Robots that work alongside humans need two different sensing abilities. They must detect people approaching from a distance to avoid collisions, and they must also sense extremely light touch when handling delicate objects.
Traditionally, engineers have struggled to combine these capabilities in a single sensor.
Small electrodes provide high-resolution tactile sensing but can only detect objects at very short distances. Larger electrodes can sense farther away but lack the precision needed for delicate manipulation.
This trade-off has limited the design of electronic skins used in collaborative robots.
Researchers at South China University of Technology say they have overcome this limitation with a new flexible capacitive sensor array that can dynamically change how it senses its surroundings.
The system allows a robot to detect distant objects and still maintain precise tactile sensitivity when contact occurs.
The design introduces a dynamic shielding layer above an array of electrodes.
By adjusting how the electrodes are electrically connected and masked, the system can shift between long-range proximity sensing and detailed touch sensing without changing the physical size of the electrodes.
Inspired by human vision
The researchers say the idea came from how the human eye adjusts to different viewing conditions.
“When we focus on a book, our pupils contract to sharpen the fine details. When we look at a dark and distant road, it dilates to gather more light. We applied this exact logic to electric fields.” Dr. Xie explained.
When the shielding layer narrows the sensing area, the system focuses on individual sensing units, allowing the robot to detect fine tactile details.
This mode is useful when the robot must grasp delicate parts or identify the edges of small objects.
When the shielding expands the sensing area, the electrodes project an electric field farther into the surrounding space. This allows the robot to detect approaching objects before contact occurs.
According to the team, this architecture more than doubled the maximum detection depth compared with traditional dual-mode sensors. The researchers reported a 104.56 percent increase in sensing range.
Long-range sensing, fine touch
In tests, the sensor detected approaching objects from more than 90 mm away. That distance may seem small, but it is enough to allow a robotic arm to stop before colliding with a human worker in a busy environment.
Once contact occurs, the sensor can detect extremely light touch while also tolerating high pressure. The system can register forces of just a few grams and withstand pressures of up to 400 kPa.
Such capabilities could make robotic systems safer and more versatile in factories or other shared environments where machines interact directly with people.
However, the researchers say scaling the technology for real-world deployment will require further work.
To achieve high sensitivity, the team used a sacrificial template method to create microscopic pores in the sensor materials. This process produces sponge-like structures that can vary between individual sensor units.
In prototype tests, the researchers reported performance variation between sensors of about 6.3 percent to 6.8 percent.
Another challenge is environmental interference. Capacitive sensors are sensitive to electromagnetic noise, temperature shifts, and humidity changes. Industrial settings with heavy machinery could create electrical noise that affects sensor readings.
The researchers say future systems may require improved shielding or machine learning algorithms that can filter interference and maintain reliable sensing.
If these challenges are addressed, the technology could help simplify robotic perception.
Instead of combining multiple sensing systems, robots may eventually rely on a single adaptive electronic skin that detects nearby objects and senses physical contact with high precision.
The findings were published in the journal International Journal of Extreme Manufacturing.