Minimally Invasive Surgery (MIS) is a growing field including both laparoscopic androbotic operations. Surgeons and engineers are making continual efforts to reduce the negative effects of procedures on patients. Reducing the size of the surgical instruments is one effective method pursued in this effort. When the instruments approach 3 mm in diameter, they reach a threshold where the entry incisions can be small enough that no scar is left on the patient. Laparoscopic instruments on this scale exist but typically lack wrist articulation and only have 1 degree of freedom (DoF). Alternatively, robotic surgical instruments can achieve high levels of dexterity but at a greater diameter. Smaller diameter robotic instruments employ snake wrists but this results in large swept volumes. There is a need for smaller robotic instruments with 3 DoF that preserve a small operational volume. Several unique challenges result when trying to develop small-scale instruments. Friction forces due to the relative motion of actuation cables and other parts in the mechanisms become more significant, as do the challenges of producing and assembling parts with extremely small features. These challenges have been limiting factors for the size of instruments. Traditional mechanisms use pin joints and pulleys which result in higher part counts and higher internal friction. To overcome these challenges, two alternative designs that reduce part count and minimize friction are presented as potential mechanisms that could be used as surgical instruments on the mesoscale (1-5 mm). Both designs implement rolling contact and gearing in place of pin joints and pulleys to realize their motion. Additionally, alternative manufacturing methods that are ideally suited to mesoscale production are presented. Micro metal laser sintering and composite carbon nanotude structures are shown to have the resolution required to create the detailed features necessary for these new designs. The result are two mechanisms suited to be produced as mesoscale, robotically actuated, surgical instruments. One of the two designs has been physically prototyped and has demonstrated clinical capabilities at 4 and 5 mm diameter instrument sizes.



College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering



Date Submitted


Document Type





surgical instruments, robotics, mesoscale, healthcare, medical devices