有希望的候选者。