I am trying to build 8x8 grid that consists of capacitive sensors which we have successfully made by using a high resistors and copper sheets. I used Arduino's library to control it, but my problem is how to control all 64 of them. I have access to almost every kinds of Arduinos in my schools's interaction lab, and since Mega has lots of digital pins that I can use, I have chosen that. However even it has 53 digital pins, and I need to use 10 more pins for other components of my project. I have a multiplexer but sensors I have built and multiplexer do not work together. The problem is, in the library from Arduino, in order to control the capacitive sensor, I need to specify its send and receive pins clearly. If I detach the sensor from on-board pins and attach it to mulplexed pins, it no longer has a PIN number to give to the library. I tried to hack the library, but it was a dead end. Does this means that I cannot use multiplexer and capacitive sensors together, or am I missing something?

Any solution to multiplexing problem or any alternatives that I can use instead of 64 capacitive sensors would be greatly appreciated.