During water droplet impingement onto a rice-leaf-inspired grooved superhydrophobic surface, the unidirectional textures can reduce the solid–liquid contact time through modifying the droplet impact dynamics. The influence of the groove geometry on the splashing of impacting droplets is still unrevealed. In this study, we experimentally identify the droplet bouncing and splashing regimes on grooved superhydrophobic surfaces of varying parameters. Asymmetric spreading and retracting of droplets are observed on the surfaces, accompanied by obvious liquid jets generated within the grooves. As the impact velocity increases, secondary droplets are ejected from the rim of the liquid jets, which is the onset of droplet splashing on the grooved superhydrophobic surfaces. We find that the critical Weber number for the splash of liquid jets decreases with the groove width but increases with the droplet diameter. Scaling analysis is performed to model the splashing criteria and explain its dependence on groove parameters and droplet properties. This research advances the understanding of droplet splashing dynamics on textured superhydrophobic surfaces, which is promising for some agricultural and industrial applications.

Functional wetting surfaces have excellent prospects in applications including self-cleaning, anti-fog, anti-icing, corrosion resistance, droplet control, and friction power generation. Laser micromachining technology is an advanced method for preparing such functional surfaces with high efficiency and quality. To fully exploit the potential of laser micromachining and the related hybrid methods, a wide spectrum of knowledge is needed. The present review systematically discusses the process capabilities and research developments of laser micromachining and its hybrid methods considering the research both in basic and practical fields. This paper outlines the relevant literature, summarizes the characteristics of functional wetting surfaces and also the basic scientific requirements for laser micromachining technology. Finally, the challenges and potential applications of superhydrophobic and superoleophobic surface are briefly discussed. This review fills the gap in the research literature by presenting an extended literature source with a wide coverage of recent developments.

Regulating the impact dynamics of water droplets on a solid surface is of great significance for some practical applications. In this study, the droplet impingement on a flexible superhydrophobic surface arrayed with micro-scale grooves was investigated experimentally. The surface was curved into cylindrical shapes with certain curvatures from two orthogonal directions, where axial and circumferential grooves were formed, respectively. The effects of curvature diameter and Weber number, as well as the orientation of grooves on droplet spreading and retracting dynamics were analyzed and explained. Results show that the circumferential grooves promote the spreading of a droplet in the azimuthal direction, where the droplet rebounds from the surface with a stretched shape. This mechanism further reduces the contact time of impacting droplets on the superhydrophobic surface compared to the other curving mode.

The interaction between ink drops and permeable textiles is complicated but crucial for textile inkjet printing. To address this, a modified model was developed in the current research by employing the volume of fluid method. The capillary force and the flow resistance were taken into account in the momentum equation, enabling the simulation of both spreading and penetration of ink drops upon impacting a textile. The evolutions of drop morphology, pressure distribution, and velocity field were investigated. An interesting finding is the entrapment of air bubbles with higher internal pressure at the intersection of warp and weft yarns due to the flow difference in the axial and radial directions of a yarn. To explore the influence of critical factors, parametric study was further conducted by varying impact velocity, drop diameter, and ink viscosity. Results show that increasing impact velocity enhances both the spreading and penetration of ink drops. The increase in drop diameter leads to a larger maximum spreading ratio but a smaller penetration ratio, as the penetration dynamics in the numerical model is independent of drop size. Additionally, ink drops with a higher viscosity display reduced spreading and penetration within the textile, primarily due to the rise in flow resistance and energy dissipation.