What can I use a mobile phone camera instead of a finger?

At present, touch screens are basically capacitive screens, and capacitance pen can directly touch the screen instead of fingers.

Capacitive touch screen works by current induction of human body. It's a four-layer composite glass screen. The inner surface and interlayer of the glass screen are coated with a layer of ITO (namely coated conductive glass), and the outermost layer is a thin protective layer of Shi Ying glass.

In the induction of capacitive screen, as long as there is a weak current, it can be sensed by the screen, so anything with conductivity and slight current can control the capacitive screen.