Shape memory thin films of polyurethane: Synthesis, characterization, and recovery behavior

Abstract

Polyurethane thin films with inherent two phase segregated characters are exceptional candidates for the development of shape memory materials. However, controlling the phase behavior of such complex structures for decoding their recovery behavior still experiences its early stage of development. In this work, polyurethane thin films were synthesized based on two polyols, ester‐based polyols (ESP), and ether‐based polyols (ETP) together with diphenyl diisocyanate (MDI). The effects of ingredient ratio of PETP (ether‐based prepolymer)/PESP (ester‐based prepolymer) on the chemical structure and final properties of polyurethanes were studied by the Fourier‐transformed infrared spectroscopy (FTIR), the differential scanning calorimetry (DSC), the scanning electron microscopy (SEM), the dynamic mechanical thermal analysis (DMTA), a tensiometer, and the atomic force microscopy (AFM). The shape memory behaviors were explored by the thermomechanical cycles applied by a DMTA device in the controlled force mode. The PU films showed various properties compared with the bulk PU since they formed spherulitic textures with different structures. All the PU films except PU‐0 showed high shape recovery ca. 90% in the first cycle with a large glassy storage modulus in the range of 2,800–4,040MPa, and a recovery ratio enhanced by increasing the number of cycle to a maximum of 95%.

Bioprinting in Microgravity

“…Bioprinting is an extension of traditional 3D printing, functioning on the same core additive manufacturing processes, in which material is appended to the print in cumulative layers to shape 3D products. − Rather than printing with resin or thermoplastics, bioprinters are designed for compatibility with cell-laden bioinks. , Bioprinters utilize various bioinks, including extrusion-based printing using filaments, laser-assisted bioprinting, and inkjet printing of liquid droplets . Through the advances in materials especially polymers, − 3D printing has been established in biomedical applications. ,− Bioprinting has also many tissue engineering and regenerative medicine applications, including, but not limited to, organ-on-a-chip devices for medical and pharmaceutical research − and in vitro models of disease tissues such as tumors for cancer research, human tissue regeneration such as bone, skin, blood vessels, cartilage, and even internal organs to replace those which are damaged or diseased, ,− stem-cell research, − and organoid creation . 3D-bioprinting can enable producing complex 3D structures to mimic the in vivo microenvironment. − With a growing request for scaled-up readily available biomimetic organs and tissues, advances in bioprinting technologies are increasingly imminent and necessary to provide high-throughput, precise construction of cell-laden structures. − …”