https://medium.com/futurity-news/wasp-inspired-robots-open-doors-by-themselves-da2be5c1ad3a

Researchers have modified small flying robots to grab and haul heavy loads with the help of powerful winches and two previous inventions: gecko adhesives and microspines.

A closed door is just one of many obstacles that poses no barrier to a new type of flying, micro, tugging robot called a FlyCroTug. Outfitted with advanced gripping technologies and the ability to move and pull on objects around it, two FlyCroTugs can jointly lasso the door handle and heave the door open.