Fundamental Study of a Position-keeping Module Using a Shape-memory Polymer

Abstract

Above their glass transition temperature, shape-memory polymers (SMPs) can be deformed by applying a small load. They maintain their shape after they have been cooled below the glass transition temperature, and then return to a predefined shape when heated above the glass transition temperature. The reversible change in the elastic modulus between the glassy and rubbery states of SMPs can be of the order of 100 to 1000 times. Exploiting these characteristics, this study seeks to evaluate the fundamental performance of a position-keeping module that uses an SMP. When this position-keeping module is warmed above its glass transition temperature, the SMP deforms and the module deforms on applying a small load. After the position-keeping module reaches a desired length, it is cooled to below the glass transition temperature and the SMP can be fixed in a rigid state without supplying electric power. The experimental results of a preliminary proof-of-concept investigation conducted on SMP tubes confirm the feasibility of using an SMP to fabricate a reliable, light and low-cost position-keeping module for a robot arm.