sensitive switch on wash machine

I would like to simulate a press on the start button (sensitive switch) of my wash machine. Is there any way to do this without modifying the wash machine panel ? Which hardware would be involved ?

Do you mean pressure sensitive or capacitive sensor? There should all kinds of creative ways to fool a capacitive switch. But then again, engineers have been hard at work for quite some time on detecting, then ignoring, those kinds of inputs. If you feel qualified enough to not shock, maim or kill yourself, you should take it apart and examine it under operation. You need to be safe and check things first, but it should be fairly obvious where it's low voltage and where it's got A/C present by the size and type of wire used.