Gecko adhesion has inspired the fabrication of various dry adhesive surfaces, most of which are developed to be used under atmospheric conditions. However, applications of gecko-inspired surfaces can be expanded to vacuum and even space environment due to the characteristics of van der Waals interactions, which are always present between materials regardless of the surrounding environment. In this paper, a controllable, anisotropic dry adhesion in vacuum is demonstrated with gecko-inspired wedged dry adhesive surfaces fabricated using an ultraprecision diamond cutting mold. The adhesion and friction properties of the wedge-structured surfaces are systematically characterized in loading-pulling mode and loading-dragging-pulling mode. The surfaces show significant anisotropic adhesion (P ad ≈ 10.5 kPa vs P ad ≈ 0.7 kPa) and friction (P f ≈ 50 kPa vs P f ≈ 30 kPa) when actuated in gripping and releasing direction, respectively. The wedge-structured surfaces in vacuum show comparable properties as exposed in atmosphere. A three-legged gripper is designed to pick up, hold, and release a patterned silicon wafer in vacuum. The study demonstrates a green, high-yield, and low-cost method to fabricate a reliable and durable mold for gecko inspired anisotropic dry adhesive surfaces and the potential application of dry adhesive surface in vacuum.

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The gecko exhibits remarkably swift and reliable climbing ability on most surfaces in nature. Numerous studies have been conducted to determine the underlying mechanisms of gecko adhesion in order to realise controllable gecko-inspired handling applications. This paper, reviews recent developments in the field of gecko-inspired dry adhesive surfaces from fabrication to application. First, the gecko adhesion progress, from the adhesive tools and the source of adhesion to the underlying mechanisms of tuning contact area and peeling behavior, is introduced. Then, the design and fabrication of gecko-inspired dry adhesive surfaces are comprehensively reviewed according to the three features of gecko adhesion, namely adaptability, controllability, and self-cleaning. Further, existing test methods for adhesion, friction and anisotropy are summarised, and the influences of test conditions such as the stiffness of test system, the area of the samples and the experimental environment are discussed. Finally, applications of robots and grippers based on the flexibly controllable adhesion and friction of gecko-inspired dry adhesive surfaces as well as novel controllable functional adhesive surfaces are introduced, and the associated control mechanisms are summarised.

The subpial technique extends the resection beyond the contrast enhancement and is associated with an overall survival beyond that seen in similar series where resection of the enhancement portion is performed. The effect of supratotal resection on survival exceeded the effects of age, Karnofsky performance score, and tumor volume. A prospective study would help to quantify the impact of the subpial technique on quality of life and survival as compared to a traditional resection limited to the enhancing tumor.