With increasing concern for food safety, the standards for food-safe materials have become more stringent. Polyether ether ketone (PEEK) is a high-performance thermoplastic with advantages such as high mechanical strength, good stability, and low density, making it widely used in aerospace, medical, and food industries. However, traditional PEEK surfaces are inherently hydrophilic, making them prone to attracting liquids like oil or milk, which can lead to contamination risks during food processing. Modifying PEEK surfaces to be hydrophobic can help maintain their self-cleaning properties. However, the traditional preparation of these self-cleaning surfaces often involves chemical methods, such as chemical etching, electrochemical etching, or chemical vapor deposition, which introduce additional chemical reagents and may pose food safety concerns. In this study, we use femtosecond laser processing technology to create micro/nanostructures on the PEEK surface, achieving a chemically-free self-cleaning surface. This method provides high precision, non-contact processing, and high efficiency without the need for chemical reagents, making it highly suitable for applications requiring stringent food safety.

In this study, femtosecond laser technology is applied to fabricate micro/nanostructures on PEEK materials to explore their self-cleaning capabilities. Initially, the influence of laser power density on the hydrophobicity of the fabricated structures is examined. Based on these findings, the effects of laser scanning speed and scanning times on hydrophobicity are further investigated. It is observed that rapid surface scanning enhances the self-cleaning properties of the structures. In addition, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) is used to measure the carbon (C) and oxygen (O) content in the structures before and after processing to analyze its influence on self-cleaning ability. Finally, a self-cleaning capability test is conducted using water, juice, and milk to evaluate the performance of the structures.

By optimizing the laser processing parameters, the fabricated micro/nanostructures demonstrate superhydrophobicity and self-cleaning properties with respect to milk and juice. Initially, the processing of the PEEK material results in micro/nanostructures with a water contact angle of 148.2° and a minimum sliding angle of 10.3°. In addition, these structures exhibit excellent self-cleaning effects for liquids such as milk and juice, with contact angles of 145.9° for milk and 143.2° for juice [Figs. 4(a) and (b)]. After further rapid surface scanning, the hydrophobicity is enhanced, reaching a contact angle of 152.5°. The liquid-repellent effects of milk and juice also improved [Figs. 4(c) and (d)]. Moreover, after 50 cycles of milk testing, the fabricated surface maintains good self-cleaning performance (Fig. 5).

We successfully fabricate a micro/nanostructure with excellent self-cleaning capabilities on the surface of PEEK material using femtosecond laser processing. By adjusting the femtosecond laser processing parameters, such as power, scanning speed, line spacing, scanning times, and power density, the adhesion properties of the PEEK surface are optimized. The optimized surface achieves the desired hydrophobicity and self-cleaning ability for milk and juice. Testing demonstrates that the surface exhibits excellent superhydrophobicity, with a maximum contact angle of 152.5° and a minimum sliding angle of 10.3°. The results of this study are expected to provide a theoretical foundation and technical support for developing new food contact materials to enhance food safety.