This paper describes an advanced tool guiding system for robot assisted surgery. It is offering two additional local degrees of freedom to a standard robotic tool guiding system like of the Zeus robotic surgery system. The tool guide is basically a tube that guides the inserted surgical instrument to the desired location. By adding two bending degrees of freedom at the tip, the developed system largely increases the maneuverability of the instrument. It consists of a micromachined superelastic tube driven by a conventional cable system. Main issue was the design of a flexible hinge system in superelastic NiTi that offers the desired bending angles (at least 90 degrees in both directions) and that is compatible with the material limits for long-time cycling. Based on extended FE calculations and experimental measurements the second-generation design offers 90 degrees bending in both directions. The improvement over previous devices is the combination of two degrees of freedom with a small diameter of only 5 mm. An additional advantage is the tool channel, which enables the use of different instruments with this single device.

This paper analyses scale effects for actuator types which are strong candidates for micro-actuation: shape memory alloys (SMAs), electrostatic, electromagnetic and piezoelectric actuators. SMA actuators are studied in detail and compared to the other actuator types on a basis of force, response time, and power density. Much of the analysis is based on thermal aspects and scaling effects on both convective and conductive heat transfer, which is a quite novel approach. Results of this thermal analysis are effects on surface temperature and maximum current density of microactuators.