Harvard Rotary 3D Printing Creates Soft Robots That Move Like Muscles

The Problem With Soft Robotics

Soft robots—flexible machines that can squeeze into tight spaces, handle delicate objects, and work safely alongside humans—have enormous potential. From surgical tools that navigate the body without damaging tissue to grippers that handle fragile produce, the applications are vast.

But building them has always been a headache. Traditional methods require complex molds, multi-step assembly, and painstaking alignment of internal channels that make the robots move. Want to change the design? Start over from scratch.

Harvard researchers have just changed that equation.

One Nozzle, Multiple Materials, Infinite Possibilities

The team at Harvard's John A. Paulson School of Engineering and Applied Sciences, led by Professor Jennifer A. Lewis, developed a rotational multimaterial 3D printing process that creates soft robots with programmable movement built directly into the print.

Here's how it works:

• Rotating nozzle: A single nozzle rotates as it extrudes, allowing precise placement of multiple materials in a single pass
• Dual-material filaments: An outer flexible shell (silicone-based elastomer) surrounds an inner gel (poloxamer) that can be flushed out later
• Embedded channels: Once the inner gel is removed, you're left with precisely engineered hollow channels
• Pneumatic actuation: Pump air through those channels, and the structure bends, twists, or grips in exactly the way it was designed to

The key innovation is controlling the asymmetry of the internal channels. By varying where the hollow space sits within each filament, the researchers can program exactly how the robot will deform when pressurised.

What Can You Print?

The Harvard team demonstrated several impressive structures:

• Soft grippers: Hand-shaped devices that close around objects when inflated
• Flower-like actuators: Petals that open and close in sequence
• Tendril-like structures: That twist and curl like plant vines
• Programmable bending: Strips that curve in predetermined directions

Because the motion is encoded in the geometry, no external control systems or complex wiring is needed—just air pressure.

Why This Matters

This isn't just a clever lab trick. It addresses fundamental challenges in soft robotics:

Rapid prototyping: Design iteration that once took weeks now takes hours. Print, flush, test, modify the CAD file, repeat.

Customisation: Each robot can be tailored to a specific application without retooling. A surgical robot for one procedure can be redesigned for another with a few mouse clicks.

Complexity without assembly: Traditional soft robots require gluing, bonding, or stitching together multiple components. This method prints everything in one go.

Biocompatibility: The silicone elastomers used are already FDA-approved for medical applications.

The Road Ahead

The research, published in Advanced Materials, represents a significant step toward practical soft robotics. The Harvard team envisions applications in:

• Minimally invasive surgery: Tools that navigate the body with unprecedented dexterity
• Rehabilitation devices: Custom-fitted assistive devices printed on demand
• Industrial handling: Grippers for delicate electronics, food, or pharmaceutical products
• Search and rescue: Soft robots that can squeeze through rubble to reach trapped victims

The Bottom Line

Harvard's rotational multimaterial 3D printing isn't just a new way to make soft robots—it's a fundamentally different approach to thinking about how machines move. By embedding actuation directly into the structure during fabrication, the researchers have eliminated the traditional divide between "the robot" and "its control system."

For makers and engineers, this points toward a future where designing a soft robot is as simple as drawing where you want it to bend, hitting print, and connecting an air line. The complexity lives in the geometry, not the assembly.

The paper is open access, and the Lewis Lab at Harvard has a track record of developing practical manufacturing techniques that eventually find their way into industry. Watch this space.