Liquid-repellent surfaces, such as superhydrophobic surfaces, superoleophobic surfaces, and slippery liquid-infused surfaces, have drawn keen research interest from the communities engaged in chemical synthesis, interfacial chemistry, surface engineering, bionic manufacturing and micro-nano machining. This is due to their great potential applications in liquid-proofing, self-cleaning, chemical resistance, anti-icing, water/oil remediation, biomedicine, etc. However, poor robustness and durability that notably hinders the real-world applications of such surfaces remains their Achilles heel. The past few years have witnessed rapidly increasing publications that address the robustness and durability of liquid-repellent surfaces, and many breakthroughs have been achieved. This review provides an overview of the recent progress made towards robust and durable liquid-repellent surfaces. First, we discuss the wetting of solid surface and its generally-adopted characterisation methods, and introduce typical liquid-repellent surfaces. Second, we focus on various evaluation methods of the robustness and durability of liquid-repellent surfaces. Third, the recent advances in design and fabrication of robust and durable liquid-repellent surfaces are reviewed in detail. Fourth, we present the applications where these surfaces have been employed in fields like chemistry, engineering, biology and in daily life. Finally, we discuss the possible research perspectives in robust and durable liquid-repellent surfaces. By presenting such state-of-the-art of this significant and fast-developing area, we believe that this review will inspire multidisciplinary scientific communities and industrial circles to develop novel liquid-repellent surfaces that can meet the requirements of various real-world applications.

Super-hydrophobic surfaces are attractive due to self-cleaning and anti-corrosive behaviors in harsh environments. Laser texturing offers a facile method to produce super-hydrophobic surfaces. However, the results indicated that the fresh laser ablated surface was generally super-hydrophilic and then gradually reached super-hydrophobic state when exposed to ambient air for certain time. Investigating wettability changing mechanism could contribute to reducing wettability transition period and improving industrial productivity. To solve this problem, we have studied the bare aluminum surface, fresh laser ablated super-hydrophilic surface, 15-day air exposed surface, and the aged super-hydrophobic surface by time-dependent water contact angle (WCA) and rolling angle (RA), scanning electron microscopy (SEM), 3D profile and X-ray photoelectron spectroscopy (XPS). The origins of super-hydrophilicity of the fresh laser ablated surface are identified as (1) the formation of hierarchical rough structures and (2) the surface chemical modifications (the decrease of nonpolar carbon, the formation of hydrophilic alumina and residual unsaturated atoms). The chemisorbed nonpolar airborne hydrocarbons from air moisture contributed to the gradual super-hydrophobic transition, which can be proved by the thermal annealing experiment. Particularly, to clearly explore the wettability transition mechanism, we extensively discussed why the laser-induced freshly outer layer was super-hydrophilic and how the airborne hydrocarbons were chemisorbed. This work not only provides useful insights into the formation mechanism of laser ablated super-hydrophobic surfaces, but also further guides industry to effectively modify surface chemistry to reduce wettability transition period and rapidly produce stable and durable super-hydrophobic surfaces.

This paper proposes the design of a novel 3-DOF monolithic manipulator. This manipulator is capable of performing planar manipulations with three kinematically coupled DOFs, i.e., the translations in the X and Y axes and the rotation about the Z axis. An improved Scott-Russell (ISR) mechanism is utilized to magnify the displacement of the piezoelectric actuator (PEA). Unlike the SR mechanism, a set of leaf parallelograms is incorporated into the drive point of the ISR mechanism as a prismatic joint. As a result, the linearity of motion and stability are improved. With circular flexure hinges being treated as revolute joints, the forward kinematics and inverse kinematics of the 3-DOF manipulator are analytically derived. Computational analyses are performed to validate the established kinematics models. Due to the unwanted compliance of the flexure hinges, the actual displacement amplification ratio of the ISR mechanism is smaller than its theoretical value. This is the main cause of the discrepancies between the analytical and computational results. The reachable workspace and the static/dynamic characteristics of the 3-DOF manipulator are also analyzed.

This paper presents a novel piezoelectrically actuated dual-axis micro manipulator with an asymmetric compliant structure. The mechanical design of the micro manipulator is first presented. A novel guiding bridge (GB)-type mechanism was proposed and utilized in the left part of the micro manipulator to improve the dynamic performance of the micro manipulator. The analytical model has been established based on pseudo-rigid-body (PRB) model and matrix-based compliance modeling (MCM) method. The kinematic and the precision of the micro manipulator have been analyzed, and the input and output couplings have been investigated. The prototype of the micro manipulator has been fabricated by wire electro discharge machining (WEDM). Then, open-loop experimental tests have been performed. The experimental results match well with the analytical calculation, and the amplification ratios are 11.12 and 4.64 for the left part and right part, respectively. Proportional-integral (PI) controller has been used to regulate the output displacement and grasping force, and a series of closed-loop experiments have been conducted to investigate the performance of the micro manipulator. The results show that the position resolution for both the right and left parts is 0.15 μm, and the force resolution is 4 mN.