Near-infrared light-responsive shape-memory poly(ɛ-caprolactone) films that actuate in physiological temperature range

Near-infrared (NIR) light-responsive shape-memory films were prepared through the photo-initiated polymerization of poly(ɛ-caprolactone) (PCL) macromonomers with acryloyl terminal groups in the presence of gold nanorods (AuNRs). To incorporate the AuNRs homogenously within the films, the surfaces of AuNRs were also modified with PCL via surface-initiated ring-opening polymerization. The shape-switching temperature of PCL was adjusted in the physiological temperature range by controlling the melting temperature of PCL. Exposure to NIR light successfully induced the photothermal heating of embedded AuNRs and, consequently, the shape-switching transition. After NIR irradiation at higher-power densities, the film completely recovered its original shape. When exposed to lower-power densities, a local temperature increase was observed in the area where the beam hit. Therefore, local shape memory transformations were obtained. These results show the potential of gold nanorod-embedded PCL films as spatially controllable, shape-memory materials that actuate in physiologically relevant temperature ranges and from remote stimuli.