Unity QCAR Integration 3d model user interaction

I’ve been doing some experiments with QCAR and Unity so far I’ve been able to display a 3d model using an ImageTarget. My 3d model is a car, composed of several meshes, one of them represents the left door. I would like to know how to detect when the user “touches” the door?

I’m assuming this is somehow possible, but don’t know how to make it happen?

Thanks in advance for your help, I’d really appreciate it.

I’ve forgot to mention I’m using Android for this development.

How do you add a virtual button? I’ve added a couple of them to my image target and their actions are triggered even without the user “touching” the button. What should I do?