applied in many fields such as information, energy, and security technologies. [4][5][6] It should be noted that we do not particularly introduce the research progress of metamaterials due to the limited length of the Essay, and readers can find many review articles in the literature. [7][8][9][10] Currently, most researches focus on the relationship between compositions/crystal structure and properties, but the effect of functional units/ordered structure on material properties has received relatively little consideration. If larger functional units instead of a single atom or molecule can be arranged and assembled in a certain order, this will lead to abnormal (exceptional) physical properties. There have been some reports on pursuing novel properties by designing and assembling functional units, which can be either artificial microstructures, or simply the natural domains, phases, twins, components or heterostructures of materials. Here, we will summarize these works and propose a "paradigm" of material research through designing and constructing ordered structures with functional units (OSFU). We hope to draw the attention of researchers to this OSFU concept, and promote the development of this strategy toward deeper understandings and broader applications.
OSFU-Related Exploration for Improved Properties
Optical PropertiesStructural colors are frequently found in animals or plants, which originate from light interfering with their sub-micrometer photonic structure features. The well-known examples include peacock feather, butterfly wing, and opal crystal. Researchers from MIT found the colored stripe of the bluerayed limpet results from the light interference with the photonic architecture embedded limpet shell. [11] The OSFUscalcite lamellae in this case are stacked in a co-orientated manner forming periodically layered zig-zag architecture. The photonic multilayer system serves as an optical interference filter to produce the strong blue reflection. Scientists at University of Geneva studied the active color change in chameleons (Figure 1). [12] It was demonstrated that there are two layers of dermal iridophores with functional units of guanine nanocrystals arranged in a triangular lattice underneath the epidermis, and the arrangement of these OSFUs is responsible for the color change. When a chameleon is relaxed, the functional guanine nanocrystals are closely spaced with a small Realizing new functions through the construction of ordered structures not only exists naturally in nature, but also in artificial materials. However, much research focuses more on the relationship between structure and performance rather than on the impact of functional units themselves. Reviewing previous research findings, a "paradigm" of material research is proposed, which is based on ordered structures with functional units (OSFU) such as compositions, phases, domains, and twins. The goal is to draw more intensive attention of researchers to this concept and thus to promote the development of this field toward a deeper and ...