Due to the presence of many highly chemically active particles inside plasma, plasma exhibits excellent performance in material surface treatment and functionalization. It has a wide range of applications in improving the hydrophilic/hydrophobic properties of material surfaces, surface micro nano processing, and surface treatment of biological tissues. When plasma acts on the surface of materials, different effects such as cleaning, activation, etching, grafting, polymerization, etc. are produced due to the difference in discharge gas, which affects the contact angle and surface energy of the material surface, thereby improving the surface properties of the material. This interaction does not destroy the physical properties of the material itself, and its effect only occurs at micro - and nano level depths on the surface of the material. After plasma treatment, the surface of the material has new characteristics, and its surface energy and surface micro nano structure have been improved. Plasma material surface treatment can also reduce interface defects, remove surface pollutants and impurities, and the treatment process is pollution-free. Therefore, plasma modification of material surfaces has important research value.
Glass is an inorganic non-metallic material that can usually be used as a matrix material. It is combined with other reinforcing materials through a composite process to form a glass based composite material. After the composite process, the glass based composite material can improve the toughness and strength of glass. The improved glass based composite materials have demonstrated superior performance in many scientific fields such as national defense, electronic engineering, and biomedical applications. However, the interface bonding between glass and other materials is weak, and the quality of the bonding interface depends on the wettability of the material surface. Improving the wettability of the glass surface plays a crucial role in the bonding between glass and other materials. The influence of low-temperature plasma cleaning on the wettability of glass surfaces is of great research significance in order to improve adhesive strength.

Based on the advantages of plasma in material surface treatment and functionalization, this paper applies a plasma cleaning machine to modify the glass surface, aiming to improve the wettability of the glass surface through plasma cleaning technology. By measuring the contact angle of the glass surface after plasma cleaning, the wettability of the glass surface is observed to be improved. Based on scanning electron microscopy, the microstructure of the glass surface is observed to analyze whether the microstructure of the glass surface changes after plasma acts on it.

Contact angle measurement

The variation of the contact angle of the glass surface measured by the experiment with plasma cleaning time is shown in Figure 1. It can be seen from the figure that the contact angle of the glass surface significantly decreases after low-temperature argon plasma cleaning, and the wettability of the glass surface is improved. When the glass is treated with low-temperature plasma for 1 minute, the contact angle rapidly decreases, and the wettability of the glass surface is significantly improved compared to the untreated state. Within a processing time of 1 minute, as time increases, the contact angle of the glass surface gradually decreases, indicating that the wettability of the glass surface is gradually improving. This is because when plasma acts on the surface of glass, the highly active particles inside will break the original chemical bonds on the material surface, producing active groups. These active groups react with particles in the air and form some oxygen-containing active groups on the material surface. The introduction of these hydrophilic functional groups will improve the wettability of the glass surface and enhance its hydrophilicity. After the plasma acts on the glass surface for more than 1 minute, the contact angle of the glass surface remains basically unchanged, indicating that the contact angle between the glass surface and water has basically reached saturation.

Figure 1: Variation of Contact Angle on Glass Surface with Plasma Cleaning Time

Scanning electron microscope (SEM) observation

The process of plasma treatment on material surfaces not only introduces active functional groups to increase surface energy, but also may cause etching, sputtering and other reactions on the material surface, changing the microstructure of the material surface. This change in surface microphysical structure can also improve the wettability of the material surface. Therefore, in order to analyze whether the reason for the improved wettability of the glass surface after plasma cleaning includes changes in the microstructure of the glass surface, it is necessary to observe the surface morphology of the glass surface.

The observation accuracy of scanning electron microscopy can reach the nanometer level. Due to the fact that the effect of plasma on the surface of materials is only in a very shallow area, this article uses scanning electron microscopy to observe the surface morphology changes of glass surfaces before and after plasma cleaning.

Figure 2 shows the microstructure of the glass surface before and after low-temperature plasma treatment observed using a scanning electron microscope at a scale of 10 μ m. It can be seen that after 5 minutes of low-temperature plasma cleaning, there is no significant change in the microstructure of the glass surface, and the surface morphology of the glass before and after treatment is almost the same without obvious plasma etching marks. From this, it can be concluded that the improvement of glass surface wettability by low-temperature argon plasma cleaning is mainly due to the introduction of oxygen-containing functional groups, rather than the result of changes in the microstructure of the glass surface.

Figure 2: Surface morphology of glass before and after plasma cleaning

The experimental results showed that the contact angle of the glass surface decreased and the wettability of the glass surface was significantly improved after plasma cleaning, but the microstructure of the glass surface did not change significantly. This indicates that the improvement of the wettability of the glass surface after low-temperature argon plasma cleaning is mainly due to the introduction of oxygen-containing functional groups on the glass surface, rather than the result of changes in the microstructure of the glass surface.