Polyurethane-based bionic material simulating the Vis-NIR spectrum and thermal infrared properties of vegetation

From Nature to Technology: Exploring the Potential of Plant-Based Materials and Modified Plants in Biomimetics, Bionics, and Green Innovations

This review explores the extensive applications of plants in areas of biomimetics and bioinspiration, highlighting their role in developing sustainable solutions across various fields such as medicine, materials science, and environmental technology. Plants not only serve essential ecological functions but also provide a rich source of inspiration for innovations in green nanotechnology, biomedicine, and architecture. In the past decade, the focus has shifted towards utilizing plant-based and vegetal waste materials in creating eco-friendly and cost-effective materials with remarkable properties. These materials are employed in making advancements in drug delivery, environmental remediation, and the production of renewable energy. Specifically, the review discusses the use of (nano)bionic plants capable of detecting explosives and environmental contaminants, underscoring their potential in improving quality of life and even in lifesaving applications. The work also refers to the architectural inspirations drawn from the plant world to develop novel design concepts that are both functional and aesthetic. It elaborates on how engineered plants and vegetal waste have been transformed into value-added materials through innovative applications, especially highlighting their roles in wastewater treatment and as electronic components. Moreover, the integration of plants in the synthesis of biocompatible materials for medical applications such as tissue engineering scaffolds and artificial muscles demonstrates their versatility and capacity to replace more traditional synthetic materials, aligning with global sustainability goals. This paper provides a comprehensive overview of the current and potential uses of living plants in technological advancements, advocating for a deeper exploration of vegetal materials to address pressing environmental and technological challenges.

Synthesis of Chlorophylls-Doped Guanine Crystals with High Reflection and Depolarization for Green Camouflage Coating

Hyperspectral imaging technology can record the spatial and spectral information of the targets and significantly enhance the levels of military reconnaissance and target detection. It has scientific importance to mimic "homochromatic and homospectral" camouflage materials that have hyperspectral similarity with the green vegetation, one of the most common natural backgrounds. It is a big challenge to exquisitely simulate the spectral of green vegetation in visible and near-infrared windows because of the slight differences between the artificial green dyes and vegetation, the instability of chlorophylls, and the easy loss of hydroxide bands due to the loss of water from the camouflage materials. Herein, a novel kind of biomimetic material of green vegetation was designed through the incorporation of chlorophylls into the crystal lattices of single-crystalline anhydrous guanine microplates for the first time. The synthesized chlorophylls-doped anhydrous guanine crystals exhibit high reflectance intensity and depolarization effect, thus can be applied as biomimetic camouflage materials that mimic green vegetation with high reflectivity and low polarization in the visible and near-infrared regions. The factors influencing the formation of dye-doped organic crystals under mild conditions were thoroughly investigated and the characterizations using electron microscopies and fluorescence confocal laser scanning microscopy clearly confirm the occlusion of chlorophylls into the crystal lattices of guanine crystals. The thermal stability experiments clearly indicate that the chlorophylls-doped guanine crystals possess long-term stability at high temperature. This study provides a new strategy for the synthesis of multifunctional materials comprised of organic crystals.

A Color-Changing Biomimetic Material Closely Resembling the Spectral Characteristics of Vegetation Foliage

Multispectral/hyperspectral technologies can easily detect man-made objects in vegetation by subtle spectral differences between the object and vegetation, and powerful reconnaissance increases the demand for camouflage materials closely resembling vegetation spectra. However, previous biomimetic materials have only presented static colors that cannot change color, and camouflage in multiple bands is difficult to achieve. To address this challenge, inspiration is drawn from the color change of foliage, and a color-change model is proposed with active and static pigments embedded in a matrix medium. The color of a composite material is dominated by the colored active pigment, which conceals the color of the static pigments and the color is revealed when the active pigment fades. A color-changing biomimetic material (CCBM) is developed with a solution casting method by adopting microcapsuled thermochromic pigments and chrome titanate yellow pigments as fillers in a base film with polyvinyl alcohol and lithium chloride. A Kubelka-Munk four-flux model is constructed to optimize the component proportions of the CCBM. The material has a reversible color change, closely resembles the foliage spectrum in UV-vis-NIR ranges, and imitates the thermal behavior of natural foliage in the mid-infrared regime. These results provide a novel approach to multispectral and hyperspectral camouflage.

One-step preparation of Cr2O3-based inks with long-term dispersion stability for inkjet applications

Inkjet printing of functional materials has shown a wide range of applications in advertising, OLED display, printed electronics and other specialized utilities that require high-precision, mask-free, direct-writing deposition techniques. Nevertheless, the sedimentation risk of the refractory functional materials dispensed in inks hinders their further implementation. Herein, we present a bottom-up ink preparation strategy based on Cr₂O₃ by a one-step solvothermal method. The obtained ink remained stable under an equivalent natural sediment test for 2.5 years. The chemical composition of the solvothermal product was characterized, and the mechanism of the superior dispersion stability of Cr₂O₃ particles was analysed. These amorphous Cr₂O₃ particles were capped by ligands generated via low-temperature solvothermal reactions. Ethanol and acetylacetone covering the particle surfaces play an essential role in enhancing the solubility of Cr₂O₃ particles in the solvent forming the ultrastable colloidal ink. Moreover, this ink was successfully printed using a direct-write inkjet system JetLab®II on nylon fabrics, and the printed area of the fabrics shows a spectral correlation coefficient of 0.9043 to green leaves. Finally, we believe that the one-step bottom-up fabrication method of Cr₂O₃-based pigment inks may provide a general approach for preparing metal oxide-based pigment inks with long-term dispersion stability.