Influence of the hydrophilic structural parameters of titanium alloy bioinspired Nepenthes on droplet flow characteristics

Abstract

A bioinspired Nepenthes-inspired hydrophilic track was prepared on a Ti4Al6V substrate, and droplet flow behavior was explored under different texture widths (B), texture orientation angles (α), and texture spacings (L).Simulation indicated that the droplet migration distance decreased with increasing B. The optimal droplet migration performance was achieved at B^* = \(\:\frac{\text{B}}{\text{W}}\) = 0.1, α = 45°, and L^* = \(\:\frac{\text{L}}{\text{W}}\) = 0.5, with a migration distance of 14.85 mm, The migration efficiency η = 99%. At B* = 0.1, L* = 1, α = 45°, the migration distance is 13.35 mm, η = 89%, which was 4.6% larger than at B* = 0.1, L* = 1,α = 90°. When B and α were fixed, the migration distance decreased with increasing L. Specifically, at B* = 0.1 and α = 45° and L* = 0.5, the migration distance was 33.8% longer than that at L* = 2. Experimental results on the flow of droplets along the hydrophilic track demonstrated the migration efficiency under parameters of: η = 76% at α = 30°, L* = 1.0, B* = 0.4, η = 86% at α = 45°, L* = 1.0, B* = 0.1, and η = 94% at α = 45°, L* = 0.5, B* = 0.1. Mechanistically, increasing L reduced hydrophilic unit density, weakened the capillary force gradient, and thus shortened migration distance. Texture width B regulated the balance between capillary and viscous forces, while orientation angle α modified the capillary force vector and its components, collectively governing the droplet flow behavior.