Biotribological investigation of a multi-tube foot for traction generation in a medical microrobot

In recent years, efforts to develop microrobots for medical applications have been expanding. One of the key design issues in such microrobots is to attain adequate frictional interaction between the robotic foot and the organ tissue. In particular, it is important to generate the necessary frictional force without damaging the tissue. In this work, a design for the robotic foot was proposed on the basis of the frictional behaviour of a tube structure. Fundamental experiments were initially performed to understand the biotribological behaviour of the tube and rod structures. The design was then modified to a multi-tube structure to achieve adequate frictional behaviour. Biotribological investigation of a multi-tube foot in contact with a small intestine specimen of a pig was conducted using a pin-on-reciprocator type biotribotester. It was found that there is an optimum number and arrangement of the tubes for generating high frictional force. Experimental results showed that a nine-tube foot had the highest initial friction coefficient of about 1.5. The major frictional mechanism was determined to be interlocking between the tubes and the surface structures of the intestine specimen. The results of this work will aid the optimum design of frictional surface for medical microrobots and other biological devices.