Wettability characteristics of lunar soil particles from the Chang’E-5 mission: A single-particle surface analysis

• Developed a method for measuring the contact angle of micron-scale rough single particle. • The contact angle between water and lunar soil particle was obtained experimentally for the first time. • The theoretical contact angle between the epoxy and lunar soil particle was calculated by simulation. Lunar base construction has emerged as a strategic focus for global space agencies, with extrusion-based in situ resource utilization technologies recognized as a promising approach for utilizing lunar soil. However, a critical aspect of this technology lies in understanding the wettability characteristics between lunar soil and binding agents, such as water or resin. Here, the wetting dynamics were quantitatively analyzed through a custom-developed experimental apparatus combining ultra-deep field microscopy with a precision liquid evaporator. Our results demonstrate that the contact angle between a particle and water averages 108.73° with a standard deviation of 3.60°, thus indicating hydrophobicity. This phenomenon is primarily attributed to the distinctive surface morphology of the particle, characterized by adherent structures, porous architecture, and heterogeneous mineral fragments. Numerical simulations of droplet wetting behavior confirm that the Cassie-Baxter model accurately describes the observed phenomena. Through integrated experimental and computational analysis, we determined a surface tension of 8.46 mN/m between particles and water. For resin-particle interactions, the calculated Young contact angle of 96.18° exceeds the directly computed 91.90° from Young equation. This study establishes a novel framework for characterizing contact angles on micron-scale rough particles and provides crucial empirical support for extrusion-based extraterrestrial construction.