Electrospinning preparation of perylene-bisimide-functionalized graphene/polylactic acid shape-memory films with excellent mechanical and thermal properties

Electrospinning preparation of perylene-bisimide-functionalized graphene/polylactic acid composite films with shape-memory properties.

Hot Embossing of Micro-Pyramids into Thermoset Thiol-Ene Film

This paper presents the first attempt to texturize a fully crosslinked thermoset shape memory polymer using a hot embossing technique. UV-cured thiol-ene films were successfully embossed with anisotropically-etched Si (100) stamps at a temperature of 100 °C, which is about 50 °C above the glass transition temperature of the polymer. The low storage modulus of the polymer in a rubbery state allowed us to permanently emboss random micro-pyramidal patterns onto the surface of the film with high fidelity by applying 30 MPa pressure for 1 h. Atomic force microscopy (AFM) investigation showed perfect replication of the stamp micropattern with typical height of the largest inverted pyramids close to 0.7 µm and lateral dimensions in the range of 1–2 µm. Changes in surface roughness parameters of the embossed thiol-ene films after annealing them at 100 °C for 1 h or storing for 2 months in air at standard room conditions were negligible. The achieved results open new perspectives for the simple and inexpensive hot embossing technique to be applied for the micropatterning of prepolymerized thermoset shape memory films as an alternative to micropatterning using UV casting.

Al2O3 and Pt Atomic Layer Deposition for Surface Modification of NiTi Shape Memory Films

Pt coatings on NiTi film micro-actuators and/or sensors can add some useful properties, e.g., they may improve the NiTi anticorrosion and thermomechanical characteristics or activate surface properties beneficial for a specific application (e.g., functionalized surfaces for biomedical applications). Pt coatings prepared via atomic layer deposition (ALD) may help reduce cost due to the nanometric thickness. However, no authors have reported preparation of Pt ALD coatings on NiTi films, perhaps due to the challenge of the concurrent NiTi film oxidation during the Pt ALD process. In the present study, Al2O3 and Pt ALD coatings were applied to NiTi thin films. The ALD coating properties were studied using electron and atomic force microscopies and X-ray photoelectron spectroscopy (XPS). Potential structural changes of NiTi due to the ALD process were evaluated using electron microscopy and X-ray diffraction. The presented ALD process resulted in well-controllable preparation of Pt nanoparticles on ultrathin Al2O3 seed layer and a change of the transformation temperatures of the NiTi films.

Recovery Behavior of Microstructured Thiol-Ene Shape-Memory Film

In this work, surface microstructurization was coupled with shape-memory polymer to generate reversibly tunable surface properties. A photopolymerizable thiol-ene composition comprising a mixture of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT) and 2,2-dimethoxy-2-phenylacetophenone (DMPA) was used to prepare microstructured thiol-ene shape-memory film via casting and UV polymerization on the electron beam lithography fabricated arrays of 1 µm and 2 µm square pits. The mechanical deformation via compression and recovery of the surface microstructure were investigated. Results show that, after heat treatment of the deformed thiol-ene film, the recovery yields for microstructures were not worse than 90% ± 2% and 93% ± 2% for structures imprinted with 1 µm and 2 µm square pit micro imprint stamps. Additionally, heat treatment of deformed thiol-ene film resulted in the recovery of intense diffraction colors and laser diffraction patterns. This study opens up an avenue of incorporating microstructured shape-memory films for new products, e.g., optical security devices, superhydrophobic coatings, medical diagnostics and biosensors.