Regular ArticleClay-based superamphiphobic coatings with low sliding angles for viscous liquids
Graphical abstract
Introduction
Superhydrophobic surfaces have high water contact angle (CA > 150°) and low sliding angle (SA), but can be easily wetted by liquids with low surface tension [1], [2]. Differently, superamphiphobic surfaces feature high CAs and low SAs for both water and organic liquids with low surface tension [3], [4], [5], [6], [7]. Thus, superamphiphobic surfaces have very wide potential applications in many fields, such as self-cleaning surfaces, anti-oil climbing, anti-oil contamination, chemical shielding and anti-icing, etc. [8], [9], [10], [11], [12]. It has been well demonstrated that the combination of hierarchical microstructures and materials with low surface energy is a successful way to prepare superhydrophobic surfaces [13], [14], [15]. However, it is not that easy to fabricate superamphiphobic surfaces, because the surface tension of organic liquids is much lower than that of water [7]. In spite of high CAs, most of the reported superamphiphobic surfaces do not have low SAs for liquids with low surface tension, i.e., the liquids adhere stably on the surfaces even when the surfaces were turned upside down and thus the surfaces do not have the unique self-cleaning properties [4], [16], [17], [18], [19]. Although some of the superamphiphobic surfaces achieved low SAs for the liquids with low surface tension [4], the methods are complicated and expensive in order to design sophisticated re-entrant or double re-entrant microstructures. These bottle necks seriously hindered superamphiphobic surfaces from practical applications. Up to now, preparation of superamphiphobic surfaces with low SAs for diverse liquids with low surface tension via simple methods remains challenging [14], [20].
On the other hand, the wettability of a solid surface is closely related to properties of the liquids, mainly the surface tension. The solid-liquid dynamic interaction is also highly dependent on the viscosity and density of liquids [21], [22], [23]. In the field of bioinspired superhydrophobic and superamphiphobic surfaces, we simply used pure liquids like water and n-hexadecane as the probes to study their wettability [24], [25], [26]. This is important but insufficient to demonstrate the wettability of super anti-wetting surfaces, as liquids of diverse compositions, e.g., solutions, suspensions and emulsions, are used in academic research, industrial production and our daily life. For example, viscous liquids like polymer solutions and suspensions with high solid contents are frequently encountered, whereas their interaction with super anti-wetting surfaces is yet to be studied. A drop’s impact, motion, and rebound on a superamphiphobic surface rely on wettability of the superamphiphobic surface, impact velocity and inherent properties of the liquid drop. Compared to the liquids with high surface tension and low viscosity, it is challenging to prepare superamphiphobic surfaces with excellent static and dynamic repellency to the liquids with low surface tension and high viscosity. Until now, we can only found limited examples about the interaction between super anti-wetting surfaces and liquids with relatively high viscosity including super-cooled water (2.66 mPa·s at −10 °C) [22], [27], water/glycerol mixture (0.89–150 mPa·s) [23] and shampoo [28]. For example, Chen and Bonaccurso studied the effects of surface wettability and liquid viscosity on the dynamic wetting of individual drops by using water/glycerol mixtures that have comparable surface tensions (62.3–72.8 mN m−1) but different viscosities (1.0–60.1 mPa·s) [29]. Bhushan and his colleague fabricated superamphiphobic surfaces with repellency to shampoos [28].
Here, we report fabrication of superamphiphobic coatings with low SAs for the liquids with extremely high viscosity and low surface tension by the combination of organosilanes and attapulgite (APT). APT is a kind of phyllosilicate clay with a unique nanofibrous or nanorod-like microstructure [30].
Section snippets
Materials
Tetraethoxysilane (TEOS, 99.9%) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES, 97.0%) were purchased from Sigma-Aldrich. APT was supplied by Jiuchuan Technology Co. Ltd., Jiangsu, China. Ammonia (25.0–28.0 wt%), anhydrous ethanol (>99.7%), glycerol (98.0%), and n-hexadecane (>99.0%) were purchased from China National Medicines Co. Ltd. Hydroxyl-terminated polybutadiene (HTPB, >99.8%) was purchased from China Haohua Chemical Group Co., Ltd, with an average molecular weight of 3000. Al
Preparation of APT@F-POS superamphiphobic coatings
The preparation of the APT@F-POS superamphiphobic coatings is schematically shown in Fig. 1a. First, the APT@F-POS suspensions were prepared by ammonia-catalyzed hydrolytic condensation of TEOS and PFDTES in the presence of APT in ethanol. The APT nanorods are ∼1 μm in length and ∼50 nm in diameter (Fig. 1b) [31]. After hydrolytic condensation of the silanes, film-like F-POS was generated on the surface of the APT nanorods and among the nanorods (Fig. 1c). Subsequently, the superamphiphobic
Conclusion
In summary, superamphiphobic coatings with high repellency to various liquids including water, n-hexadecane, viscous HTPB and HTPB/Al are prepared by the combination of natural nanoclay and organosilanes. The introduction of the nanoclay generated a two-tier hierarchical micro-/nanostructure of the coatings. The superamphiphobicity and solid-liquid adhesion forces rely on microstructure of the coatings, which can be easily regulated by the nanoclay content. The superamphiphobicity reached the
Acknowledgements
This work was supported by the Presidential Foundation of China Academy of Engineering Physics (YZ2015010), National Natural Science Foundation of China (51873220 and 51503212), Funds for Creative Research Groups of Gansu, China (17JR5RA306), Major Projects of the Natural Science Foundation of Gansu, China (18JR4RA001) and the Talents of Innovation and Entrepreneurship Project of Lanzhou, China (2016-RC-77).
References (37)
- et al.
Adhesion and friction properties of micro/nano-engineered superhydrophobic/hydrophobic surfaces
Thin Solid Films
(2010) - et al.
Temperature-dependent bouncing of super-cooled water on teflon-coated superhydrophobic tungsten nanorods
Appl. Surf. Sci.
(2013) - et al.
Learning from ancient maya: preparation of stable palygorskite/methylene blue@SiO2 Maya blue-like pigment
Micropor. Mesopor. Mater.
(2015) - et al.
Polyester materials with superwetting silicone nanofilaments for oil/water separation and selective oil absorption
Adv. Funct. Mater.
(2011) - et al.
Oil/water separation with selective superantiwetting/superwetting surface materials
Angew. Chem. Int. Ed.
(2015) - et al.
Designing superoleophobic surfaces
Science
(2007) - et al.
Candle soot as a template for a transparent robust superamphiphobic coating
Science
(2012) - et al.
Super oil-repellent surfaces
Angew. Chem. Int. Ed.
(1997) - et al.
Superoleophobic coatings with ultralow sliding angles based on silicone nanofilaments
Angew. Chem. Int. Ed.
(2011) - et al.
Superomniphobic surfaces for effective chemical shielding
J. Am. Chem. Soc.
(2013)
Flexible superamphiphobic film for water energy harvesting
Adv. Mater. Technol.
A superamphiphobic coating with an ammonia-triggered transition to superhydrophilic and superoleophobic for oil-water separation
Angew. Chem. Int. Ed.
Single-droplet multiplex bioassay on a robust and stretchable extreme wetting substrate through vacuum-based droplet manipulation
ACS Nano
Solvent-free synthesis of microparticles on superamphiphobic surfaces
Angew. Chem. Int. Ed.
Repellent surfaces. Turning a surface superrepellent even to completely wetting liquids
Science
Coatings super-repellent to ultralow surface tension liquids
Nat. Mater.
Ultrafast processing of hierarchical nanotexture for a transparent superamphiphobic coating with extremely low roll-off angle and high impalement pressure
Adv. Mater.
Superoleophobic surfaces
Chem. Soc. Rev.
Cited by (0)
- 1
These authors contributed equally to this work.