Towards the scaling of all-organic hydrophobic and slippery liquid-infused substrates

Significance 

The popularity and increased applications of high liquid repellant surfaces can be attributed to their unique antibacterial, antifouling, anticorrosion and anti-icing properties as well their environmental benefits and energy savings due to reduced friction and residues. However, large-scale production of such surfaces for various applications has remained a significant challenge due to a lack of simple, cost-effective and scalable production methods. Moreover, the existing production strategies are either based on non-scalable techniques or involve several fabrications steps that further complicate producing hydrophobic surfaces. Therefore, large-scale production of special surfaces is critical in expanding their applications, and it demands the development of more effective production methods.

Textured and slippery lubricated surfaces are the two main surfaces with special wettability properties. Interestingly, they are both inspired by nature and require either hydrophobic and textured substrates. The textured surfaces can be realized by either generating porosity or roughness on low-surface energy substrates or chemically modifying the textured structures with low-surface-energy compounds. However, these approaches require additional fabrication steps making the production methods more cumbersome and complicated. Lately, research has concentrated on scaling and simplifying the existing methods while enhancing the properties of the resulting surfaces. For example, previous research on materials with excellent liquid repellency concentrated on generating liquid/lubricant infused surfaces (LIS) using superhydrophobic textured polymer layers. To produce durable and stable LIS, many surface properties such as roughness, porosity and re-entrant must be considered.

Motivated by the previous research findings, a group of researchers from the Spanish National Research Council: Elisabet Afonso, Dr. Aránzazu Martínez-Gómez, Dr. Pilar Tiemblo, Dr. Nuria García proposed a simple and scalable industrial method for production of all-polymer hydrophobic surfaces for slippery LIS. The surfaces were built on PVDF/PMMA blended films. The decision to use PVDF was partly based on its remarkable mechanical and chemical properties, its complex crystalline morphology, and its capability to form homogenous blends with different polymers. In particular, the authors explored the morphological and miscibility tuning of PVDF/PMMA blends to construct superhydrophobic surfaces, which is sparsely studied in the literature. Furthermore, the feasibility and practicability of the proposed methods were validated by demonstrating the effectiveness of the resulting surfaces in generating LIS layers with outstanding slippery properties. Their research work is currently published in the research journal, Applied Surface Science.

Results demonstrated that the methodology is simple and easy to implement as it does not require fluorination like most of the existing methods. This enabled fast and easy preparation of the rough surfaces via treatment with common solvents like ethanol, and the roughness profile could be tuned by varying the solvent immersion time. Based on the analysis of the roughness parameters, the hydrophobicity of the surface increased with more re-entrant profile. Furthermore, the surfaces were successfully infused with lubricants, specifically silicon oils, to prepare LIS. The resulting surfaces were not only homogenous and transparent but also exhibited relatively high water sliding velocities.

In summary, the study demonstrated the effective preparation of large surfaces exhibiting superhydrophobic properties desirable to generate liquid-infused surfaces with outstanding slippery properties. This method relied on the advantage of the multiphasic nature of the two conventional polymers and their associated blends as well its ability to effectively control the kinetics of the resulting morphology, which is considered a critical feature of polymers. Based on the results, the re-entrant profile was identified as a key parameter in LIS design. In a statement to Advances in Engineering, the authors noted that the scalability, simplicity, and efficiency of the proposed method makes it promising for fabricating high-performance surfaces for numerous applications. In addition, they pointed out that this work is a proof of concept of this methodology, which is being testing with other conventional polymers.

Towards the scaling of all-organic hydrophobic and slippery liquid-infused substrates - Advances in Engineering

About the author

HEMPOL research group, belonging to the Institute of Polymer Science and Technology, ICTP-CSIC (Spain), uses its polymeric materials knowledge and expertise to the development of products for varied application fields including packaging and energy storage, among others. Our distinct feature is that we try to make it by industrially appealing processes going for sustainable, effortless and scalable preparation routes. The group has been working on surfaces with controlled wettability for more than a decade, and we believe that a structured roughness profile, a must for this kind of surfaces, can be achieved by approaches not relying on composite materials and/or coatings. Both approaches may complicate recyclability and durability. The methodology presented in this work is a proof of concept that we are promisingly testing with other conventional polymeric materials.

HEMPOL has participated in several academic and industrial projects during the last five years, leading European Consortiums in two international projects with other research groups and enterprises. In that time, our works are compiled in more than 30 articles in scientific journals within the fields of polymer and material research. We are very enthusiastic and host PhD and undergraduate students to transmit them our passion for polymer Science. In addition, we love doing dissemination activities to bring teens and children closer to Science and show them how Science can change our world.

Reference

Afonso, E., Martínez-Gómez, A., Tiemblo, P., & García, N. (2021). Industrially viable method for producing all-polymer hydrophobic surfaces apt for slippery liquid-infused substratesApplied Surface Science, 535, 147728.

Go To Applied Surface Science

Check Also

Mixed-mode brittle fracture test of polymethylmethacrylate with a new specimen