Copper (Cu) heat exchangers are often used as condensers because of their good heat transfer coefficient and excellent antibacterial property. However, the hydrophilicity of Cu makes it easy to form condensate water from humid air, and even frost or freeze when these exchangers are operated in cold area. The water or ice in heat exchanger provides apt environment to breed bacteria and contaminate the incoming air [1], [2], [3]. This requires significant research efforts on improving the aspects of both anti-icing and antibacterial performance of these condensers.

Superhydrophobic materials refer to materials with both a water contact angle (WCA) greater than 150° and a water sliding angle (WSA) less than 10° [4]. This type of material can trap a layer of air between water droplets and its surface to expand the thermodynamic barrier of icing [5], [6], [7]. Consequently, superhydrophobic surfaces play a key role in preventing the ice nucleation and delaying the freezing of the droplet, thus it exhibits a good anti-icing/frost performance [8], [9], [10]. Till date, many techniques such as hydrothermal synthesis [11], [12], [13], laser ablation [14], [15], [16], [17], electrochemical deposition [18], [19], [20], anodic oxidation [21], [22], [23], and other methods have been used to fabricate superhydrophobic surfaces with a certain degree of icing retardation [24]. In particular, some superhydrophobic surfaces with micro/nano-hierarchical structures presented a strong anti-icing ability [11], [25], [26].

Although the superhydrophobic surface can resist the adhesion of most bacteria [27], studies have shown that the superhydrophobic surface is more likely to breed bacteria than the smooth surface when the bacteria is too small or the surface hydrophobicity decreases [28], [29]. Thus, it is speculated that the preparation of a superhydrophobic surface using antibacterial materials can significantly improve the antibacterial performance of the superhydrophobic surface [30]. Cu ions can not only interact with the cell wall to inhibit or destroy the membrane structure of the cell [31], [32], but also enter the bacterial cell to reduce the protein or enzyme activity, and thus it can ultimately denature protein and destroy DNA molecule [33], [34]. Importantly, the superhydrophobic surface prepared with Cu or its compounds exhibits good antibacterial properties. For example, Cu deposited on the surface of the veneer [35] and zirconium [36] exhibits superhydrophobic properties and the significant reduction in in vitro bacterial adhesion activity.

However, Cu nanoparticles (NPs) are unstable in open air, as a result, they are rarely used in practical applications. As a visible-light-sensitive p-type semiconductor material [37], copper oxide can produce free radicals with a sterilization ability when exposed to sunlight, thus actually it shows better antibacterial properties than Cu [38], [39], [40], [41]. For instance, Subhadarshini et al. [42]used electrochemical deposition method to prepare Cu2O nanopetals on Cu foil, and this surface showed excellent superhydrophobic property and better antibacterial property than raw Cu foil. Mahmoodi et al. [43] used a thermal oxidation method to produce CuO nanowires (NWs) in situ on a Cu foil, which exhibited better antibacterial activity than untreated Cu foil.

Laser ablation technique offers the advantages such as high efficiency and low pollution, and it is suitable for large-scale manufacturing. Laser ablation can produce surface texture on Cu substrate and then convert the surface into a superhydrophobic state by surface modification [44], [45]. In this study, aiming at improving the antibacterial and anti-icing performance of Cu, an ultraviolet (UV) laser was used to construct a rough surface microstructure and simultaneously deposit nano copper oxides on the surface to prepare micro-Cu/nano-oxides hierarchical surface structure. Chemical modification was used to reduce the solid surface tension and prepare a superhydrophobic surface. This study provides new insight into laser ablation of metals for the anti-icing as well as antibacterial application.