It might not look like much - but that’s the point. The mechanical insect in the video above is the world’s smallest camera-carrying ultra-miniaturised aircraft, or nano air vehicle (NAV), measuring less than 4in across and weighing in at an ant-like 0.1oz.

It is also one of the most sophisticated, able to buzz though the air at 10mph while the transmitter beams TV-quality images back to a base station a few hundred feet away.

Called the DelFly Micro, the machine has been likened to a robotic dragonfly and is built from ultra-light thermoplastic polymers, carbon fibre and micro-circuitry. A small lithium polymer battery gives it a flight time of three minutes.

It was unveiled last week by Delft University of Technology, in Holland, but it is only the latest in a series of nano air vehicles to take to the skies: the growing flock of NAVs worldwide includes pocket-sized helicopters, tiny rocket-powered wings and machines that mimic the flight of hummingbirds.

Full-size flying robots have been around for years. High-tech drones scout out terrorists and launch guided missiles in Afghanistan and Iraq while their “pilots” sit thousands of miles away in America. Less sophisticated drones are already being used by police forces in Britain to plan raids and monitor music festivals.

But the focus is now shifting towards designing intelligent, autonomous, miniaturised aircraft that can sneak unseen into even the most well-protect-ed airspace.

The driving force behind that focus is the military - specifically the US government’s Defence Advanced Research Projects Agency (Darpa). “We are interested in a system that has 20 minutes of flight time, can withstand 5mph wind gusts, can operate inside buildings and has a range of over 1,000 yards,” explains Todd Hylton, a Darpa programme manager. For several years, Darpa has been spending millions of dollars developing insect-sized aircraft that mimic nature, to gain a surveillance edge in future wars. These aircraft include a sycamore seed-like vehicle that uses a chemical rocket to spin almost silently through the air, controlled by a simple autopilot.

Darpa has just announced its top choice for the next generation of NAV development: the hummingbird-like Nano Scout from AeroVironment, a defence company. The Nano Scout (standing for Sensor Covert Observer in Urban Terrain) has rapidly flapping wings and a tailless design that enables it to hover, dash at up to 20mph and take off or land vertically. In return for its $2.3m (£1.1m) investment, Darpa expects to see a flying prototype next month.

When fully operational, these miniature aircraft will need the ability to navigate and seek out targets for themselves. “One of our test aircraft beams images to the ground station, where a computer performs calculations and sends control signals back to the engine,” says Bart Remes of Delft University. The development means that in future remote-control pilots will become redundant, and with the heavy, power-hungry electronic brains kept safely back at base, aircraft can be made lighter, faster and cheaper.

So just how small could these surveillance robots become? As scientists understand more about the physics of flight at very small scales, there’s little to hold them back. “We are now on our third generation of DelFly, and they keep getting smaller and smaller,” says Remes. “The next generation will be under two inches long. In the long term, we’re dreaming of an aircraft the size of a fruit fly.”

Explore Tech & Web

• Personal Tech

• The Web

• Gadgets & Gaming