Operating methods for two‐way behavior shape memory polymer actuators without using external stress

Abstract

AbstractOperating methods for two‐way behavior shape memory polymer (SMP) actuators have been developed and characterized. Since the shape memory effect of the SMP is one way, an external force to deform the SMP has also been used in conventional SMP actuators. We propose two operating methods: the double SMP layer method and the single SMP layer method. The double SMP layer method uses the shape memory effects of two kinds of SMPs with different glass transition temperatures (Tg1 and Tg2, Tg1 < Tg2). In this method, after a memory shape relating to Tg1 is formed, the generated memory shape relating to Tg2 cancels the previous memory shape at Tg2, i.e. the memory shape of Tg2 is set to the reverse shape of the memory shape of Tg1. The single SMP layer method uses the shape memory effect and thermal contraction of the SMP while it is cooling. In this method, a generated memory shape above Tg is returned to the pre‐memory shape by thermal shrinkage of the SMP when the SMP is cooled down below Tg. SMPs of the polyurethane series are chosen for these actuators. We confirmed that the proposed operating principles functioned experimentally by using prototype actuators of a cantilever beam and examining their fundamental characteristics. These operating methods need only a temperature cycle of heating and cooling and are suitable for small actuators such as microelectromechanical systems (MEMS). © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.