The cover around the panel is the highest point, so if you lay it flat on the table, the panel does not touch the surface. The panel itself is made from a base pcb (glassfiber+epoxy) and covered in epoxy. I would say it is pretty durable and if you manage to make some scratches you have about 1mm of epoxy before you reach the photovoltaic cell, so safe to polish. Should be fine. Would worry more about the front of your phone