R.M. Sun; A.Y. Chen; Y. Ji; D.W. Yee; C.M. Portela
arXiv (2025) :2510.07599
Magnetic remote actuation of soft materials has been demonstrated at the macroscale using
hard-magnetic particles for applications such as transforming materials and medical robots.
However, due to manufacturing limitations, few microscale magnetically responsive devices
exist—light-based additive manufacturing methods, which are ideal for realizing microscale
features, struggle with light scattering induced by the magnetic particles. Moreover, large
hard-magnetic microparticles prevent high-resolution features from being manufactured al-
together, and soft-magnetic nanoparticles require impractically high loading and high mag-
netic gradients, incompatible with existing printing techniques. Among successfully fabri-
cated microscale soft-magnetic composites, limited control over magnetic-particle loading,
distribution, and matrix-phase stiffness has hindered their functionality. Here, we combine
two-photon lithography with iron-oxide nanoparticle co-precipitation to fabricate 3D-printed
microscale nanocomposites having features down to ∼8 µm with spatially tunable nanopar-
ticle distribution. Using uniaxial compression experiments and vibrating sample magnetom-
etry, we characterize the mechanical and magnetic properties of the composite, achieving
millimeter-scale elastic deformations. We control nanoparticle content by modulating laser
power of the print to imbue complex parts with magnetic functionality, demonstrated by a
soft robotic gripper and a bistable bit register and sensor. This approach enables precise con-
trol of structure and functionality, advancing the development of microscale metamaterials
and robots with tunable mechanical and magnetic properties.