Programmable Anisotropic Hydrogels with Localized Photothermal/Magnetic Responsive Properties

Programmable smart materials that can respond locally to specific stimuli hold great potential for many applications, but controllable fabrication of these materials remains challenging. This work reports the development of novel programmable anisotropic materials with both magnetic and photothermal stimuli-responsiveness, which are fabricated by anchoring thermosensitive poly(N-isopropyl acrylamide) (PNIPAm) and magnetic Fe₃ O₄ nanoparticles on the surface of MoS₂ nanosheets. Further embedding PNIPAm-MoS₂ /Fe₃ O₄ into 3D-printed hydrogel cubes results in stimuli-responsive building blocks, and the magnetic field can precisely control their orientation and near-infrared (NIR) light absorbing property. Particularly, the variation of the orientation of MoS₂ /Fe₃ O₄ block results in obvious changes of their photothermal efficiency and optical property. By exploiting the anisotropy of MoS₂ /Fe₃ O₄ and their NIR light responsiveness, thermally-induced phase transitions in individual 3D printed hydrogel building block can be locally controlled for magnetic field-assisted programming a quick response (QR) code. Alternatively, fluorescent QR code with high contrast and security level can be achieved by photothermal-induced release of fluorescent dyes. These 3D printed magnetically programmed hydrogels hold great potential for application in information storage, intelligent materials, and precise therapy.