快猫短视频

A POLYMER that makes submarines vanish will soon be helping sports physiotherapists treat injuries. The plastic will ensure their ultrasound devices don鈥檛 dangerously overheat muscle tissue 鈥� or do nothing at all.

Until now, there has been no easy way to check the power output of physio ultrasound machines, which are often used for treating sports injuries to limbs. As a result, many machines deliver acoustic power that can be at least 30 per cent adrift of the level they are set to deliver, according to Stephen Pye, a medical physicist in Edinburgh.

Such machines can produce local hot spots in muscle, in some cases damaging tissue. And some machines are simply broken and have no output at all. It can take months before anyone notices the fault, says Pye.

Now the National Physical Laboratory in Teddington, Middlesex, has come to the rescue. Its 鈥減owermeter鈥� comprises a simple water-filled vessel with a base made of two layers of different polymers. The top one is polyvinylidene fluoride, a 鈥減yroelectric鈥� material that produces a voltage when heated. Beneath this is a layer of dense polyurethane rubber that is also used to coat submarines, because it turns 80 per cent of the ultrasound energy that strikes it into heat, reducing the subs鈥� 鈥渟onar signature鈥�.

To work out the power output, the physio simply dunks the ultrasound head in the water chamber. The sound energy is converted to heat by one polymer, and the heat is turned into a voltage by the other, accurately reflecting the ultrasound鈥檚 power. Precision Acoustics of Dorchester, Dorset, plans to market the technology later this year.