Borrow any smartphone from anyone. Show ordinary red silk. Place one end of the silk onto the screen of the borrowed phone. Remove your hand and one end of the silk is now seen to be penetrated inside the phone. Your hand is completely empty, the silk is hanging by itself with one end that went inside the middle of the borrowed phone.
Now your one hand is gripping the phone just by the fingers, and your free hand starts pulling the silk from the back of the phone. The silk from the front is clearly seen going through the middle of the phone until it completely comes out of the other side. The screen can be seen to be completely intact with no hole in it. The phone is shown clearly, slowly, front and back that it is completely normal without any damage, and immediately returned to the owner.
The gimmick is completely invisible, very effective, and simple to handle. Your spectator will be looking directly at the gimmick but will not see it. Similar to what you do with invisible threads. It is there, but they cannot see it. Easy to learn and an extremely visual effect that you can perform immediately.