Superparamagnetic microrobots: fabrication by two-photon polymerization and biocompatibility

This work presents the fabrication and controlled actuation of swimming microrobots made of a magnetic polymer composite (MPC) consisting of 11-nm-diameter magnetite (Fe 3 O 4 ) nanoparticles and photocurable resin (SU-8). Two-photon polymerization (TPP) is used to fabricate the magnetic microstructures. The material properties and the cytotoxicity of the MPC with different nanoparticle concentrations are characterized. The live/dead staining tests indicate that MPC samples with varied concentrations, up to 10 vol.%, have negligible cytotoxicity after 24 h incubation. Fabrication parameters of MPC with up to 4 vol.% were investigated. We demonstrate that the helical microdevices made of 2 vol.% MPC were capable of performing corkscrew motion in water applying weak uniform rotating magnetic fields.