Search

Natural polymer substrates are gaining attention as substitutes for plastic substrates in electronics, aiming to combine high performance, intricate shape deformation, and environmental sustainability. Herein, natural wood veneer is converted into a transparent wood film (TWF) substrate. The combination of 3D printing and origami technique is established to create programmable wood-based origami electronics, which exhibit superior flexibility with high tensile strength (393 MPa) due to the highly aligned cellulose fibers and the formation of numerous intermolecular hydrogen bonds between them. Moreover, the flexible TWF electronics exhibit editable multiplexed configurations and maintain stable conductivity. This is attributed to the strong adhesion between the cellulose-based ink and TWF substrate by non-covalent bonds. Benefiting from its anisotropic structure, the programmability of TWF electronics is achieved through sequentially folding into predesigned shapes. This design not only promotes environmental sustainability but also introduces its customizable shapes with potential applications in sensors, microfluidics, and wearable electronics. Wood-based electronics are typically constrained in their ability to undergo complex shape deformation. Here, authors integrate transparent wood film and cellulose-based conductive ink for flexible electronic origami devices that have been demonstrated as a proof-of-concept for human motion sensors. [ABSTRACT FROM AUTHOR]

Wood wettability, the process of liquid interaction with wood surfaces, is influenced by wood surface chemistry, structure, ambient conditions, and temperature. Understanding how temperature impacts wood wettability is crucial for high-temperature manufacturing processes. In this study, the sessile drop method was employed to explore the dynamic wettability of Chinese fir wood using three different liquids (water, glycerol and polyvinyl acetate (PVAc)) across a range of temperatures (25, 40, 60 and 80 °C). By considering spreading, penetration and evaporation, we revealed that the dynamic wettability of Chinese fir was strongly dependent on temperature and the type of liquid. Temperature elevation enhances wettability, leading to reduced contact angles and increased penetration ratios. Water exhibited the highest wettability, followed by glycerol, with PVAc being the least wetting agent. Notably, after 180 s of wetting at 80 °C, the measured contact angles were 0° for water, 45° for glycerol, and 120° for PVAc. When accounting for evaporation, the penetration of water decreased from 57 % to 47 % (25 °C) and 100 % to 62 % (80 °C). The activation energies for the penetration of water and PVAc into Chinese fir exhibited variations, with values of 35.3 and 158.3 kJ/mol, respectively. These comprehensive wetting results, covering spreading, penetration and evaporation, provide valuable insights into wood–water and wood–adhesive interactions, particularly when exposed to high-temperature conditions. [ABSTRACT FROM AUTHOR]

Transparent wood (TW) is an emerging composite material made of wood and infiltrated polymer that holds great promise for use in outdoor building components and photovoltaic devices. To assess the weathering resistance of TW, we conducted artificial weathering tests on three types of TW infiltrated with different polymers: epoxy (ETW), methyl methacrylate (MTW), and polyvinylpyrrolidone (PTW). After 360 h of artificial weathering, ETW and PTW exhibited less surface roughness, color difference, and volumetric swelling compared to MTW. The equilibrium contact angle rankings were: ETW (42°) > MTW (31°) > PTW (28°). The transmittances of PTW and MTW remained above 60% after weathering, and that of ETW dropped to 40%. Chemical analysis indicated that PTW was least affected by UV-induced degradation, followed by ETW, while MTW was the most severely impacted. Our comprehensive assessment revealed that the weathering resistance of TW can vary depending on the polymer type, with ETW and PTW demonstrating superior resistance compared to MTW. These findings highlight the potential of TW as a durable and sustainable material for outdoor applications and provide valuable data for optimizing the development and utilization of TW. [ABSTRACT FROM AUTHOR]

Ultraviolet light-induced discoloration is a noticeable issue when heat-treated wood is used outdoors. In this study, titanium dioxide (TiO2) particles were electrochemically deposited on the surface of heat-treated wood via a high-voltage electrostatic field (HVEF). Natural and artificial weathering tests were carried out to evaluate the anti-weathering properties after the electrochemical deposition. During HVEF treatment, Ti particles were triggered in the form of Ti4+. Ti4+ grafted with the hydroxyl groups of hemicellulose and lignin in the form of Ti–OH, and TiO2 was produced due to the oxidizing atmosphere generated by HVEF. TiO2 and Ti–OH played roles as UV absorbers, reducing degradation and discoloration of heat-treated wood. The photodegradation of lignin was alleviated effectively during both the artificial and natural weathering. The stability of wood color was remained. After the artificial weathering, the values of L*, a* and b* of the electrochemical depositied sample were 55, 10 and 25, respectively. The leaching amount of TiO2 after artificial or natural weathering was less than 6% or 40%, respectively determined by atomic absorption spectroscopy. The results suggest the feasibility of the electrochemical deposition of TiO2 for improving the anti-weathering properties of heat-treated wood and provide an effective strategy for industrial wood modification. [ABSTRACT FROM AUTHOR]

The moisture content of wood is changed during manufacturing processes, such as drying and impregnation. Understanding the water transport in wood is helpful for optimizing the manufacturing technology and improving the durability of wood products. Herein, the one-side imbibition tests of Chinese fir and poplar were carried out via direct contact with a water-saturated sponge. Imbibition amounts and orthotropic kinetics were evaluated by X-ray densitometry, where wood exhibited non-uniform and directional behaviors for water imbibition and there were variations in behavior between Chinese fir and poplar. More water uptake and faster migration were observed for poplar, while water preferentially accumulated at the wetting front for Chinese fir. The effective imbibition height of poplar was significantly higher than Chinese fir, regardless of orientation direction. Within the growth rings, Chinese fir showed heterogeneous water uptake, and faster water migration in latewood was observed. Imbibition height in a single fiber was simulated as a function of cell wall ratio, and the influences of anatomical factors on water movement were explored. These simulation assessments were consistent with the results of the one-side imbibition tests. These findings help to explain the water transport mechanism at the mesoscale and interactions between wood and water. [ABSTRACT FROM AUTHOR]

Temperature and time dependence of orthotropic viscoelastic properties for Chinese fir wood (Cunninghamia lanceolata) were investigated in tensile mode. The storage modulus (E′) and loss modulus (E″) of the longitudinal (L), radial (R) and tangential (T) specimens with adsorbed water were determined during temperature increasing period ranging from 30°C to 103°C and at a constant temperature of 103°C for 480 min. The desorption of adsorbed water provided space for the rearrangement of hydrogen bonds (RHB) within the polymer networks and caused mechano-sorptive (MS) effect. During the temperature increasing period, the MS effect increased first and following decreased for all specimens, except for the T specimens with 7.2% moisture content. In a constant temperature process, elevated stiffness and decreased damping were observed in all orthotropic directions, which suggested that the RHB effect was prominent than the dual effects of the MS and heating. Compared to the L specimens, the multi-effects of the heating, RHB and MS exerted more influence on the R and T specimens. Meanwhile, the unstable state within wood cell walls in the R and T specimens was more pronounced than that in the L specimens. Furthermore, the transverse specimens were affected by temperature to a higher degree than that of the L specimens. [ABSTRACT FROM AUTHOR]