Conformally anodizing hierarchical structure in a deformed tube towards energy-saving liquid transportation

The creation of drag-reducing surfaces in deformed tubes is vital importance to thermal management, energy, and environmental applications. However, it remains a great challenge tailor the surface structure wettability inside slim complicated feature. Here, we describe an electrochemical anodization strategy achieve uniform superhydrophobic coating TiO2 nanotube arrays throughout inner deformed/bend titanium tubes. Guided by hybrid carbon fibre cathode, conformal electric field can be generated adaptatively fit complex geometries tube, where structural design with rigid insulating beads self-stabilize cathode at coaxial position tube electrolyte flow. As result, obtain water contact angle 157° hysteresis less than 10°. Substantial drag reduction realised overall up 25.8 % for anodized U-shaped tube. Furthermore, demonstrate spatially coat geometries, energy-saving liquid transportation. This facile has implications transport processes user-friendly approach engineer regardless deformation tube/pipe.