Automated Fabrication of Magnetic Soft Microrobots

TL;DR

The paper addresses the critical problem of fully automated fabrication of soft magnetic microrobots with programmable three-dimensional magnetization directions. It introduces an updated SLA-based printer that replaces a UV LED approach with a compact $405\text{ nm}$ laser, a near-UV flat-top beam shaper, and a fused silica mirror to produce square voxels of size $50\,\mu\text{m} \times 50\,\mu\text{m}$, down from the previous $1.6\text{ mm}$ diameter voxels. By integrating optical and magneto-mechanical simulations (COMSOL) and an algorithm that maps COMSOL data to G-code for automated execution on a Raspberry Pi, the approach demonstrates validated designs such as a worm, gripper, and zipper under realistic magnetic actuation. The work promises higher accuracy, faster production, and better reproducibility for biomedical and other applications of soft magnetic microrobots, while outlining concrete future characterization steps to finalize the autonomous fabrication pipeline.

Abstract

The advent of 3D printing has revolutionized many industries and has had similar improvements for soft robots. However, many challenges persist for these functional devices. Magnetic soft robots require the addition of magnetic particles that must be correctly oriented. There is a significant gap in the automated fabrication of 3D geometric structures with 3D magnetization direction. A fully automated 3D printer was designed to improve accuracy, speed, and reproducibility. This design was able to achieve a circular spot size (voxels) of 1.6mm in diameter. An updated optical system can improve the resolution to a square spot size of 50$μ$m by 50$μ$m. The new system achieves higher resolution designs as shown through magneto-mechanical simulations. Various microrobots including 'worm', 'gripper' and 'zipper' designs are evaluated with the new spot size.

Figures (9)

• Figure 1: Magnetic torque and force illustration in a non-uniform magnetic field generated from an external permanent magnet.
• Figure 2: Assembly of the updated optical system for the 3D printer.
• Figure 3: Improvements to output intensity distribution with the addition of a beam shaper.
• Figure 4: Housing for the new optical system: a) Fused silica broadband dielectric mirror mounting seat. b) NUV flat top beam shaper double clamping case. c) Pigtailed laser diode fiber tail clamp. d) LD/TEC mount.
• Figure 5: COMSOL optics simulation. a) Optics set up with laser beam simulation. b) Confirmed voxel output shape. c) Voxel shape and size evolution.