## Materials and Methods
### Preparation of \"Environmentally Friendly\" Copper-Plated Wood-Based Composite Materials  
The preparation of \"environmentally friendly\" copper-plated wood-based composite materials was carried out on a JGP450 multi-target magnetron sputtering equipment. The schematic diagram of magnetron sputtering copper plating is shown in Figure 2. The sputtering target was a copper target (purity of 99.99%), and the copper film on the surface of the wood was prepared by direct current (DC) sputtering. The substrate was wood veneer pretreated by ultrasound. The specific magnetron sputtering conditions and process parameters are set out in Table 1.  
Figure 1: Ultrasonic pretreatment of wood veneer.  
Figure 2: Schematic diagram of magnetron sputtering copper plating.  
Structural Characterization of \"Environmentally Friendly\" Copper-Plated Wood-Based Composite Materials  
The XRD-6100 produced by Shimadzu Corporation of Japan was used to characterize the structure of \"environmentally friendly\" nano-metal wood-based composite materials under the conditions of CuK\(\alpha\) copper target radiation (\(\lambda\) = 0.154 nm), with a radiant tube voltage of 40 kV, radiant tube current of 30 mA and scanning range of 10-80 degrees. The test analysis uses Bragg-Brentano geometry. The film sample had a fixed tilt angle of 4\({}^{\circ}\), steps of 0.02\({}^{\circ}\) and a scanning speed of 2\({}^{\circ}\) per min The crystallinity of wood was measured by the crystallinity index. It was calculated from the percentage of the whole sample constituted by the crystalline part. The change in the crystallinity of wood cellulose was calculated by the empirical method of [PERSON] et al [22; 23; 24]. As shown in Formula (1), the relative crystallinity of wood cellulose is as follows:  
\[C_{r}I\%=\frac{I_{002}-I_{am}}{I_{002}}\times 100\% \tag{1}\]  
where \(C_{r}I\%\) is the relative crystallinity, \(I_{002}\) is the maximum intensity of the (002) lattice diffraction angle (near 22\({}^{\circ}\)), and \(I_{am}\) is the diffraction intensity of the amorphous region (near 18\({}^{\circ}\)).  
Micro-Morphology and Wettability Test of \"Environmentally Friendly\" Copper-Plated Wood-Based Composite Materials  
The wettability of \"environmentally friendly\" wood-based nano-metal composite materials was tested by DSA-100S contact angle measuring instrument produced by Kruss. Using the static droplet method, the test liquid was distilled water, and the volume of droplets was 7 \(\mu\)L. Each sample was randomly selected from three different positions on the surface of the sample, a single photographing test was completed in 5 s, and the average value was taken and recorded. The change in functional groups on the surface of metallized wood was analyzed by 1 iS10 Fourier transform infrared spectroscopy (FTIR) of Thermo Fisher Scientific, Inc. The instrument was equipped with a multi-functional attenuated total reflection (ATR) sampling accessory, Deuterated triglycine sulfate detector (DTGS), and diamond crystal. The infrared scanning range was 500 to 4000 cm\({}^{-1}\), resolution was 4 cm\({}^{-1}\), 32 scans were performed for each sample, and automatic air suppression was set to deduct the influence of absorption peaks caused by carbon dioxide and water in the air. The morphology of wood veneer metallization was characterized by JSM-7500F cold field emission scanning electron microscopy (SEM), and the surface elements of the wood-based nano-metal composite materials were analyzed by Oxford X-Max refrigeration energy spectrometer (EDS). The acceleration voltage of EDS is 15 KV.