Im not sure if we have any chemists amongst us here but was pondering as you do....
Would it be possible to design a material that can be sheered under certain conditions and also 'heal itself' under the reverse of those conditions...
for example.
Two plates of 'material x' on a door and frame that contact upon closure.
A current (or whatever is required to initiate the reaction) is passed through the plates causing them to bind permanently into one solid item, and thus permanently securing door until the reverse reaction is taken place.
Its a little hard to visualize if you dont know what i mean.
Im pretty sure this is within the capabilities of modern chemistry/Physics
Ok its far fetched but would be pretty cool to have a door that you could 'heal' closed, into a wall lol