As robots become increasingly integrated into human environments like hospitals, homes and workplaces, a major challenge is ensuring they interact safely and intuitively with people in close proximity. A team of researchers at the University of Illinois Urbana-Champaign has demonstrated a novel solution: 3D printed soft robot skin that doubles as an embedded touch sensor.

The innovative skin pads, described in the journal IEEE Transactions on Robotics, are made from inexpensive thermoplastic urethane and can be easily customized and manufactured using standard 3D printers. When integrated onto a robotic arm or gripper, the air-tight pads deform when pressed, activating internal pressure sensors that detect touch, grip force, and environmental contact.

"Robotic hardware involves large forces, so it needs to be safe around humans," said Joohyung Kim, the project's lead and an electrical and computer engineering professor. "Soft skin can provide mechanical compliance for safety while also enabling tactile sensing - an often overlooked robotic sensing modality."

Toward Intuitive Human-Robot Interaction Beyond just safety benefits, the soft touch sensors could enable robots to recognize and respond to human physical interactions like tapping, prodding, or applied forces as intuitive instructional inputs. In their study, the researchers showcased scenarios where contact detected near a robot's joints automatically stops motion to prevent collisions or injury.

"We've shown functional, cost-effective alternatives to traditional tactile arrays can be 3D printed," Kim said. "Since it's just reprogramming the printer, the technique is highly customizable across different robotic systems."

The manufacturing advantages of 3D printing the flexible sensor pads could accelerate their adoption in human-centered environments like hospitals, where replaceable, sanitizable components are highly desired. Kim envisions future robots with interchangeable 3D printed skins that are easily swapped for cleaning or repair.

"Imagine you want soft-skinned robots assisting in hospitals - the skins would need regular sanitizing or replacement, both very expensive with conventional manufacturing," said Kim. "But 3D printing provides scalable fabrication of inexpensive, interchangeable parts."

A New Sensing Frontier for Robotics While robot vision and language models have advanced rapidly, Kim noted that physical "force-level" interactions have remained an understudied sensing modality despite their intuitive appeal and importance in dexterous manipulation.

"From the robot's view, force data is its most direct interaction with the environment," he said. "But there are very few groups collecting this type of data. It's an exciting target for new research into embodied intelligence."

As environments like factories, labs and hospitals continue opening up to human-robot collaboration, Kim believes tactile force sensing will grow increasingly vital. The 3D printed skins offer an affordable, scalable way to endow robots with this safety-enhancing and interaction-enriching capability.

"Tactile inputs are a relatively unexplored frontier in robotics," said Kim. "We hope techniques like ours inspire more work collecting valuable force data to make human-robot interactions richer and more seamless."

The team's novel manufacturing approach brings the dream of softer, safer, more perceptive robots one step closer by giving them a gentle sense of touch in lightweight, flexible form. With artificial skins rolled off affordable 3D printers, a new era of human-robot cooperation could be within grasp.