Nearly all touch screens on phones are capacitive touch. These screens detect touch by a change in capacitance.
There are several examples online of people taping a wire to the screen and then switching a relay to simulate a touch.
I've verified a relay works. However, I was hoping I could switch to using a transistor or ideally just an IO line. I tried a quick test with Arduino by switching an IO line between high impedance and 0V. This didn't work. I suspect it's because of the parasitic capacitances you find in integrated circuits.
I'm wondering if you guys know of a solid state device/transistor that has exceptionally low capacitance between the source/drain that I could try?