Geometry-Engineered Microgrooves Broaden the Material Scope for Spontaneous Liquid Spreading

Spontaneous and rapid long-distance liquid transport is essential for applications in microfluidics, thermal management, and fog harvesting. However, enhancing transport efficiency and broadening material compatibility remain challenging. Herein, we systematically investigate how the cross-sectional geometry in open aligned microgrooves (AMGs) influences liquid spreading dynamics. We demonstrate that the "r-shaped" grooves enable the fastest and most extended directional transport, outperforming "u-shaped" and "v-shaped" designs. By adjusting the width-to-depth ratio p, the critical contact angle (θ_crit) for spreading can be tuned, reaching 47.5° at an optimal p ≈ 1.5. This behavior arises from a balance between capillary driving forces and viscous resistance within the groove, governed by the groove's overall geometry and layered fine structure. Theoretical predictions of θ_crit align well with experimental results across different geometries and are further validated using various liquids and moderately hydrophilic commercial polymers, including polyurethane and polyimide. The raised θ_crit lowers the wettability threshold, thereby expanding the range of materials suitable for spontaneous spreading. Moreover, AMGs serve as an integrated platform for parallel solution analysis, enhancing detection efficiency in real-time monitoring. This work establishes a rational design principle for efficient, self-driven liquid transport systems, with promising potential in microfluidics, sensing, and thermal management.