Rapid 3D Printing Magnetically Active Microstructures with High Solid Loading

The capability of fabricating magnetically active 3D microstructures is crucial for miniaturization of microrobots or microactuators. While additive manufacturing using magnetic nanoparticle-infused polymer resin offers the highly desirable precision and flexibility, the difficulty in handling resin with higher solid loading of magnetic nanoparticles needed to maximize the magnetic actuation forces remains to be the main obstacle. The increased viscosity of the magnetic resin not only significantly reduces the fabrication speed, but also makes the process vulnerable to the precipitation of the suspended magnetic nanoparticles. Herein, a comprehensive solution that synergizes the optimization of magnetic photopolymerizable resin and the high-speed 3D printing using microcontinuous liquid interface production (μCLIP) process is reported. An optimized magnetic photopolymerizable resin with 30 wt% solid loading of Fe₃O₄ nanoparticles is well dispersed over 72 h. Process characteristics of the magnetic photopolymerizable resins with variation in the solid loading of magnetic nanoparticles are investigated experimentally. The capability of 3D printing centimeter-size samples with sub-75 μm fine features using high solid loading (30 wt%) is also demonstrated. The increased printing speed using μCLIP significantly reduces the fabrication time to the order of minutes to hours, making the process more robust against the precipitation of the magnetic particles.