Synthesis of magneto-responsive microswimmers for biomedical applications

Interest in untethered mini and micro-robots has shown a significant increase lately, especially magneto-responsive swimmers. In this study, a soft sub-millimeter sized swimmer and a magnetic actuation system was developed. An extrusion-based 3D printer was used to form swimmers with three different types of magnetic content, Fe micro flakes and nanoparticles, and Nd-Fe-B micro flakes, were incorporated into polymeric bounder material. Using milli- and micro-swimmers in biological environments demands the use of cyto-compatible materials that would disguise the magnetic materials from the immune system. In this study, particles were encapsulated in a gelatin-alginate-cellulose based hydrogel. Next, these microswimmers were steered along a path via the magnetic gradient created by a custom-made electromagnetic system. The base of the electromagnetic system was designed using a CAD computer program and three dimensionally (3D)-printed. Consisting of four independent solenoids, each two controlling the movement on an axis, the system was designed to move the microswimmers in a certain path. The solenoids were controlled by Arduino microcontroller board. The electrical current applied to the electromagnetic device in all the trials was 2 amperes, which generates a magnetic field in between 100 to 376 Gauss throughout the experiment area. Thus, a magnetic gradient from the center to the pole of the solenoid was established. The magnetic and chemical behavior of these materials were compared based on their magnetic responsiveness and 3d printability. Developed magneto-responsive microswimmers could be used in biomedical robotics and drug delivery applications.