Design Engineering

Researches develop hybrid rigid-soft robotic arm for surgical applications


General Medical Harvard soft robotics

Bio-inspired approach combines pop-up fabrication with soft robotics to enhance endoscopic surgeries.

When it comes to the latest medical equipment advancements, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a robotic arm for endoscopes.

Currently, when it comes to using flexible endoscopes, surgeons are challenged with attaching and using rigid surgical tools to manipulate or remove tissue in the parts of the body that are typically harder to reach. These tools limit the capabilities of the endoscope.

soft robot arm

Image courtesy of the Wyss Institute at Harvard University

The new robotic arm for endoscopes includes integrated sensing, flexibility, and multiple degrees of freedom.

The research team designed the arm using a manufacturing paradigm based on pop-up fabrication and soft lithography. This enables the tool to lie flat on an endoscope until it arrives at the desired spot, then pops up to assist in surgical procedures.


Soft robotics pairs well with surgical applications because the devices can be matched with the stiffness of the body, ensuring they will not puncture or tear body tissue. However, at small scales, soft materials cannot generate enough force to perform surgical tasks. This is one of the big challenges that researchers are currently faced with.

“At the millimeter scale, a soft device becomes so soft that it can’t damage tissue but it also can’t manipulate the tissue in any meaningful way,” said Tommaso Ranzani, a postdoctoral fellow at SEAS and the Wyss Institute and coauthor of the paper.

One of the big questions going forward is how can soft robotics be designed and developed so that they are able to generate the needed force while ensuring safety limits.

The team developed a hybrid model that used a rigid skeleton surrounded by soft materials. The manufacturing method drew on previous work in origami-inspired, pop-up fabrication, developed by Robert Wood, the Charles River Professor of Engineering and Applied Sciences.

Relying on current methods, the team integrated soft actuators into the pop-up system.

“We found that by integrating soft fluidic microactuators into the rigid pop-up structures, we could create soft pop-up mechanisms that increased the performance of the actuators in terms of the force output and the predictability and controllability of the motion,” said Sheila Russo, postdoctoral fellow at SEAS and Wyss and lead author of the paper.

The soft actuators are powered by water. They are connected to the rigid components with an irreversible chemical bond, without the need of any adhesive. The team demonstrated the integration of simple capacitive sensing that can be used to measure forces applied to the tissue and to give the surgeon a sense of where the arm is and how it’s moving.

The arm is also equipped with a suction cup to safely interact with tissue. The team tested the device ex vivo, simulating a complicated endoscopic procedure on pig tissue. The arm successfully manipulated the tissue safely.

ex vivo surgery arm

Soft pop-up arm performing tissue counter-traction during an ex-vivo test on a porcine stomach (Image courtesy of Harvard University)

The fabrication method allows for increased levels of complexity for more sensing or actuation. All materials used are biocompatible.

The researchers demonstrated that the device could be scaled down to 1 millimeter, which would allow it to be used in even tighter endoscopic procedures, such as in lungs or the brain.

Next, the researchers hope to test the device in vivo.

“Our technology paves the way to design and develop smaller, smarter, softer robots for biomedical applications,” said Russo.

The research is described in Advanced Materials Technologies.


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