The superhydrophobic phenomenon exemplified by the lotus leaf serves as an archetypal model in surface science [1]. The structure of the lotus leaf consists of a combination of two scales of roughness: around 10 μm and a fine structure around 100 nm, known as a layered micro- and nanostructure [2]. Contributing to the leaf's hydrophobicity are epidermal wax crystals, which range in height from 1 to 5 μm and overlay the surface [1,3]. Intriguingly, despite the wax having a water contact angle (WCA) of just 110°, it does not exhibit a significant degree of hydrophobicity [[2], [3], [4]]. Hence, it is conjectured that the superhydrophobic properties are mainly due to the combination of the layered micro- and nanostructures with the waxes [2,4,5]. To attain superhydrophobic characteristics, researchers have employed bionanotechnology to engineer low surface energy and micro/nanoscale architectures onto various substrates such as glass, textiles, and wood-based composites (WBCs). This engineering results in a WCA exceeding 150° and a sliding angle (SA) below 10° [6]. Numerous methods have been developed for the fabrication of superhydrophobic coatings with excellent surface properties, including, but not limited to, the dip-coating, etching, electrostatic spinning, layer-by-layer assembly, vapor deposition, and hydrothermal methods. These methods have a wide range of applications in self-cleaning [7], anti-fouling [8], resistance reduction [9], anti-icing [10], oil-water separation [11], energy saving [12], and more. In the context of climate change mitigation and the imperative of achieving net-zero carbon dioxide emissions, the significance of biomass materials is further amplified [13].

Biomass materials are receiving unprecedented attention. As one of the most prevalent renewable biomass resources globally [14], WBCs serve a dual role in both effective carbon emissions mitigation and extensive utility in various sectors, such as construction, interior decor, flooring, furniture fabrication, and tool manufacturing [15]. The primary constituents of wood are three polymeric compounds: cellulose, hemicellulose, and lignin [16]. Notably, cellulose and hemicellulose have structural compositions rich in free hydroxyl groups (-OH), which render them highly hygroscopic [17]. Under specific thermal and humidity conditions, the free hydroxyl groups can adsorb water molecules from the air through hydrogen bonds and intermolecular forces. This moisture uptake exacerbates fiber degradation, which manifests as swelling, cracking, deterioration of mechanical properties, and increased susceptibility to fungal decay [18]. Concurrently, wood exhibits strong adsorption and capillary condensation phenomena due to its structure, which contains a large number of capillaries and micro hair cells, characterized by high porosity and a vast internal surface area. In humid air, capillary condensation occurs as the wood absorbs water vapor, reaching the fiber saturation point [19]. WBCs have received extensive research and attention due to their functional diversity, and advanced functional structures are made based on the microstructure of wood. Collectively, these factors adversely affect the dimensional stability of WBCs, significantly compromising their mechanical integrity and, consequently, their lifespan and application range [20,21]. As such, enhancing the dimensional stability of WBCs and imparting a certain degree of hydrophobicity to WBCs has become a hot research topic in recent years.

In this review, we succinctly elucidate three foundational models governing superhydrophobic structures: the Young's model, the Wenzel model, and the Cassie-Baxter model. We then discuss the microstructures of superhydrophobic coatings from a theoretical modeling perspective and present equations for calculating surface energy. Subsequently, we examine the pivotal factors influencing superhydrophobic properties, focusing on preparation methodologies, the selection of chemical reagents, and the choice of wood species. This comprehensive review outlines the development of SWBCs preparation methods over the past few years, including their benefits and drawbacks. We further detail the chemical constituents employed and investigate how different wood species inherently affect SWBCs. The fundamental characteristics of SWBCs developed to date and their limitations for various application scenarios are methodically detailed (Fig. 1). In the concluding section, we highlight the prevailing challenges in optimizing SWBCs' performance and propose potential future solutions based on cutting-edge research findings.