Human skin allows for interfacing with external physical environments through numerous receptors interconnected with the nervous system. Scientists have been trying to transfer these features to artificial skin, aiming at robotic applications. Operation of robotic systems heavily relies on electronic and magnetic field sensing functionalities required for positioning and orientation in space.
Recent advancements in flexible sensors and organic electronics provided important prerequisites. These devices can operate on soft and elastic surfaces, whereas sensors perceive various physical properties and transmit them via readout circuits. To closely replicate natural skin, however, it is necessary to interconnect a large number of individual sensors. This challenging task became a major obstacle in realizing electronic skin.
Early demonstrations were based on an array of individual sensors addressed separately, which resulted in a tremendous number of electronic connections. In order to reduce the necessary wiring, complex electronic circuits — such as shift registers, amplifiers, current sources, and switches — had to be combined with individual magnetic sensors to achieve fully integrated devices.
Researchers overcame this obstacle by developing an active matrix magnetic sensor system that consists of a 2 × 4 array of magnetic sensors, an organic bootstrap shift register for controlling the sensor matrix, and organic signal amplifiers. All electronic components are based on organic thin-film transistors and are integrated within a single platform. The system has a high magnetic sensitivity and can acquire the two-dimensional magnetic field distribution in real time. It is also very robust against mechanical deformation such as bending, creasing, or kinking. In addition to full system integration, the use of organic bootstrap shift registers is a very important development step towards active matrix electronic skin for robotic and wearable applications.
The integrated magnetic functionalities prove that thin-film flexible magnetic sensors can be integrated within complex organic circuits. The ultra-compliant and flexible nature of these devices is an indispensable feature for modern and future applications such as soft robotics, implants, and prosthetics. The next step is to increase the number of sensors per surface area as well as to expand the electronic skin to fit larger surfaces.