The effects of self-assembled monolayer (SAM) and perfluoropolyether (PFPE) lubricant on the wear characteristics of flat silicon tips were investigated. The wear test consisted of sliding the silicon tips fabricated on a flat silicon specimen against SAM and PFPE (Z-tetraol) coated silicon (100) wafer. The tips were slid at a low speed for about 15 km under an applied load of 39.2 lN. The wear volume of the tip was obtained by measuring the tip profile using an Atomic Force Microscope (AFM). It was found that the coatings were effective in reducing the wear of the tips by an order of magnitude from 10 -6 to 10 -7 .

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In recent years, efforts to develop micro-robots for medical applications have been expanding. One of the key design issues in such micro-robots is to attain adequate frictional interaction between the robotic foot and the organ tissue. Particularly, it is important to generate the necessary frictional force without damaging the tissue. In this work, a design for the robotic foot was developed based on the frictional behavior of a tube structure. Fundamental experiments were initially performed to understand the bio-tribological behavior of a single tube. Then the design was modified to a multi-foot structure to achieve adequate friction. Bio-tribological investigation of a multi-tube foot in contact with a small intestine specimen of a pig was conducted. Friction tests were conducted using a pin-on-reciprocator type bio-tribotester. It was found that the multi-tube foot shows stick-slip behavior when slid against the small intestine specimen. The major mechanism behind the stick-slip behavior was due to interlocking between the tubes and the surface structures of the intestine specimen. Results of this work may be utilized for optimum design of frictional surface of medical micro-robots and other biological devices.

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