Photothermal activation in the near infrared range for 4-dimensional printing using relevant organic dyes

International audience4D printing has become an exciting sector of 3D printing since its appearance in the 2010s. This technology consists in adding time as an extra dimension of 3D printing. Different stimuli can be used to modify a 3D object after the printing process such as solvent, temperature, magnetic field, electricity or light. In this paper, a 4D behaviour was investigated using NIR light in combination with a low amount of NIR organic dyes in-situ embedded in the 3D printed polymer. As a first step, the influence of several parameters on the photothermal effect generated have been followed such as the NIR dye structure, the NIR dye concentration, the irradiation wavelength, the light irradiance and the polymer matrix. Due to the light-triggered process, the deformation of the 3D printed object could be reversibly achieved in the presence of a NIR organic dye in a few amount of time (20 s). In fact, the photothermal effect in-situ generated in the 3D printed object allowed to reach a temperature above the Tg of the latter. This phenomenon has been highlighted with tensile tests. Indeed, these tests showed the passage of the 3D printed object from a glassy state to a rubbery state upon NIR irradiation. Finally, the photothermal effect produced was used to rapidly bond two parts of a broken 3D printed object