Preparation process and performance study of transparent veneer treated with three metal salt-based deep eutectic solvent (MDES)

This study developed a metal salt-based deep eutectic solvent (MDES) process to fabricate transparent wood from ( Chamaecyparis obtusa (Sieb. et Zucc.) Endl. var. formosana (Hayata) Rehd. ). Lactic acid combined with zinc chloride, copper chloride, or iron chloride formed the solvent, which effectively achieved primarily through the selective modification of lignin chromophores rather than extensive delignification, with only 2.78–3.99 % lignin removal while preserving the cellulose microstructure. Subsequent epoxy vacuum impregnation created a continuous phase within the DES-treated wood template. The resulting transparent wood exhibited exceptional optical performance with 90.8 % transmittance and 46 % haze, along with remarkable mechanical properties including 470 MPa tensile strength and 7.2 % elongation at break. The material also showed significantly improved water resistance with 142 % reduction in water absorption. Furthermore, the coordination between metal ions and lignin enabled effective color tuning, producing reddish-brown, bluish-green, and yellowish-red hues with Fe 3+ , Cu 2+ , and Zn 2+ respectively. This work provides an efficient and sustainable strategy for producing transparent wood with customizable optical and aesthetic properties.