What makes a Rubber TouchScreen friendly?

Hi everyone,

i'm part of a small project at my university and we just can't find out what characteristic/property of an thermoplastic elastomehr used for all the stylus' makes them useable for a touchscreen.

We tried a whole lot of different rubbers/elastomehrs and a few triggered the touch-sensors on smartphone screens and a few didn't.

We simply need to know what exactly makes it "capacitive" (i don't even know if thats a word in english) / touch-Screen-usable.

Sadly, uncle google didn't bring it.

Thanks in advance and have a nice weekend