New Materials and Approaches for 2D and 3D Printing of Responsive Objects

4D printing is a novel approach that enables dynamic functionality in printed objects. The objects can change their shape and dimensions in response to time or external triggers such as heat, electric and magnetic fields. We will describe various materials-driven approaches which enable fabrication of printed responsive objects and devices, mainly based on inks composed of polymers and monomers with dispersed nanomaterials, such as carbon nanotubes and magnetic particles. The polymers are obtained by localized photopolymerization reactions, thus enabling printing by stereolithography processes, such as in Digital Light Processing printers. Various responsive printed objects will be presented, in which the polymer itself is responsive, such as shape memory polymers, or the response results from embedded particles such as carbon nanotubes or magnetic particles. Such examples are methacrylated oligomers having a shape memory behavior, or stretchable urethan acrylate monomers that change shape under heat, a magnetic field or upon exposure to light at a specific wavelength due the presence of magnetic or plasmonic nanoparticles, respectively. The various inks will be demonstrated mainly as actuators for soft robotics.