To understand how a stylus works, we first need to explain how a touchscreen works.
There are five types of touch-screen technology: resistive, surface capacitive, surface acoustic wave (SAW), infrared (IR), and projected capacitive. The commonly used types are resistive and surface capacitive touchscreens.
The resistive touchscreen has two thin metallic layers separated by a small gap. When the user presses on the touchscreen, the two metallic layers establish a connection resulting in an electrical flow.
The surface capacitive touchscreen has an electrode layer on the top of the touchscreen that reacts to the static electrical capacity of the human body when pressed. Such touchscreens require passive stylus pens. We’ll get to them in a bit.
A touch-screen pen needs to be capable of transmitting an electrical charge to replace your input on surface capacitive touchscreens. The same pen interacts with a resistive touchscreen without any issues. Resistive touchscreens don’t require anything except the pressure to activate them. Therefore, anything can be a stylus if it doesn’t damage the device.