Do touchscreen gloves work

Why can't touch screens be operated with gloves?

Operating touchscreens can be a challenge in winter. Why is it that cell phones and the like cannot be operated with gloves, but can be operated with a pickle?

Just a few years ago, most of us would have seemed like magic, which is a matter of course today: You tap a point on the glass of a smartphone or tablet computer to enter a letter, for example. Or wipe it with your finger so that a new image suddenly appears. Or spread two fingers - and the view enlarges as if by magic. The touch-sensitive screen has revolutionized the operation of these devices (or even made it possible in the first place). But how can a rigid glass or plastic pane react so sensitively to contact? It neither conducts electricity nor is it deformed by the pressure of the finger; neither sensors nor switches nor electrical contacts can be seen on their surface. And why does the technology fail in almost all models when you want to operate them with a glove in the cold? Under normal circumstances, so-called “capacitive touchscreens” are able to determine the position of a finger extremely precisely. Their technology is based on a network of hundreds of detectors that are located directly under the pane of glass. They consist of layers of indium tin oxide that are just a few millionths of a millimeter thick - a material that can conduct electricity and is still transparent.

How science explains everyday life to us

Every child, but also many adults, ask themselves similar questions when looking at the world around them: Why does hot air rise, why does the brook ripple, why can you see your breath on cold days, and why does it flash during a thunderstorm? The GEOkompakt edition "Why is the sky blue? How science explains everyday life" provides answers to 50 such questions.

Each of these tiny detectors has a simple but important property: they can store a certain number of electrical charges. Complicated control electronics determine how many electrical charges enter the storage unit. To do this, it charges each individual detector 400 times per second via extremely fine lines, discharges them again and counts the charges in the process. It gets interesting when a finger is on the pane of glass. Because around the charged detector (following Coulomb's law, a universal physical principle) an electrical field has formed that penetrates the glass pane of the touchscreen - and even extends into the finger on it. Something amazing is happening there: Because there are easily movable electrically charged particles in human tissue, they are coupled to the charges in the detector via the electric field. This makes them part of the charge storage system - its capacity changes. And this is exactly what the control electronics register. It recognizes that the memory capacity of the detectors has changed at a certain point on the display and reports: “There is a finger here.” All of this happens extremely quickly.

Touchscreens can be operated with cucumbers, bananas and sausages

However, there are problems with gloves. Because they are usually made of insulating materials such as wool or fleece. The electrical charges are firmly in place in it. So they cannot be moved as easily as with the finger and cannot change the capacity of the charge storage in the touchscreen. In principle, the electric field can even penetrate a glove - but the finger is then further away from the pane of glass and the effect is too small to be recognized. That could change soon, however, because engineers recently presented a touchscreen whose sophisticated electronics can reliably recognize the signals from a finger in the glove. Touchscreens, on the other hand, can be operated surprisingly well with a cucumber, a banana, a carrot and even a sausage: All these foods differ amazingly little from a human finger in terms of the mobility of their electrical charges.

#Subjects