A surface was created with the same superhydrophobic property as the lotus leaf (lotus effect) by dipping of sandblasted porous alumina into polytetrafluoroethylene (PTFE, Teflon R : DuPont TM ) solution. The fabricated engineered lotus leaf had PTFE dual-scale structures. This fabrication process has several advantages, including low fabrication cost, simplicity and easy coverage of a large area. The sandblasted porous alumina template was fabricated by sandblasting of an aluminum sheet and anodization in oxalic acid. To obtain PTFE dual-scale structures, PTFE replication based on the dipping method was used, with a 0.3 w% PTFE solution. To remove the aluminum and alumina layers, wet etching by chromic and phosphoric acid mixed solution and liquid HgCl 2 solution was used. The fabricated surface has a superhydrophobic property whose apparent contact angle of the PTFE dual-scale structures was approximately 165 • and sliding angle is less than 2 • .

Superhydrophobic nano-wire entanglement structures (NWES) were fabricated by the dipping method, based on an anodization process in oxalic acid. The pore diameter and the depth were influenced by the applied voltage and the anodizing time. To obtain the NWES, polytetrafluoroethylene (PTFT, Teflon®: DuPont™) replication based on the dipping method was used, with a PTFT solution (0.3 wt%). During replication, the polymer sticking phenomenon due to van der Waals interactions creates microscale bunch structures on the nanoscale wire-entanglement structures. This process provides a hierarchical structure with nanostructures on microstructures and enables commercialization. The diameter of the replicated wires was about 40 nm, and their lengths were 22–75 µm according to the anodizing time. The fabricated surface has superhydrophobicity; the apparent contact angle of the PTFT micro and nanostructures is about 160°–170° and the sliding angle is less than 1°.

An active vibration suppression system is designed using a multiobjective state-feedback controller. The governing equation of motion for a piezo/beam system is derived using Hamilton's principle. The control gains of the resulting system are selected using the theory of robust controls. In this regard, a robust controller is designed using a H 2 /H ∞ feedback control law that satisfies additional constraints on the closed-loop pole location in the face of model uncertainties, which are derived for a general class of convex regions of the complex plane. These constraints are expressed in terms of the linear matrix inequalities approach for multiobjective synthesis. The validity and applicability of this approach for vibration suppression for the piezo/beam system by damping out the multiple vibrational modes of the piezo/beam system are discussed.

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