Surface modification techniques have significantly enhance the capillary properties of fiber materials. This study investigates whether nanoparticles or micro–nano slits play a more critical role in improving capillary performance. SiO2 micro–nano slits induced by laser texture deposition (LTD) on copper mesh improve capillary wicking performance. By varying the laser flux, researchers control both the slit dimensions and nanoparticle density. Image analysis and results indicate that the influence of micro–nano slits on capillary performance exceeds that of nanoparticles. This finding suggests that while nanoparticles have a positive effect, the primary factor for improved water absorption capacity is the micro–nano slits created by laser deposition. Thus, LTD proves effective in enhancing the capillary performance of fiber matrices, presenting promising prospects for future research in this field.