Logic between Cell and knife sharpness

My question is
                   We can cut things with the help of knife but we cannot cut things with help of cell phone why?
   My answer
                  There is no secret behind this the matter is only the pressure of contact.Think like science student we not cutting things just we are seperating the bonds in that thing.A thing is made of group of atoms bonded in it if we seperate the bond between atoms so we can simply seperate the thing.So with knife we are cutting things because it can seperate the two things with its sharp edge.With the cell phone we cannot cut the things because it is easy to seperate the bonds with breaking the contact between them.pressure of contact should be equal to the pressure on the thing or object