## 1 Introduction
Therefore, the development of facile and \"green\" technologies that can change the polarity of HNTs, as well as enhance the durability is of great importance and urgently needed. Fortunately, the strong adhesive mechanism of marine mussels was deciphered by [PERSON] and his partners, finding that the catecholic amino acid, 3,4-dihydroxyphenyl-1-alanine (DOPA), was the primary functional molecular of mussel adhesive proteins (MAPs), which permitted this marine animal to firmly adhere to the surfaces of various substrates [28]. Inspired by MAPs, an easily accessible small molecule, \(\alpha\)-(3,4-Dihydroxyphenyl)-\(\beta\)-aminoethane (dopamine), has been widely used to achieve multifunctional surfaces via oxidative self-polymerization in a mildly alkali solution (pH = 8.5) that is similar to the marine environment without adding extra toxic reagents [29]. This anchored polydopamine (PDA) layer that contains a large number of free catechol groups can serve as an \"activated platform\" for large-scale multiplicities of secondary reactions including reducing metal ions to form metallic nano-coatings and grafting with amino groups through Michael addition or Schiff base reactions [30]. In addition, the small dopamine molecule can easily enter into the inner space of HNTs, forming PDA functional layer both on the internal and external surfaces of HNTs [31]. Therefore, it is believable that this mussel-inspired method will definitely create the biomimetic micro/nano hierarchical structures on HNTs surfaces with robust superhydrophobic abilities. In this study, we developed a convenient approach of transforming water-swellable halloysite into superhydrophobicity with tremendous durability. Although some researchers have focused on the use of dopamine to create catechol functional coatings on the surfaces of HNTs [31; 32; 33], to the best of our knowledge, it has been no previous reports on using mussel-inspired catecholic layers to graft long chain alkylamines (octadecylamine) for the preparation of superhydrophobic HNTssurfaces. In this process, dopamine can be immobilized to Al and Si atoms via non-covalent or covalent bonds, and be spontaneously physically polymerized into PDA, forming the \"activated platform\" to tightly adhere to the HNTs surfaces for forthcoming secondary reactions. Then, the anti-water octadecylamine (ODA) was linked to the PDA layer through Michael addition or Schiff base reactions, thus the hydrophobic surfaces were successfully established. Furthermore, Vitamin M (VM) was added into the reaction system acting as catalyst to require the ultimate superhydrophobic HNTs by hindering the formation of smooth PDA layers and improving the roughness of the PDA and ODA co-modified surfaces. The mussel-inspired surface modification method exhibits the following novelty merits and dramatic benefits. (1) The procedure of coating PDA onto HNTs were mild, simple, and highly efficient, which can be realized only through immersing HNTs in a weak alkaline dopamine solution at room temperature without intricate instruments; (2) The only solvents on this approach were water and ethanol, which was not toxic, sustainable, and friendly to environment; (3) Both the internal and external surfaces of HNTs were modified without damaging the original nanotube structures; and, (4) The resultant superhydrophobic HNTs surfaces exhibit a robust stability in diverse severe conditions, including boiling water, strong acid solution, organic solvent, high intensity sunlight, and ultrasonic cleaning, which made HNTs have outstanding potential as adsorption substrates for various applications such as thermal energy storage and wastewater treatment.