Magnetic e-skins usher in new era in sensor engineering

Up until now, to manipulate virtual objects, you needed equipment that relied on the optical detection of moving body parts. However, this equipment usually included cameras, whose resolution is not good enough to reconstruct fine movements of the body, and goggles and gloves, which are bulky and restrictive. With these issues in mind, EU-funded researchers set out to develop versatile sensing devices that interacted with magnetic fields.

In the initial stages of the project, researchers knew that to achieve touchless manipulation of virtual objects, they needed to combine two key functions in a single gadget. These were the ability to detect nearby objects and direction in space. Yet, although the team’s early wearable electronics successfully achieved the first function using magnetic field sensors, it wasn’t able to analyse spatial directions.

Now the SMART researchers have overcome this barrier and developed the first ultrathin e-skins capable of tracking body movements.

e-skin device tracks body movements for first time

The e-skin is essentially a two-dimensional magnetic field sensor attached to ultrathin polyimide foils. Only 3.5 micrometres thick, this stretchable, bendable and printable device can easily be applied to any part of your hand and is practically unnoticeable to the wearer. It can also be integrated with soft and shapeable materials, such as textiles for wearable electronics. What is more, it can withstand temperatures up to 344 °C, which is its breaking point. This is especially remarkable when compared with commercial polymers such as Mylar and the much thicker PET and PEEK, all of which break at less than half this temperature.

The latest accomplishment of the SMART project was presented in a recent paper published in the journal ‘Science Advances’. Researchers describe how, by interacting with a magnetic field, their device is able to move virtual objects that aren’t in their direct line of sight without touching them.

Researchers demonstrated this concept by mounting the 2D sensor on an elastic wristband to create a virtual keypad. A permanent magnet attached to a person’s fingertip provided the magnetic input. When the fingertip approached the wristband at a certain encoded angle (e.g. 90 °), the sensor converted the magnet’s position into a predefined character (e.g. the number four).

They also showed how a virtual light bulb can be dimmed by touchless manipulation, and relying solely on the interaction with magnetic fields. Here, the e-skin was attached to the palm of the hand. The wearer controlled the light by moving their hand near a permanent magnet acting as a virtual dial. Angles between 0 ° and 180 ° were encoded to correspond to the typical movements a hand makes when operating a real dial. Rotating the hand above the virtual dial just a few degrees to the left or right either dimmed or brightened the virtual light bulb, respectively.

Team members believe that this technology will open the way for a wide range of applications not only in sports and gaming, but also in regenerative medicine and the security industry. It’s further predicted that additional improvements to flexible sensors will make e-skin interaction with the Earth’s magnetic field a real possibility in the future.

The SMART (Shapeable Magnetoelectronics in Research and Technology) project, which ended last year, aimed to give the EU an advantage in the development of a unique class of devices with important functionality. Fast and flexible, these materials were also designed to react and respond to a magnetic field.

For more information, please see:
SMaRT website
Article published in the journal Science Advances