Earlier this year, Boston Dynamics revealed that its SpotMini robot was now capable of opening doors using a manipulator arm. But though it's called Mini, this four-legged bot may not be small enough to get into tight spaces or move through crumbling ruins caused by an earthquake. A micro-drone might be better suited to such situations. Even better if it could do some heavy lifting too. Researchers at Stanford University have modified teeny flying robots so that they can squat down and move objects 40 times their weight.

The Stanford researchers have named their creation the FlyCroTug, which describes what it's capable of – flying, crouching and tugging. Its small size means that it can fly through small spaces and get fairly close to people, which will come in handy for search and rescue situations.

The mini-drones can fly to a disaster site, land and temporarily cement themselves to a variety of surfaces. This is made possible thanks to either gecko-inspired adhesives for smooth surfaces or 32 hook-like microspines inspired by insects for rough surfaces, both of which were previously developed at the Biomimetics and Dexterous Manipulation Lab.

"Wasps can fly rapidly to a piece of food, and then if the thing's too heavy to take off with, they drag it along the ground," said the lab's Mark Cutkosky. "So this was sort of the beginning inspiration for the approach we took."

Each FlyCroTug has been fitted with a small winch so that when it lands, tit can pull debris up to 40 times their weight out of the way, lower a camera to allow rescue personnel to survey the area or even open doors.

With a closed door as the obstacle, a single FlyCroTug might find keeping the handle down and tugging the door open a tad taxing, so the researchers got two of them to work together, as you can see in the video below.

"People tend to think of drones as machines that fly and observe the world, but flying insects do many other things – such as walking, climbing, grasping, building – and social insects can even cooperate to multiply forces," said Dario Floreano of Switzerland's École Polytechnique Fédérale de Lausanne, who also worked on the project. "With this work, we show that small drones capable of anchoring to the environment and collaborating with fellow drones can perform tasks typically assigned to humanoid robots or much larger machines."

A paper detailing the project has been published in Science Robotics.