Soft e-skin utilizes magnetic fields to independently sense three-axis forces

Electronic skins (e-skins) are flexible sensing materials designed to mimic the human skin’s ability to pick up tactile information when touching objects and surfaces. Highly performing e-skins could be used to enhance the capabilities of robots, to create new haptic interfaces and to develop more advanced prosthetics.

In recent years, researchers and engineers have been trying to develop e-skins with individual tactile units (i.e., taxels) that can accurately sense both normal (i.e., perpendicular) and shear (i.e., lateral) forces. While some of these attempts were successful, most existing multi-axis sensors are based on intricate designs or require complex fabrication and calibration processes, which limits their widespread deployment.

Researchers at CNRS-University of Montpellier have introduced a new soft e-skin that leverages magnetic fields to independently detect forces on three axes. This e-skin, described in a paper published in Nature Machine Intelligence, has a simple design that could be easy to reproduce on a large scale.

“Tactile sensing is important for both humans and robots to perceive and interact physically with the world, while the existing artificial tactile sensors are still limited in many aspects,” Youcan Yan, first author of the paper, told Tech Xplore.

“Inspired by human skin and the self-decoupling property of the Halbach array, this research aimed at developing a tactile sensing technology that can decouple 3D forces in a simple sensor structure and calibration process.”

The sensor developed by Yan and his colleagues consists of three main layers. The top layer is a flexible magnetic film, the middle one an elastomer sheet and the bottom one a printed circuit board (PCB).

When an object or surface touches the sensor, the top flexible magnetic film deforms. This deformation in turn affects the magnetic field beneath it, allowing the PCB-based bottom layer to pick up changes caused by contact with a given object/surface.

“Such a variation in the magnetic field is detected by the Hall sensors on the bottom layer, which can be then used to estimate the applied force,” explained Yan.

“Compared with non-self-decoupling sensors that are complex in either sensor structure or calibration process, our sensor reduces calibration times from cubic (N³) scales to linear (3N) scales, thus enabling streamlined design and easy calibration that are important for practical applications.”

Yan and his colleagues evaluated their sensor in a series of preliminary tests and found that it could measure the three-dimensional distribution of forces applied to it.

The researchers showed that it could be used to measure the distribution of forces on artificial knee joints, to teach robots new manual skills via touch-based demonstrations and to monitor biological signals while users are engaged in different activities.

“We found that the 2D self-decoupling property of the Halbach array can be generalized to 3D by overlaying two sinusoidally magnetized flexible magnetic films with orthogonal magnetization patterns,” said Yan.

“This provides the foundation for the sensor design, and we demonstrate that our sensor can facilitate a diverse range of applications, including measuring the three-dimensional force distribution in artificial knee joints, teaching robots to make coffee by touch demonstration, and monitoring the interaction forces between knee braces and human skin during various activities.”

The sensor developed by this team of researchers could soon be improved further and tested in a wider range of scenarios. In the future, it could be integrated with existing or newly developed robotic systems, wearable technologies and prosthetics to improve their tactile sensing capabilities.

“We will now further optimize the sensor design, for instance by changing the materials it is made of and integrate it with other types of robots such as humanoids,” added Yan.

© 2024 Science X Network