Microfiber SMPU film affords quicker shape recovery than the bulk one

Comparing to the bulk SMPU (shape memory polyurethane) film, microfiber SMPU film afforded much quicker and sharper shape recovery when heated in water bath. The shape recovery of the microfiber film only took ̃1/4 time of that needed for the bulk film from Rr (shape recovery ratio)=10% to Rr=90%. The final Rr and Rf (shape fix ratio) of the microfiber film was also enhanced. The microfiber film was fabricated by electrospinning with the fiber diameter of 200 nm to 1 μm. DSC and DMA results indicate that the formation of microfiber has very limited effect on the Ttrans (switching temperature) of the SMPU. The quick shape recovery of the microfiber SMPU film is considered due to the higher surface area of microfiber film that is favorable for quicker heating/cooling of the sample and quicker diffusion of water. This study offers a possible way to improve the shape recovery speed without changing the chemical composition, which may meet special needs for sensors or actuators of biomedical devices and others.