Numerical Simulation of Mutual Capacitance Touch Screens for Ungrounded Objects

Mutual capacitance touch screens translate billions of finger touches to digital signals around the world daily. By enabling these screens to detect ungrounded objects, it may be possible to extend their functionality by detecting tangible user interface objects on the screen surface. This paper presents results from finite-element method simulations, as well as experiments, showing that the mutual capacitance touch screen panel sensing principle can be used to detect ungrounded objects. Looking into how different design parameters of the touch panel affect grounded and ungrounded touch differently, we have found a film-glass-film stack-up to be 1.55 times more sensitive to ungrounded than grounded touch, compared with 0.65 and 0.20 for two different configurations of glass-film stack-up.