Directional transport of liquid droplets is crucial for various applications including water harvesting, anti-icing, and condensation heat transfer. Here, bouncing of water droplets with patterned superhydrophobic surfaces composed of circular equidistant grooves was studied. The directional transport of droplets toward the pole of the grooves was observed. The impact of the Weber number, initial polar distance r, and geometrical parameters of the surface on the directional droplet bouncing was experimentally explored. The nature of bouncing was switched when the Weber numbers exceeded We ≅ 20−25. The rebouncing height was slightly dependent on the initial polar coordinate of the impact point for a fixed We, whereas it grew for We > 20. The weak dependence of the droplet spreading time on the Weber number was close to the dependence predicted by the Hertz bouncing, thus evidencing the negligible influence of viscosity in the process. Change in the scaling exponent describing the dependence of the normalized spreading time on the Weber number was registered for We ≅ 25. The universal dependence of the offset distance ΔL of the droplets on the Weber number ΔL/D 0 ∼ We 1.5 was established. The normalized offset distance decreased with the normalized initial polar distance as ΔL/D 0 ∼ (r/S) −1 , where D 0 and S are the droplet diameter and groove width, respectively. This research may yield more insights into droplet bouncing on patterned surfaces and offer more options in directed droplet transportation.

In the first part of this research, we reported the experimental study of the drop impact on the superhydrophobic circular groove arrays, which resulted in a directional droplet transport. In the second part, we further explored the influence of the Weber number (We), ridge height (H), and the deviation distance (r) between the impacting point and the center of curvature on the lateral offset distance (ΔL) of bouncing drops. The suggested theoretical analysis is in reasonable agreement with the experimental observations. We demonstrate that a Cassie–Wenzel wetting transition occurred within the microstructures of the relief under the threshold Weber number, for example, We ≅ 19–25, which switched the nature of drop bouncing. The dynamic pressure plays a decisive role in the directional droplet transport. The reported investigation may shed light on the solid–liquid interactions occurring on the patterned hierarchical surfaces and open up new opportunities for directional droplet transportation.

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Phenols pose a great threat to human and environment due to their high toxicity and low bio‐degradability. Therefore, the development of a rapid and sensitive detection method for multiple phenols is of great importance. Here, a colorimetric detection method based on Fe3O4/SnS2 composites was established for the detection and discrimination of ten phenols for the first time. The results demonstrated that the incorporation of the photo catalyst SnS2 significantly improved the peroxidase‐like activity of Fe3O4, leading to an enhancing efficiency of the colorimetric detection method. The developed method was capable of detecting phenol within a concentration range of 0.5–2000 μM, with detection limit as low as 0.06 μM. This method was successfully applied to detect total phenols in samples obtained from two sewage treatment plants and seawater. Furthermore, by employing principal component analysis, the established colorimetric method enabled the simultaneous discrimination of all ten phenols. The performance was further evaluated by accurately identifying binary or ternary mixtures of phenols, and even identifying the type of phenol in 10 unknown samples containing one of the ten phenols. These findings highlight the potential of the Fe3O4/SnS2 composite as a promising candidate for the simultaneous detection of multiple phenols in liquid samples.