Characterizing electroactive polymers for use in minimally invasive surgical instruments

The popularity of minimally invasive surgical (MIS) procedures over traditional open procedures motivates us to develop new instruments that address the limits of existing technology and enable more widespread use of minimally invasive approaches. Robotic surgical instruments have the potential to provide improved dexterity and range of motion within the confines of the human body when compared with manually actuated instruments. The high strain response of electron-irradiated p(VDF-TrFE) copolymer makes it a candidate actuator material for robotic instruments that provide electronic mediation and multiple degrees of freedom of tip movement. We are currently studying both active and passive viscoelastic properties with the end goal of constructing a mathematical model to simulate the behavior of this material as an actuator. Studies have been conducted on 15 micron thick samples in rolled and rolled-flattened configurations. Active responses indicate approximately 2.5% strain in a 93 MV/m electric field under lightly loaded test conditions. Passive properties can be modeled by a 5 parameter viscoelastic model with two time constants of approximately 12 and 193 seconds. Current studies are examining means of combining active and passive properties in a simple model that can aid in design of a control system for the robotic actuators.