Capacitive touch under silicone near LED array?

[clem]

I'm working on a project that need a simple touch interface. Minimally a single touch, but I'd prefer to be able to detect a left swipe, right swipe and a tap.

The design has a silicone overmold, a plastic support frame and a rigid-flex PCB. The rigid-flex PCB has a discrete LED display and the touch sensing region needs to be above the LED display. I had hoped to rely on an accelerometer to provide tap/tilt user input, but a touch interface would be preferred.

There isn't much room between the LEDs to put capacitive touch interface between the pixels. One thought is to put an ITO/PET film above the display, so the stack would be silicone overmold, PET film, flex PCB, plastic mechanical support. It appears that the dielectric is suitable for capacitive touch, so that shouldn't be a problem.

The big issue is trying to put a capacitive sensors in close proximity to the LEDs. I'm driving the LEDs using several AMS AS1130 crossplex LED drivers. This driver sinks one of its outputs and then sources or floats the other 11. It relies on being able to reverse bias the LEDs to get 12*11 LEDs with only 12 pins. As the LEDs are PWMed they will be changing capacitance which is an issue for the touch controller. An atmel app note http://www.atmel.com/Images/doc10752.pdf says that you can bypass the LEDs with ~1nF to provide a low impedance path as seen by the sensor. Adding a small bypass cap on each of the driver outputs would be reasonable, but it is unclear to me if this is sufficient.

Another option is a resitive touch interface, but I'd rather avoid having to pull gestures from x,y data and I'd assume that the restive touchscreen would be more expensive.

Any ideas on how best to tackle this problem? Has anyone tried something like this?