how does a phone stylus work?

813 views

How does a phone stylus still register on a screen when something like an eraser, which feels somewhat similar, doesn’t?

What allows some materials to register on a screen, and others not to register?

In: Technology

2 Answers

Anonymous 0 Comments

Most touch screens these days relying on the finger modifying the amount of electrical current that moves across the surface of the screen. The stylus does the same thing.

Some materials simply don’t disrupt the current enough to register as a “touch”.

Anonymous 0 Comments

Touch screens generally work due to “capacitance”. That is the ability for a material/object to store an electrical charge.

The human body is reasonably good at this, due mainly to containing a large amount of water. Water molecules are [slightly more positive on one end and more negative on the other.](https://s3.amazonaws.com/user-content.enotes.com/e9051bff4b4e7a03460d69f59ac430160eb764f6.png) If you expose them to an electrical field (a voltage), the water molecule will rotate a bit. In this way, it’s storing a bit of energy. If you remove the voltage, it will go back to moving around more freely.

Touch screens work by putting a tiny voltage on the screen (in many places, one after the other, very rapidly) and detecting if there’s a tiny current flow. If there is, something with capacitance has touched or come near the screen. Like a human finger.

But it doesn’t have to be the finger itself, it can be something electrically well connected to that finger. That will form a conductive path to the finger and it’s almost as good.

And that’s what a phone stylus does. It is conductive, and it therefore provides a “virtual finger” that increases the capacitance at the screen where it touches.

If a material is not very conductive, or not in electrical contact with something with high capacitance, it won’t register on the screen.