Soft robotic skins with touch sensors have emerged as a promising feature for robots that are both safer and more intuitive for human interaction, revolutionizing human-robot interaction. However, practical limitations like manufacturing challenges and cost inefficiency have hindered their widespread use.
A recent study by the University of Illinois Urbana-Champaign demonstrated that the efficient manufacturing of soft skin pads doubling as sensors from thermoplastic urethane using 3D printers is a game-changer.
“Robotic hardware can involve large forces and torques, so it needs to be made quite safe if it’s going to either directly interact with humans or be used in human environments,” said project lead Joohyung Kim, a professor of electrical & computer engineering at the University of Illinois Urbana-Champaign. “It’s expected that soft skin will play an important role in this regard since it can be used for both mechanical safety compliance and tactile sensing.”
The 3D-printed pads offer a groundbreaking solution as they serve as both flexible skins for a robotic arm and pressure-based mechanical sensors. These pads feature airtight seals and connect to pressure sensors, functioning much like a squeezed balloon. They deform upon contact and activate the pressure sensor through displaced air.
Kim emphasized the cost-effectiveness and versatility of this innovation, stating, “Tactile robotic sensors usually contain very complicated arrays of electronics and are quite expensive, but we have shown that functional, durable alternatives can be made very cheaply. Moreover, since it’s just a question of reprogramming a 3D printer, the same technique can be easily customized to different robotic systems.”
Demonstrating practical applications, the researchers highlighted safety, illustrating how the pads can automatically halt the arm’s movement upon detecting proximity to hazardous areas such as joints. Additionally, these pads enable operational capabilities, allowing the robot to interpret touches and taps as instructions.
The versatility and cost-effectiveness of 3D-printed parts make them ideal for adapting to new robotic systems and replacing old ones. This is especially valuable in situations where cleaning and maintaining parts is expensive or impractical.
For instance, in a hospital setting, soft-skinned robots would require regular sanitization or replacement of their skin, incurring significant expenses. However, with 3D printing, interchangeable parts can be produced inexpensively and easily attached to the robot body.
The incorporation of tactile inputs through these new pads represents a relatively unexplored dimension of robotic sensing and control. It is hoped that the simplicity of this new manufacturing technique will generate increased interest in this field.
“Right now, computer vision and language models are the two major ways that humans can interact with robotic systems, but there is a need for more data on physical interactions, or ‘force-level’ data,” he said. “From the robot’s point of view, this information is the most direct interaction with its environment, but there are very few users – mostly researchers – who think about this. Collecting this force-level data is a target task for me and my group.“
Journal reference:
- Kyungseo Park, Kazuki Shin, Sankalp Yamsani, Kevin Gim, Joohyung Kim. Low-Cost and Easy-to-Build Soft Robotic Skin for Safe and Contact-Rich Human–Robot Collaboration. IEEE Transactions on Robotics, 2024; DOI: 10.1109/TRO.2024.3378174
