3D printed stimuli-responsive magnetic nanoparticle embedded alginate-methylcellulose hydrogel actuators

Magnetic hydrogels have a myriad of promising applications including soft electronics, flexible robotics, biomedical devices, and wastewater treatment. However, their potential is limited by conventional fabrication methods which impede creating convoluted geometries. 3D printing may replace traditional fabrication techniques as it has an ability to fabricate complex shapes using a wide variety of materials. A new 3D printing ink, a bionanocomposite based on alginate, methylcellulose and magnetic nanoparticles (MNPs) was used to print pre-designed high-quality 3D structures. Three-dimensional hydrogel constructs had good mechanical stability and exhibited responsiveness to an applied magnetic field. Inclusion of the MNPs within the hydrogel and its precursor (ink) influenced their rheological properties - and mechanical stability. MNPs were found to play dual roles: (1) as a nanofiller that interacts with polymer backbone and alters its physicochemical properties, and (2) as a function provider that renders a bionanocomposite magnetic. The magnetic ink allows for the fabrication of multi-material structures such as hydrogels with a magnetic nanoparticle gradient. 3D-printed objects can be remotely actuated via magnetic fields.