Sensor-driven "skin" possible with web of circuits, organic signal amplifiers

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February 24, 2020

Research that could be a game-changer for troops in the field is currently being undertaken by several teams attempting to replicate human skin.

Imagine this scenario: A group of warfighters enters a hazardous, communications-denied area just as the weather turns ugly and the opposition remains invisible. Having no access to reliable communications with their base, the troops run the real risk of frostbite, lack of supplies, and injury.

Let’s rerun this situation differently: Flexible sensors worn by the service members – imperceptible devices with multiple sensors that perceive various physical properties and transmit them via readout circuits – “read” the conditions; send the data back to a secure base; and dispatch vital gear, food, and other supplies via small unmanned aircraft systems (UASs) or drone.

The second situation is now very plausible and could happen in the near future, according to new research from scientists in Dresden and Chemnitz (Germany) and Osaka (Japan). A recent article published in Science Advances has presented what the team calls a “pioneering active matrix magnetic sensor system.” As described in the journal article, the sensor system consists of a 2 x 4 array of magnetic sensors, an organic bootstrap shift register required for controlling the sensor matrix, and organic signal amplifiers, all based on organic thin-film transistors and integrated within a single platform.

The sensor system’s ability to work at low supply voltages below 4 volts plus its high-frequency operation at approximately 100 Hz make it the most imperceptible and functional design to date, the researchers say. The authors assert that their findings can pave the way for the development of a new generation of flexible electronics to be used in applications such as electronic skins (known as e-skins), soft robotics, and biometric devices.

The study lays out the active magnetosensory matrix (MSM) system’s high level of magnetic sensitivity and details its tested robustness in trials of mechanical deformation such as bending, creasing, or kinking. In addition to full system integration, the researchers say that the use of organic bootstrap shift registers – a bootstrap circuit is one where part of the output of an amplifier stage is applied to the input for use at startup – marks an important step toward active-matrix electronic skin for robotic and wearable applications.

The components used by the study team were fabricated on the same imperceptible platform. The researchers’ use of an ultrathin polymer substrate and encapsulation enabled testers to wear the magnetosensitive electronic membrane. The study detailed that the organic field-effect transistors and the magnetic sensors are folded and/or bent around a thin copper wire without affecting the electric performance. (Figure 1.)

Figure 1 | Flexible electronic skin equipped with an array of sensors and complex electronic circuits – all designed and developed as a magnetosensory matrix. Photo courtesy Masaya Kondo, Institute of Scientific and Industrial Research, Graduate School of Engineering, Osaka University, Japan.

Prof. Dr. Oliver G. Schmidt, director at the Leibniz Institute for Solid State and Materials Research Dresden, stated regarding the study: “Our first integrated magnetic functionalities prove that thin-film flexible magnetic sensors can be integrated within complex organic circuits. The ultracompliant 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.”

Other similar studies and trials of wearable flexible electronics sensors are also ongoing in the U.S., with one such study between the Air Force Research Laboratory (AFRL) and government/industry/academic consortium Nextflex that seeks to advance wearable remote human-performance monitoring technologies to benefit both the warfighter and consumer. The AFRL study is considering testing a small-scale production run of devices; if successful, says AFRL scientist and program manager Dr. Jeremy Ward, this technology will hold huge benefits for war­fighters: “This approach to reliably sensing the biochemistry of a human has the potential to be transformative.”