Biomimicry : Scientists studied the anatomy of mosquitoes to create a painless hypodermic needle.

A needle, making injections painless, by mimicing the mosquito’s unique “stinger”, has been developed by a team of Japanese microengineers.

Contrary to popular belief, a mosquito can stab you with its proboscis without you feeling a thing. It then injects anticoagulant saliva to stop your blood clotting while it feeds, and it is this that carries the bacteria that cause irritation and pain.

The initial bite is painless because the mosquito’s proboscis is highly serrated. The jagged edge of the proboscis leaves only small points in contact ,Unlike the smooth surface of a syringe needle, which leaves a lot of metal in contact with skin tissue . This greatly reduces stimulation of the nerves, causing far less pain.

To mimic this effect, engineering team created a needle just one millimetre long and 0.1 millimetres in diameter. They did this by etching slices of silicon dioxide into a jagged shape and then bonding them together. The needle’s walls were just 1.6 um thick.

Then they fitted the needle with a five-millimetre-wide tank, which in future could store blood or fluids collected by the needle. An optical fibre inserted in the tank would allow doctors to analyse samples.

In order to test the strengthof needle, the researchers pushed the needle into a piece of silicone rubber, which has puncture resistance same as that of skin – wrapped around a vessel containing a red dye. The tank filled with the dye, indicating that the needle is up to the challenge of puncturing skin.