Abstract
Shape memory polymers are attractive smart materials that have many practical applications and academic interest. Three-dimensional (3D) printable shape memory polymers are of great importance for the fabrication of soft robotic devices due to their ability to build complex 3D structures with desired shapes. We present a 3D printable shape memory polymer, with controlled melting and transition temperature, composed of methacrylated polycaprolactone monomers and N-Vinylcaprolactam reactive diluent. Tuning the ratio between the monomers and the diluents resulted in changes in melting and transition temperatures by 20, and 6 °C, respectively. The effect of the diluent addition on the shape memory behavior and mechanical properties was studied, showing above 85% recovery ratio, and above 90% fixity, when the concentration of the diluent was up to 40 wt %. Finally, we demonstrated multi-material printing of a 3D structure that can be activated locally, at two different temperatures, by two different stimuli; direct heating and light irradiation. The remote light activation was enabled by utilizing a coating of Carbon Nano Tubes (CNTs) as an absorbing material, onto sections of the printed objects.
Highlights
Among smart materials, shape memory polymers (SMP) attract great interest in the general field of materials science and, in particular, in soft robotics [1,2,3,4,5]
In combination with 3D printing techniques, SMPs can be used for fabrication of objects with complex geometry, which are capable of shape change and movement; this approach is referred to as four-dimensional (4D) printing
polycprolactone methacrylated (PCLMA), the melting temperature is 56 ± 2 ◦ C while for a composition containing 50 wt % NVCL, the melting temperature decreases to 38 ± 1 ◦ C, which is similar to the melting temperature of pure
Summary
Shape memory polymers (SMP) attract great interest in the general field of materials science and, in particular, in soft robotics [1,2,3,4,5]. The common technology for multi-material printing is Polyjet printing [18,22,27], a major limitation of this approach is the requirement to utilize only low-viscosity commercial materials Another unique way for multi-material printing is vat polymerization, in which either, the exposure time of the material can be controlled locally, as presented by Zhang et al [23], or by replacing the vat during the printing process, as described by Ge et al [25]. The reversible process of opening and closing a box is performed by developing 3D objects, composed of two materials having different transition temperatures. We present multi-material 4D printing of SMP with tailored transition and melting temperature that can be activated both by direct heating and by light irradiation. The box can be activated by direct heating or by light which enables remote activation
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