In the quest for innovative materials with enhanced functionalities, the development of superhydrophilic surfaces has garnered significant attention. These surfaces, characterized by their ability to attract water, have a wide range of applications, from self-cleaning windows to antifogging coatings on lenses. Several different approaches have been taken to fabricate superhydrophilic surfaces. Both suitable surface chemistry and surface roughness are needed. Characterization of such surfaces is commonly done with contact angle measurements.
What is Contact Angle?
The contact angle measures the wettability of a surface, which is defined as the angle formed between a liquid droplet and the surface it rests upon. A lower contact angle indicates a more hydrophilic (water-attracting) surface, while a higher angle suggests hydrophobicity (water-repelling). In the context of superhydrophilic surfaces, a contact angle of less than 10° is often desired.
Fabrication of Superhydrophilic Surfaces
There are several possible approaches to fabricate superhydrophilic surfaces. In principle, to achieve superhydrophilicity both suitable surface chemistry as well as surface roughness is required. In the article written by Kaya and Cengiz, authors utilized a one-step, one-pot sol-gel method to create a composite surface composed of poly(hydroxyethyl methacrylate) (P(HEMA)) and tetraethoxysilane (TEOS), with varying silica content. This method allows for the simultaneous polymerization and sol-gel reaction, resulting in a uniform distribution of silica nanoparticles within the polymer matrix.
Correlation Between Contact Angle and Antifogging Properties
The research highlights a direct correlation between the contact angle and the antifogging performance of the surfaces. Surfaces with a contact angle below 15° exhibited excellent antifogging properties, as the low angle facilitates rapid water spreading and evaporation, preventing fog formation. Conversely, surfaces with a contact angle above 25° lost their antifogging capabilities.
The study found that increasing the silica content in the composite reduced the contact angle, enhancing the surface's hydrophilicity. For instance, a surface with 30% silica content achieved a contact angle of less than 4°, demonstrating superior antifogging performance.
Practical Implications
These findings have significant implications for industries requiring clear visibility and cleanliness, such as automotive, optical, and solar panel sectors. By optimizing the silica content and ensuring a low contact angle, manufacturers can produce surfaces that remain clear and fog-free under various environmental conditions.
In conclusion, the study underscores the importance of contact angle measurements in the design and application of superhydrophilic surfaces. By understanding and manipulating this parameter, it is possible to enhance the antifogging properties of materials, paving the way for more efficient and practical applications in everyday life.
