On a compass only a few thousandths of a millimetre thick, the scientists applied electronic magnetic sensors capable of detecting the smallest geomagnetic fields. The sensor is extremely sensitive – it registers magnetic fields in the order of 40 to 60 microtesla. This corresponds approximately to the strength of the earth’s magnetic field.
The sensor enabled the scientists to show for the first time that the natural geomagnetic field is sufficient to control virtual objects without contact. This makes it possible to digitize these movements and transfer them into the virtual world – for example in the field of gesture control.
The principle behind the sensors, which consist of wafer-thin strips of the metal permalloy, is based on the so-called anisotropic magnetoresistive effect. “This means that, depending on the orientation to an external magnetic field, the electrical resistance of these layers changes,” explains Gilbert Santiago Canón Bermúdez, first author of the report. In order to align the sensors with the earth’s magnetic field, the scientists coated the ferromagnetic strips at an angle of 45 degrees with a conductive material, in this case gold platelets. The current can therefore only flow at this angle, making the sensors most sensitive in the vicinity of particularly small magnetic fields. “So the voltage is strongest when the sensors are pointing north and weakest when they are pointing south,” explains Canón Bermudéz.
In outdoor experiments, the researchers were able to prove that their configuration works. A test person glued the sensor to his index finger oriented himself from north to west to south and back – which led to the electrical voltage falling or rising accordingly. The points of the compass shown in this way corresponded to an ordinary compass used for comparison.
This was the first time the HZDR scientists had developed a portable sensor that could reproduce the functionality of a normal compass and give people an artificial sense of magnets. The physicists also succeeded in transferring the principle into virtual reality. Here, with software for the production of computer games, they were able to control a character using their magnetic sensors alone.
Since the sensors can withstand severe bending and curvature without losing functionality, the researchers see great potential for their development – not just as access to virtual reality. “This would make it possible, for example, to examine the effects of a magnetic sense on humans more closely without having to resort to cumbersome experimental installations that often distort the results,” says Gilbert Santiago Cañón Bermúdez. This “electronic skin” could not only help with orientation problems, but also simplify access to virtual reality.
Further information: https://www.hzdr.de/db/Cms?pNid=0