Magnet sensors: The navigation finger

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Before long, you will not need any type of map to find your way. That’s because an electronic skin will reliably point the way to the north and provide seamless access to virtual realities.

The things that we perceive about the environment are less than half of reality anyway. To begin with, our senses are limited. Other types of senses do not even exist at all. A quick visit to the animal kingdom demonstrates just how inadequate our senses are. Bats hear ultrasonic sounds. Hammer-head sharks “feel” electric fields, and some species of otters can use their pit organ to create a three-dimensional thermal image of their surroundings. And the list goes on and on. Humans can acquire such abilities only through technical efforts that can sometimes be quite elaborate. This includes things like the ability of birds to use the Earth’s magnetic field to find their way.

Researchers at the Helmholtz Center Dresden-Rossendorf (HZDR) have developed highly sensitive, magnetic field sensors that can determine the movement of a body in a room through interactions with the Earth’s magnet field. The sensor is razor-thin and flexible — qualities that enable it to be placed anywhere on the skin. The researchers decided to place the sensor on the index finger. When a test subject moves from the north to the west and then the south before heading back to the north, the voltage rises or falls accordingly. This is essentially the same process used in a normal compass.

Virtual trips with magnet sensors

Magnetic sensors
When the hand swipes left, towards the magnetic north, the animal also moves in that direction (a). A swipe to the right, makes it go the opposite way (b). When the hand moves towards the middle, the panda moves back slightly towards the left (c). (Image: HZDR/Cañón Bermúdez).

But this is just one side of the magnetic coin. The principle turns up in virtual realities as well. With Panda3D, a software used to produce computer games, researchers were able to control a digital panda using only magnet sensors. The north represents a movement to the left and the south to the right, for example. Detection of the magnetic field from the real world can be directly transferred to the virtual one.

The sensors are made of ultra-thin strips of a metal called permalloy. The principle behind it – anisotropic (depending on the room direction) magnetoresistance (AMR) – has been known for about 60 years. It occurs in materials that have their own magnetic properties. The electric resistance of these layers varies according to their orientation in relation to an outer magnetic field. To aim them at the Earth’s magnetic field, researchers coated these ferromagnetic strips with a conductive gold plate arranged at a 45-degree angle. For this reason, electricity can flow only in this angle. The sensors are most sensitive when they are near particularly small magnet fields. The voltage is strongest when the sensors are pointed to the north and weakest when they are pointed to the south.

As a contact-less interaction platform between humans and machines that is placed on the skin, the magnetic field sensors open up a range of other uses, including soft robotics and functional medical implants.




Magnet sensors (Image: pixabay).

An electronic skin with magnetosensitive capabilities create a bionic analog of a compass. (Image: pixabay).