New 3D-printing method gives soft robots sense of touch

This research represents a foundational advance in emerging field of soft robotics.
Written by Greg Nichols, Contributing Writer

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering have figured out how to make soft robots with embedded touch sensing.

Soft robots built from highly-compliant materials are being investigated for a variety of tasks, including invasive surgery, exoskeleton suits, and for a theoretical class of safe industrial robotic pickers.

Because they can take different shapes to suit their environment, soft robots have the potential to be far more application-flexible than their rigid counterparts while also being safer for human workers.

But embedding sensors inside soft robots is problematic since most sensors are rigid.

Responding to that challenge, the Harvard researchers developed a kind of conductive ink that can be 3D printed within squishy substances.

The liquid-based ionic ink is incorporated during a process known as embedded 3D printing, which enables engineers to intricately combine multiple materials into an integrated final product.


The team created a soft robotic gripper with three fingers to test their ink-based sensor. When a finger is deformed after contacting a substance, the conductive ink beneath signals the input to the robot's actuator.

"To date, most integrated sensor/actuator systems used in soft robotics have been quite rudimentary," according to Michael Wehner, co-author of a paper about the breakthrough published in the journal Advanced Materials. "By directly printing ionic liquid sensors within these soft systems, we open new avenues to device design and fabrication that will ultimately allow true closed loop control of soft robots."

Indeed, the arrival of integrated sensors could signal a day not so far away when a functional robot, including all actuators and sensors, is 3D printed in a single session.

The prices for such robots would be much lower than prices for even simple robots today, potentially fomenting worldwide rapid adoption.

So far, the ionic ink sensors have been shown capable of sensing light and deep touch, temperature, curvature, and inflation pressure.

Potential uses include versatile robotic pickers for industry and agriculture and safe end effectors for robotic surgery.

Editorial standards