For over 30 years, Barry Fox has trawled through the world's weird and wonderful patent applications, uncovering the most exciting, bizarre or even terrifying new ideas. His column, Invention, is exclusively online. Scroll down for a roundup of previous Invention articles.

Wing-sprouting drone

Unmanned aerial vehicles (UAVs) can fly where no pilot would dare and are hard to shoot down because they are so small. The trouble is, they also waste a lot of fuel taking off, so usually cannot stay airborne for too long.

But Daryl Elam of Arizona, US, is working on a drone that needs no fuel for take-off. It could simply be shot into the air like a shell, before sprouting wings for normal flight.

The drone's wings will be made of a tough textile, such as Kevlar, and will each contain a row of flexible hollow tubes. For launch, everything will be packed tight inside the shell. But, after reaching the right altitude, the shell will open a couple of side flaps to expose the folded wings and a pyrotechnic gas generator - similar to an airbag inflator - will blasts gas under pressure into the wing's tubes.

As the tubes inflate, they will expand and take on the taught shape of aerodynamic wings. The shell casing then becomes the UAV's fuselage, the wings provide lift and an onboard motor provides thrust.

The inventor reckons that, with careful packing, the stowed wings could be as small as one-thirty-fifth of their final in-flight volume.

Read the invention in full here.

Diamond transistors

Diamonds may be a microchip's best friend, too, it seems. Scientists at the University of Chicago and Argonne National Laboratory in the US have been making electronic transistors out of pure diamond.

The transistors can withstand far higher working temperatures than conventional ones, are resistant to corrosive chemicals and would even be safe to implant in body tissue, the inventor's patent suggests. The tricky part is making sure the diamonds connect and conduct properly.

To make them, pure diamond vapour is deposited at around 900°C to form a wafer base. More diamond vapour doped with nitrogen to make it conductive, is then layered on top.

Liquid molybdenum is then selectively deposited onto the conductive diamond, to make electrical contacts, and the sandwich is topped with even more diamond, this time mixed with hydrogen, to insulate it electrically. The molybdenum spots do not bond with the hydrogen-doped diamond, so they poke through the surface and act as connector electrodes.

All-diamond chips would be way too expensive for everyday civilian use, but the researchers have found a cheaper solution that works almost as well. Instead of a pure diamond wafer base, they use conventional silicon covered with a thin layer of insulating oxide, which is then coated with a layer of conductive diamond.

Read the full patent here.

Microwavable packaging

The UK's Ministry of Defence spin-off company, Qinetiq, has cooked up an interesting idea - a metal wrapping that helps keeps food cold but can also be used in a microwave without sparking and damaging the machine, as ordinary metal foil does.

The secret is to make the wrapping from thin polyester and cover it with tiny squares of aluminium, the Qinetiq patent reveals. The company has found that aluminium squares 300 micrometres wide, and spaced apart by 100-micrometre tracks of clear plastic, make the perfect heatwave-frequency filter.

Microwaves at the standard frequency and wavelength ignore the grid of squares and can cook the food as normal. But normal heat is reflected, to help keep the food cool.

Enough light passes through the polyester for a cook to see through the packaging and stored food will also stay fresh longer because the polyester is air-tight.

Read the full patent here.

Read previous Invention columns, featuring:

The drink-driver arm scanner, laser spark plugs, remote-controlled implants,the "I've been shot" gun, the snore zapper, the guitar phone, explosive-eating fungus, viper vision, exploding ink, the moody media player, the spy-diver killer, preventing in-flight interference, the inkjet-printer pen, sonic watermarks, the McDownload, hot-air plane, landmine arrows, soldiers obeying odours, coffee beer, wall-beating bugging, eyeball electronics, phone jolts, personal crash alarm, talking tooth, shark shocker, midnight call-foiler, burning bullets, a music lover's dream, magic wand for gamers, the phantom car, phone-bomb hijacking, shocking airport scans, old tyres to printer ink and eye-tracking displays.