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Natural releasable attachment systems of insect legs, where attachment-detachment performances are often very fast, seem to be optimized to get a maximum of real contact to the substratum. Tarsi of Tettigonia viridissima bear flexible attachment pads with unusual ultrastructural architecture of the cuticle. The indentation of the attachment pads was measured under different loads using a force-tester. Since the mechanical properties are influenced by material structure, the freeze-substitution experiments were undertaken to investigate the influence of loads on material structure. Both profile changes of the surface and the orientation of cuticle microfibrils were visualized by means of scanning electron microscopy followed by fracturing of the frozen material. The results show that the flexible pad material deforms replicating the substrate profile down to the micrometer roughness. The pad material showed both elastic and viscous behavior under loads. Elastic deformation of the pad occurred under normal force applied for 4-6 s (elastic modulus 27.2 +/- 11.6 kPa). Two viscous relaxation processes were found, of time constants tau1 = 1.88+/-0.616 s and tau2 =41.2 +/- 9.95 s. Low stiffness of material studied here aids in surface replication and increase of area of real contact between the pad and the underlying substrate.

and S. Gorb, MPI fur Entwicklungsbiologie, Tiibingen, Germany Biological micro-and nanotribology is a new interdisciplinary field of research which draws on physics, chemistry, mechanics, and biology. The present work brings together information on friction, adhesion, and wear in biological systems and looks at applying this new knowledge to the design of, e.g., micro-electro-mechanical systems, the development of new types of monolayer lubrication, the invention of new adhesives, or the construction of artificial joints. Contents: Introduction; Physical principles of micro-and nanotribology; Biological frictional and adhesive systems; Frictional devices of insects; Microscale test equipment; Nanoscale probe techniques; Microscopy techniques; Samples, sample preparation, and tester set-up; Case study I: Indentation and adhesion; Case study 11: Friction; Case study 111: Material properties; Outlook; Appendix. ISBN 3-540-41 188-7 304 pp. hard cover E59.00 €79.95 Available from: Springer Handbook of Inpared Spectroscopy of Ultrathin FilmsValeri P. Tolstoy, kina Chernyshova, St. Petersburg State University, Russia, and Valeri A. Skryshevsky, National Shevchenko University, Kiev, Ukraine This handbook will serve as an authoritative reference on the growing use of infrared (IR) spectrometry to characterise very thin films at extended interfaces. Providing practical information on experimental methods, up-to-date theory, and considerable reference data, it is requisite reading for those wanting to measure and interpret IR spectra of ultra-thin films.Full discussion of the theory underlying the techniques Detailed information on equipment and accessories The first compilation of longitudinal frequencies of different substances New approaches, such as Surface Enhanced IR spectroscopy (SEIR), time-resolved FTIR spectroscopy, and high-resolution microspectroscopy using synchotron radiation.

Evolutionarily optimized frictional devices of insects are usually adapted to attach to a variety of natural surfaces. Orthopteran attachment pads are composed of hexagonal outgrowths with smooth £exible surfaces. The pads are designed to balance the weight of the insect in di¡erent positions and on di¡erent materials. In a scanning electron microscopy study followed by freezing^substitution experiments, the ultrastructural architecture of the pad material was visualized. In friction experiments, the interaction was measured between the attachment pad and a polished silicon surface. The inner structure of this material contains distally directed rods, branching close to the surface, and spaces ¢lled with £uid. The speci¢c design of the pad material provides a higher frictional force in the distal direction. Frictional anisotropy is more enhanced at higher normal forces and lower sliding velocities. It is concluded that optimal mechanical functionality of biosystems is the result of a combination of surface structuring and material design.

Design of attachment devices in insects varies enormously in relation to different functional loads. Many systems, located on different parts of the body, involve surfaces with particular frictional properties. Such systems evolved to attach parts of the body to each other, or to attach an insect to the substratum by providing fast and reversible attachment/detachment. Among these systems, there are some that deal with predefined surfaces, and others, in which one surface remains unpredictable. The first type of system occurs, for example, in wing-locking devices and head-arresting systems and is called probabilistic fasteners. The second type is mainly represented by insect attachment pads of two alternative designs: hairy and smooth. The relationship between surface patterns and/or mechanical properties of materials of contact pairs results in two main working principles of the frictional devices: mechanical interlocking, or maximization of the contact area. We give an overview of the functional design of two main groups of friction-based attachment devices in insects: probabilistic fasteners and attachment pads.