Japanese microengineers created a minute needle just one millimetre long and with a diameter of 0.1 millimetres. They etched slices of silicon dioxide into a jagged shape and bonded them together. There are two serrated shanks that form the outer surface of the needle. A central shaft then slides between them to inject or withdraw the sample. The needle is connected to a small reservoir that is equipped with an optical sensor to analyze samples.
Current needles are relatively smooth cylinders that present large amounts of surface area to nerves, causing pain to the human subject.
A mosquito's initial bite is actually quite painless. The highly serrated proboscis touches the nerves of the skin at fewer points than a smooth surface like a needle. Much less contact area translates into much less pain. These seven moving parts consist of various serrated outer segments (maxillae) and a smooth inner shaft (labrum).Reference Article:Izumi H, Suzuki M, Aoyagi S, Kanzaki T. 2011. Realistic imitation of mosquito's proboscis: Electrochemically etched sharp and jagged needles and the cooperative inserting motion. Sensor Actuat A:Phys. 100(1): 115-123.
Reduced pain for injecting or drawing blood samples. Small biomedical devices, for instance used in diabetic patients to monitor blood-glucose levels.