Harvard Engineers Develop Rotational 3D Printing Method for Programmable Soft Robots
Harvard researchers have introduced a multimaterial 3D printing technique that enables soft robots to bend and morph in predictable ways, potentially simplifying fabrication for surgical and assistive applications.
Engineers at Harvard University have developed a new 3D printing method that enables soft robots to bend and change shape in precisely programmed ways when inflated, offering a streamlined alternative to conventional mold-based fabrication.
The technique, described in a study published in Advanced Materials, relies on rotational multimaterial 3D printing to embed hollow pneumatic channels directly into flexible structures. The approach could simplify how soft robotic actuators and grippers are designed and manufactured, particularly for applications requiring biocompatibility and fine motion control.
Soft robotics has drawn sustained interest from healthcare, manufacturing, and assistive technology sectors because flexible materials are safer for interacting with humans and delicate objects. But controlling how these materials deform under pressure remains a persistent engineering challenge.
Printing Motion Into the Material
The research was led by graduate student Jackson Wilt and former postdoctoral fellow Natalie Larson in the laboratory of Jennifer Lewis, the Hansjorg Wyss Professor of Biologically Inspired Engineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences.
At the core of the advance is a dual-material printing nozzle capable of extruding two substances simultaneously. The system produces filaments with a polyurethane outer shell and a removable inner core made from a poloxamer gel, a material commonly found in cosmetic products.
As the nozzle rotates during printing, it precisely controls the orientation and placement of the inner gel channel within each filament. After the outer shell solidifies, the inner gel is washed away, leaving behind hollow, pressurizable pathways. When air is pumped into these channels, the structures bend or twist in predetermined directions.
“We use two materials from a single outlet, which can be rotated to program the direction the robot bends when inflated,” Wilt said in a statement released by Harvard. “Our goals are aligned with creating soft, bio-inspired robots for various applications.”
The ability to encode actuation behavior directly during printing eliminates the need for casting molds, layering materials, and manually embedding pneumatic networks, steps that have traditionally limited customization and scalability.
From Flat Patterns to Functional Grippers
To demonstrate the method’s flexibility, the team printed intricate structures including a spiral flower-like actuator and a five-fingered gripper with articulated “knuckles”. Each device was produced in a continuous printing process, with motion characteristics defined by nozzle rotation speed, filament geometry, and flow rate.
By adjusting these parameters, researchers can determine how much a structure bends, in which direction, and under what level of internal pressure. The result is a programmable mechanical response embedded at the fabrication stage.
The broader implication is a shift toward more automated and customizable soft robot production. Traditional fabrication often requires multiple casting steps and careful alignment of pneumatic channels between layers. In contrast, the Harvard approach prints structure and functionality simultaneously.
“In this work, we don’t have a mold,” Wilt noted. “We print the structures, we program them rapidly, and we’re able to quickly customize actuation.”
Implications for Medical and Assistive Robotics
Soft robots are particularly attractive in surgical and rehabilitation contexts, where rigid devices can pose safety risks. Flexible actuators that conform to tissue or assist human motion must deliver controlled, repeatable movement under constrained conditions.
By enabling predictable shape morphing through embedded channels, the rotational multimaterial technique could support next-generation surgical tools, wearable assistive devices, or adaptive grippers for delicate manufacturing tasks.
The work builds on prior innovations from the Lewis lab in multimaterial and helical 3D printing, where similar approaches were used to fabricate artificial muscle-like structures. The new method extends that foundation toward more complex, integrated soft robotic systems.
The research received federal funding support from the National Science Foundation through Harvard’s Materials Research Science and Engineering Center and from the U.S. Army Research Office’s MURI program.
As soft robotics continues to mature, advances in fabrication may prove as consequential as breakthroughs in control algorithms. By embedding motion logic directly into printed materials, Harvard’s approach suggests a future in which the mechanical intelligence of soft machines is designed at the nozzle level rather than assembled afterward.
