Artificial hairs provide added sensitivity to e-skin

Medical sensors or artificial skin for humanoid robots could become more sensitive with a new e-skin integrated with artificial hairs.

Highly integrated flexible microelectronic 3D sensorics perceive movement of fine hairs on artificial skin
Highly integrated flexible microelectronic 3D sensorics perceive movement of fine hairs on artificial skin - (Credit: Research Group Prof. Dr. Oliver G. Schmidt)

Surface hairs perceive and anticipate the tactile sensation on human skin and even recognise the direction of touch, but modern electronic skin systems lack this capability and cannot gather this information about their vicinity.

Now, a research team led by Prof. Dr. Oliver G. Schmidt, head of the Professorship of Material Systems for Nanoelectronics and Scientific Director of the Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN) at Chemnitz University of Technology, Germany, has adopted a new approach to the development of extremely sensitive and direction-dependent 3D magnetic field sensors that can be integrated into an e-skin system (active matrix). The team’s findings are reported in Nature Communications.

In a statement, Christian Becker, a PhD student at MAIN and first author of the study said: "Our approach allows a precise spatial arrangement of functional sensor elements in 3D that can be mass-produced in a parallel manufacturing process. Such sensor systems are extremely difficult to generate by established microelectronic fabrication methods."

The core of the system is a anisotropic magnetoresistance (AMR) sensor, which can be used to precisely determine changes in magnetic fields. Current applications for AMR sensors include speed sensors in cars or determining the position and angle of moving components in machinery.

To develop the highly compact sensor system, the researchers took advantage of the so-called "micro-origami process". This process is used to fold AMR sensor components into three-dimensional architectures that can resolve the magnetic vector field in three dimensions.

According to the team, including researchers from IFW Dresden, micro-origami allows many microelectronic components to fit into small space and arrange them in a geometry that is not achievable by any conventional microfabrication technologies.

"Micro-origami processes were developed more than 20 years ago, and it is wonderful to see how the full potential of this elegant technology can now be exploited for novel microelectronic applications," said Prof. Schmidt.

The research team integrated the 3D micro-origami magnetic sensor array into a single active matrix, where each individual sensor can be addressed and read-out by microelectronic circuitry.

"The combination of active-matrix magnetic sensors with self-assembling micro-origami architectures is a completely new approach to miniaturise and integrate high-resolution 3D sensing systems," said Dr. Daniil Karnaushenko, who contributed to the concept, design and implementation of the project.

The research team said it has succeeded in integrating the 3D magnetic field sensors with magnetically rooted fine hairs into an artificial e-skin, which is made of an elastomeric material into which the electronics and sensors are embedded.

As with human skin, each hair on an e-skin becomes a full sensor unit that can perceive and detect changes in the vicinity, so the magneto-mechanical coupling between 3D magnetic sensor and magnetic hair root - in real-time - provides a new type of touch-sensitive perception by an e-skin system. According to the team, this could be a particularly useful safety feature in future human-robot interaction.