ANISOTROPIC WETTING BEHAVIORS OF DROPLETS ON THE SURFACE OF ASYMMETRICAL MICROGROOVES

The wetting behaviors of droplets on anisotropic surface have importantly scientific research and engineering value for the control of droplet operation and movement. In the paper, a gravity test system is used to characterize the anisotropic wetting behaviors of droplets on the surface of asymmetric grooves, and the effects of groove geometry asymmetry, groove height and width, and oil immersion treatment on droplet static and dynamic wetting behaviors are studied.The results indicate that geometric asymmetry of the groove affects the wetting state of the droplet, and the difference of the contact angle of the droplet in different directions on the surface of the asymmetric groove is greater than that in the symmetrical groove, so the anisotropy of the asymmetric groove surface is more significant than that of the symmetric groove surface. The contact angle of droplets on grooves surface with oil immersion treatment decreases, resulting in more significant anisotropy than that in the non-oil immersion state. The contact angle of the asymmetric groove surface decreases with the increase of the groove height h, and increases with the increase of the width c. The regulation effect of height and width on the asymmetric surface after oil immersion is basically ineffective with the same contact angle anisotropy characteristics in different specimens basically due to the difference of contact angle among specimens reduced by surface oil immersion treatment. When the width of the groove increases, the sliding angle of the surface of the asymmetric grooves decreases. At the same time, the sliding angle of the droplet moving along the direction of the asymmetric groove from the large top angle to the small top angle is larger than that in the opposite direction, and the larger the droplet volume, the smaller the sliding angle. Finally, the above laws are analyzed by contact line theory, and the slip angle theory formula is derived from the surface energy model, which is basically consistent with the experimental results.