## 1 Introduction  
In nature, bacteria attach to surfaces and interfaces in the form of microbial communities, and embed in a matrix of hydrated extracellular polymeric substances (EPS), referred to as a biofilm [1]. Bacteria in biofilm are up to 600 times less susceptible to disinfectants and 1000 times less vulnerable to antibiotics compared to planktonic bacteria, because the structure of the biofilm protects them from environmental insults [2; 3]. Biofilms are ubiquitous and responsible for numerous problems, either in daily life or in industry [4; 5]. Most bacterial infections and a variety of other diseases including some cancers are related to biofilms [6; 7; 8; 9]. Therefore, biofilms are an urgent problem that needs to be solved. Numerous studies have been done to solve this problem; among them, developing antibacterial materials has proved one of the most effective ways [10; 11; 12; 13; 14]. As recently reported, current antibacterial materials can be classified into two categories: surfaces that resist bacterial attachment and surfaces that kill the bacteria. Bacteria-resistant surfaces normally possess certain properties that result in substrates resisting bacterial attachment, such as superhydrophobic surfaces. On the other hand, bactericidal surfaces will kill bacteria using biocides that are incorporated into the surface, e.g., antibacterial metals, peptides, and so on [15; 16]. Bacterial adhesion is influenced by the chemical reactivity of the surface, which is controlled by the surface properties, including surface composition, structure and electronic properties [17; 18]. Surface properties, such as hydrophobicity/hydrophilicity [19; 20; 21], roughness [22; 23; 24; 25] and surface free energies [26; 27] have been shown to influence bacterial adhesion. Numerous studies have investigated the correlations between bacterial adhesion and surface properties, but there are no consistent answersto date. For surface wettability, most researchers agree that bacteria tend to adhere to hydrophobic surfaces rather than hydrophilic ones [19; 28; 29; 30]; in contrast, [PERSON] et al. found that hydrophilic surfaces promote bacterial adhesion [31; 32]. Many researchers have shown that surface roughness influences bacterial adhesion, in that the extent of adhesion increases in correlation with surface roughness [24; 25; 33; 34]. However, some researchers have pointed out that surface roughness plays only a limited role in the initial adhesion; the influence of surface roughness is more important regarding biofilm detachment [35]. [PERSON] et al. found that there was little correlation between adhesion and surface roughness [22; 23; 36]. Moreover, [PERSON] et al. reported that the influence of surface roughness on biofilm formation was different with different bacteria [37]. According to the relationship between surface energy and bacterial adhesion found by [PERSON] et al., surface free energies influence bacterial adhesion significantly; bacterial adhesion was shown to be minimized when the surface free energy was around 25 mN/m [26; 38; 39]. [PERSON] et al. demonstrated that bacterial adhesion decreased as surface energy increased and vice versa [40; 41]. However, some reports showed contrary results [42; 43]. As the cell envelope of bacteria is charged, scholars propose that electrostatic interactions will also affect bacterial adhesion and the stability of biofilms [44; 45; 46]. Studies have proved that cations in solution (e.g., Ca\({}^{2+}\), Mg\({}^{2+}\)) affect biofilm formation [47; 48; 49]. Put another way, a substratum with a charged surface will also influence the formation of biofilms. Normally, the cell envelopes of bacteria are negatively charged at neutral pH; therefore, surfaces with a negative charge will probably inhibit biofilm adhesion because of electrostatic interactions [44; 50; 51]. The surface topography is also an important factor in relation to bacterial adhesion.