Compliant Mechanisms Research For Use in Surgical Devices

Compliant mechanisms transfer force or displacement through elastic body deformation. These are usually single-piece or jointless structures with certain advantages over rigid-body mechanisms. They are cheaper to mass produce, and have other advantages like not having backlash, and not requiring assembly. On the down side, because there is some stiffness, they don’t have high fidelity force feedback necessary for some hand tools, especially for use in minimally invasive surgery.

To get over this, we theorize a balancing compliant mechanism with the exact opposite stiffness can be attached. This project was a validation of that hypothesis. I did this for a summer research fellowship at Bucknell University under Prof. Charles Kim, and with MS student Karin Hoetmer from TU Delft.

I was responsible for designing and fabricating the apparatus used to test the mechanisms. The apparatus had to be frictionless and very precisely constrained, while measuring force and displacement of the mechanism.  I was also responsible for fabricating the mechanisms in the laser cutter, designing and running the experiments, and machining parts. In the end we showed that the concept was indeed possible.  Further, I made important discoveries about the manufacture of compliant mechanisms in a laser cutter.

A year later, our research was published!

Hoetmer, K., Woo, G., Kim, C., Herder, J., “Negative Stiffness Building Blocks for Statically Balanced Compliant Mechanisms: Design and Testing”, J. Mechanisms Robotics 2, 041007 (2010).