The study asks how permanent micro-magnets can be reliably integrated into polymer microrobots during two-photon polymerization. The authors experimentally demonstrate direct printing around pre-aligned magnets in a helical swimmer, a MicroTumbler, a compliant micro-gripper, and a mini-MicroTumbler. A sputtered tantalum coating enables incorporation of initially uncoated 100 μm magnets. Bench-top measurements show frequency-dependent swimming and tumbling and field-controlled gripping; fixture arrays offer a route to unattended fabrication. Current throughput and further miniaturization are co

Place the magnet first. Print a polymer body around it. One fabrication idea opens the way to machines that swim, tumble and grip.

The magnet stays. The body takes shape.

Position

A fixture holds a permanent magnet in the right place and orientation.

Print around

A tightly focused laser hardens tiny volumes of resin into a connected polymer body.

Put it in motion

External magnetic fields act on the embedded magnet to move or deform the robot.

Small machines. Meaningful choices.

Print a body, find a swimmer’s sweet spot, then turn a magnetic field into a gripping motion.

Start with the magnet.

Choose a design. Watch polymer grow around a magnet that is already in place.

A single magnet and a taller body: DiLL provides the vertical printing range.

Position & align

Print shell & body

Develop & release

Fabrication follows Methods §2.2–2.3. Real structures are cured, developed and released after printing.

The body chooses the action. The same embedded-magnet strategy becomes a rigid helical tail, a hollow tumbler or compliant gripping arms.

Build around. Keep it together.

Inserting a magnet after printing can damage delicate structures. Printing around a pre-positioned magnet makes the robot one connected structure.

The fixture sets the geometry.

Magnets are placed manually in a printed fixture, aligned with marked pole directions, and checked under a microscope. Multiple magnets can have distinct positions and polarities.

Focused light builds the polymer.

Two-photon polymerization hardens small volumes of IP-S photoresist. The laser prints a shell around the magnet, then the rest of the microrobot body.

The surface makes a difference.

Uncoated 100 μm magnets showed bubbles and resin-edge retraction. A 0.5 μm sputtered tantalum coating enabled stable encapsulation.

The authors attribute the coating’s effect to smoother surfaces, improved wetting, less outgassing and better adhesion. Methods §2.6 ↗

Different bodies. Different possibilities.

The study fabricated and tested four microrobotic systems, showing the strategy across distinct geometries and environments.

Helical swimmer

A 250 μm magnet drives a two-turn helical ribbon. Forward propulsion peaked at 80 Hz; higher frequencies caused step-out.

MicroTumbler

A hollow body tumbles over its edges. Speed generally rose from 3 to 5 Hz on surfaces inclined by 0°, 5°, 15° and 30°.

Micro-gripper

Two opposite magnetic polarities let uniform fields open the arms. Field gradients move the gripper to rearrange micro-objects.

Mini-MicroTumbler

A tantalum-treated 100 μm magnet extends the method to smaller robots. Translational speed increased with actuation frequency.

From the lab to the evidence.

Explore the original figures: the fixtures, fabricated structures, measured motion and manipulation sequences.

A magnet-first fabrication workflow

Custom fixtures align magnets before printing. Dip-in and oil-immersion modes offer different geometry and alignment advantages. Surface treatment and microscope images show the process from shell to finished robot.

Look at panel c to compare the two printing modes, and panel g to see polymer bodies being printed around magnets.

Original figure reproduced from Yang et al. (2026), CC BY 4.0. Resized for display.

More control, inside smaller machines.

Placing magnets with chosen orientations offers a route to more complex microrobot architectures. The paper points toward targeted delivery and microscale assembly as future applications.

What was demonstrated Fabrication, bench-top locomotion and controlled object manipulation across four robot designs.

The authors plan to improve fabrication efficiency, optimize batch printing and pursue smaller magnetic components. They also propose long-term cyclic actuation and interface-stability studies.

A swimmer currently takes about 55 minutes to print; an array of nine may take over eight hours. Further miniaturization depends on magnet handling, alignment and optical tracking as well as material compatibility.

Generalized direct fabrication of embedded–magnet microrobots with enhanced material compatibility

Yang Yang, Jeremy B. Gan, Jialong Huang, Sven Mucke, Aaron C. Davis, Haiyan Wang & David J. Cappelleri

Journal of Micro-Bio Robotics · 2026 · doi:10.1007/s12213-026-00208-8 ↗

Paper figures: Yang et al., licensed under CC BY 4.0; resized for display. Graphical abstract: AI-generated conceptual illustration. Interactive models simplify geometry and slow motion; charts use approximate figure digitization. Scientific descriptions and experimental conditions follow the paper.

Yang et al. (2026) · CC BY 4.0 · resized for display. Zoom in and scroll to inspect the details.