Basically, the doorknob is built so that it can physically retract into the door when the person on the inside wishes to not be disturbed.
Clever idea, but ultimately flawed. I’d like to discuss this from three perspectives.
I anticipate that we will start seeing technology like this advertised as a new security tool. On the surface, it makes sense. If the doorknob isn’t there, an intruder can’t get in, right?
Wrong. To draw an analogy to IT security, having a retractable doorknob is like having user account without a login. If the intruder can only get in through the door, then you did good and blocked the bad guy. However, the security of a system is only as strong as the weakest link. On a house, having a doorknob that is sometimes absent only prevents someone from coming in through the door. They could still break a window, saw through the siding, or kick the door in. In a hotel, it’s somewhat better, as most of the direct access points are either in public areas or sufficiently high to cause problems getting in. However, the door could still be kicked in and the room ransacked quickly enough to allow the perpetrator to get away.
This invention does not significantly enhance security.
Socially, all that this invention does is inform someone who is outside the door that the person inside wishes to be left alone. Traditionally, this is done with a little sign that says “Please do not disturb” and such.
I suspect that, in practice, this invention would result in more people knocking on the door to ask “Hey, where’s your doorknob?” than it would actually limit intrusion. Humans understand what a sign means. It’s been part of our culture for hundreds of years. People don’t understand what a retracting doorknob means. Much like the famous pay-to-ring doorbell, people can subvert the system as easily as knocking on a door. Unless this is paired with an un-knockable door, it does not improve the social situation. Instead, it hinders it.
Here we get down to brass tacks. Who is going to buy this thing? Probably hotel managers and builders. Possibly apartment managers. Possibly condominium builders. And why would they buy it?
Because it looks cool. Really, it does look remarkably cool, and as such, will be very popular with people trying to make places that appear “trendy”. Of course, one year from installation, most of the doors will be covered with stickers saying “Please do not knock” and “No door knob means do not disturb.”
Because people already know what signs mean.