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For the first time, two types of highly anisotropic, highly transparent wood composites are demonstrated by taking advantage of the macro-structures in original wood. These wood composites are highly transparent with a total transmittance up to 90% but exhibit dramatically different optical and mechanical properties.

Wood is a ubiquitous material, widely used in human society, that features naturally abundant, aligned longitudinal cells (e.g., tracheids in softwood and fibers/vessels in hardwood) with diameters of ≈50-1000 µm. Here, the realization of, fine patterns on a wood surface ranging in size from 40 nm to 50 µm by precision imprinting is described. The precision imprinting is enabled by releasing cellulose fibril aggregates from the bondage of lignin through the delignification process, then imprinting in wet condition and fixing the designed configuration in the dry state. Various precision structures on a wood surface using imprinting technology, including dot arrays, lines, triangular features, and other complex patterns, are successfully demonstrated. Even multiscale structures with nanosized lines on the surface of micrometer hemiballs can be acquired. As a proof of concept, the use of surface-imprinted wood as a microlens array (MLA), which exhibits superior imaging ability and thermal stability even at a high temperature up to 150 °C compared with traditional polystyrene MLA, is demonstrated. This precision imprinted wood may open new possibilities toward environmentally friendly devices and applications in optics, biology, electronics, etc.

method to prepare high-quality monolayer square-lattice colloidal crystals has not been reported yet. In this Communication, we report our study of self-assembly of colloidal polystyrene (PS) spheres on a 1D-patterned substrate. Previous studies showed that colloidal structures formed on a 1D-patterned substrate are highly sensitive to the ratio between sphere diameter (d) and groove period (p). [10a] Here, we explore other factors that could have a key influence on the formation of 2D square symmetric colloidal crystals using a 1D-patterned substrate. By introducing an experimental cell that allows simultaneous actions and strong competition of forces on colloids exerted by the suspension drying front and the patterned substrate, we have identified distinct effects of convective assembly on the growth of colloidal crystal by controlling the angle orientation (a) between the colloidal suspension drying front and 1D template grooves. We find that those experimental configurations with a having a large deviation from a = 45° will introduce a large amount of defects during the self-assembly process. We demonstrate that, by controlling the angle a in the vicinity of 45°, convective assembly in a cell with a 1D groove template as the substrate can induce a highly ordered 2D square-lattice colloidal crystal with a minimum density of defects. The long-range ordering of the prepared 2D square symmetric colloidal crystals is characterized by electron and optical microscopy, laser diffraction, and light transmission. Transmission spectra of the prepared square symmetric colloidal crystal are measured at normal and off-normal incidence under different polarizations and are shown to be in good agreement with theoretical calculations.

Composite materials with ordered microstructures often lead to enhanced functionalities that a single material can hardly achieve. Many biomaterials with unusual microstructures can be found in nature; among them, many possess anisotropic and even directional physical and chemical properties. With inspiration from nature, artificial composite materials can be rationally designed to achieve this anisotropic behavior with desired properties. Here, a metallic wood with metal continuously filling the wood vessels is developed, which demonstrates excellent anisotropic electrical, thermal, and mechanical properties. The well-aligned metal rods are confined and separated by the wood vessels, which deliver directional electron transport parallel to the alignment direction. Thus, the novel metallic wood composite boasts an extraordinary anisotropic electrical conductivity (σ|| /σ⊥ ) in the order of 1011 , and anisotropic thermal conductivity (κ|| /κ⊥ ) of 18. These values exceed the highest reported values in existing anisotropic composite materials. The anisotropic functionality of the metallic wood enables it to be used for thermal management applications, such as thermal insulation and thermal dissipation. The highly anisotropic metallic wood serves as an example for further anisotropic materials design; other composite materials with different biotemplates/hosts and fillers can achieve even higher anisotropic ratios, allowing them to be implemented in a variety of applications.

A highly efficient 3D wood-derived carbon monolith reactor with a low tortuosity is demonstrated for high-temperature reaction applications, using catalytic steam reforming of biomass tar as the model system. Outstanding catalytic activity is achieved as the reactant gases flow through this 3D natural wood-derived catalyst, where over 99% toluene conversion and good stability at 700 °C are observed.