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Measurements of the stress – strain response of hairlike gecko setae are presented. These setae have diameters in the micron range and are part of the attachment organs that enable lizards to cling to surfaces. Three test methods were employed: (a) applying tension with a piezoresistive cantilever inside a focused ion beam microscope under vacuum conditions, (b) three-point bending in air using an atomic force microscope, and (c) nanoindentation tests on the circumference of the seta. Elastic moduli were found to depend strongly on the method of testing: Tensile testing in vacuum yielded an elastic modulus of 7.3 ± 1.0 GPa which was roughly five to six times higher than in bending and in nanoindentation tests at ambient conditions. The results are discussed in terms of the anisotropic nanostructure of the setae and humidity effects. They constitute valuable input parameters for optimizing the performance of artificial attachment devices.

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Nanoparticles are essential building blocks for nanotechnology. In this paper we demonstrate a novel method to create nanoplatelets by thin film cracking. The thickness of the resulting platelets is determined by the film thickness, and their aspect ratio is controlled by the total strain and the elastic mismatch between substrate and thin film. Platelets can be created from any brittle film independently of microstructure and materials class. The feasibility of this method is substantiated by a statistical analysis of the fracture process.

Insects and geckos can climb walls because their feet have brushlike structures composed of miniscule hairs that act as adhesives. Emulating this exceptional and reversible adhesion in novel artificial attachment devices has become a very competitive area of research. Potential applications include allpurpose adhesive tapes and industrial grippers. Since the hairs are microscopic in size, their mechanical properties, such as strength and stiffness, have not yet been determined. Using a focused ion beam (FIB) microscope as an in situ laboratory for sample preparation, fixation, and testing, we have developed a new method for measuring the mechanical properties of samples that are a few tens of micrometers in length and a few micrometers in diameter. Applying this method, we show that individual hairs of the beetle Gastrophysa viridula have mechanical properties comparable to manmade materials. With this knowledge, the functioning of hairy attachment systems can now be modeled and emulated accurately. We believe that these measurements represent a major step in the development of biomimetic adhesive devices.The mechanical performance of biological systems relies on very specific ultrastructural features. Examples include the attachment devices of insects and geckos, which have recently received a great deal of research attention. [1][2][3] The adhesive pads of these attachment devices are unique in that they are covered by finely structured contact elements. These hairs, or setae, form a brushlike structure and end in contact elements having an area of only a few square micrometers. In insects, the pads themselves consist of a chitin-fiber composite known as insect cuticle, whereas in geckos the pads consist of keratin. In insects, the setae on these pads are from several tens to a hundred micrometers in length and a few micrometers in diameter, whereas in geckos they have a hierarchical structure ending in contact elements having dimensions in the sub-micrometer range. In each species, the setae terminate in spatulae, which adhere to almost any surface by van der Waals forces. [2,3] Models have been developed to describe the adhesion of such attachment devices based on the Johnson-Kendall-Roberts (JKR) theory of contact mechanics. [4,5] Most recently, adhesion design maps have been developed that delineate the material properties and dimensions required for optimal adhesion. [6] According to these maps, the Young's modulus, tensile strength, and seta radius are crucial parameters for the performance of the attachment devices. Measurements of these mechanical parameters for single setae have not yet been reported. What are the difficulties in measuring the mechanical properties of individual setae and similar structures? The complex geometry of these structures and the associated difficulties in handling during sample preparation, as well as their small size, which results in stringent requirements on strain and force resolution, create the need for in situ microscopy observations. Existing devices for mechanical t...

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