Thermomechanical characteristics of a shape memory polymer for a variable stiffness mechanism in medical applications

Abstract

Chancing rigidity of material or structure as necessary is useful for medical applications. Especially, in the colonoscopy, when a flexible endoscope traverses the tortuous path of large intestine, the structure of endoscope should be enough to flexible to pass through the path and reach a target point where a tumor or damaged tissue is located. On the other hand, if the endoscope navigates at the sigmoid flexure of colon or handles a tumor physically, then it should be stiff to maintain its configuration or support interaction load between the endoscope and tumor. One of the approaches to develop the variable stiffness mechanism is utilizing phase transition of materials such as low melting point alloy or thermoplastics. Considering the working environment of endoscope in human body, we have focused on a shape memory polymer that has low glass transition temperature near body temperature (38 ℃ at the large intestine) and safe for human. The thermomechanical characteristics of the shape memory polymer are investigated by differential scanning calorimeter, thermal diffusivity measurements, thermomechanical analysis, dynamic mechanical analysis, and tensile test. Utilizing the thermomechanical characteristics of shape memory polymer, we try to develop a novel endoscope with variable stiffness mechanism.