image: Conceptual overview of the vision-based ProTac sensing technology. ProTac can actively switch between proximity and tactile sensing modes, relying on input images captured by inner cameras and a soft functional skin with controllable transparency.
Credit: Van Anh Ho from JAIST.
Ishikawa, Japan -- Robots are becoming increasingly integrated into everyday environments—from homes and hospitals to factories and farms. However, safely operating around humans requires more than strength or speed. Robots must also sense their surroundings, detect physical contact, and respond quickly. Conventional sensors, especially those embedded in soft materials, often fall short when it comes to real-time, large-area tactile and proximity sensing.
To address this challenge, a research team led by Professor Van Anh Ho and Dr. Quan Khanh Luu from Japan Advanced Institute of Science and Technology (JAIST), Japan, developed ProTac, a novel vision-based soft sensing skin for robots. The study was published in the journal IEEE Transactions on Robotics on July 28, 2025, and presents a scalable approach to multimodal robotic perception.
At the core of ProTac is a polymer-dispersed liquid crystal (PDLC) layer that can switch between transparent and opaque states when voltage is applied. When transparent, embedded cameras can “see” through the skin to detect nearby objects. When opaque, those same cameras track how the skin deforms, allowing the robot to sense touch, pressure, and the location of contact. This dual-mode sensing enables real-time environmental perception using a single soft layer, eliminating the need for complex embedded electronics.
“This innovation with sensor design simplicity allows robots to perceive both contact and nearby obstacles across a large-area skin in real time, which is difficult to achieve with conventional electronic skins,” Prof. Ho explained.
To validate the design, the team developed a prototype called the ProTac link, a cylindrical robot arm segment wrapped in a soft sensing skin and equipped with stereo cameras at both ends. This prototype can detect approaching objects from multiple angles, estimate distance, and recognise multiple touch points with high accuracy. It also supports adaptive behaviors such as proximity-based speed adjustment and reflexive contact avoidance.
“ProTac can be applied to dexterous robotic manipulation in various domains where safety and delicate physical interaction are critical,” says Dr. Luu.
The researchers envision broad applications across collaborative robotics, assistive devices, and soft robotic systems in agriculture or domestic care. In factories, ProTac-equipped robots could slow or stop when a human worker approaches. In elder care, service robots could provide physical assistance while maintaining safe, responsive contact. In the long term, ProTac could contribute to the development of full-body sensing systems for humanoid robots.
“In the long term, this research lays the groundwork for intelligent general-purpose humanoid robots equipped with full-body multimodal soft sensing skins, especially those with a sense of touch,” said Dr. Ho.
Alongside the skin, the team developed learning algorithms and control strategies that convert sensor data into robotic actions, enabling responsive and autonomous behavior in dynamic environments. Designed with simplicity, modularity, and scalability in mind, the ProTac system can be integrated into both new and existing robotic platforms.
To accelerate progress in the field, the researchers have made their design files, models, and software open source. By combining mechanical simplicity with multimodal perception, ProTac brings robots a step closer to understanding—and safely interacting with—the complex, tactile world around them.
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About Japan Advanced Institute of Science and Technology, Japan
Founded in 1990 in Ishikawa prefecture, the Japan Advanced Institute of Science and Technology (JAIST) was the first independent national graduate university that has its own campus in Japan. Now, after 30 years of steady progress, JAIST has become one of Japan’s top-ranking universities. JAIST strives to foster capable leaders with a state-of-the-art education system where diversity is key; about 40% of its alumni are international students. The university has a unique style of graduate education based on a carefully designed coursework-oriented curriculum to ensure that its students have a solid foundation on which to carry out cutting-edge research. JAIST also works closely both with local and overseas communities by promoting industry–academia collaborative research.
About Professor Van Anh Ho from Japan Advanced Institute of Science and Technology, Japan
Prof. Van Anh Ho is a Senior Member of IEEE and Associate Professor at the Japan Advanced Institute of Science and Technology (JAIST), where he leads a lab on soft robotics. He previously worked as a research scientist at Mitsubishi Electric Corporation and Assistant Professor at Ryukoku University. He earned his Ph.D. in Robotics from Ritsumeikan University in 2012. His research covers soft robotics, tactile sensing, haptics, and bio-inspired systems. Dr. Ho has received numerous honors, including the JSPS Fellowship, IEEE Young Researcher Award, and Best Paper Finalist nominations.
Funding information
This work was supported in part by the JSPS Grant-in-Aid for Scientific Research (KAKENHI) under Grant 24KJ1203 and in part by the JST Precursory Research for Embryonic Science and Technology PRESTO under Grant JPMJPR2038.
Journal
IEEE Transactions on Robotics
Article Title
Vision-based Proximity and Tactile Sensing for Robot Arms: Design, Perception, and Control
Article Publication Date
28-Jul-2025