Gravity-defying tweezers to improve medical implants

Cartilage implants that reduce the need for knee replacement operations could be a lot more advanced as researchers have developed a special kind of tweezers that use ultrasound beams to grip and manipulate tiny clusters of cells.

"Ultrasonic tweezers can provide what is, in effect, a zero-gravity environment perfect for optimising cell growth," said Martyn Hill, head of engineering sciences unit at University of Southampton in Britain.

Using ultrasonic sound fields, cartilage cells taken from a patient's knee can be levitated for weeks in a nutrient-rich fluid.

This means the nutrients can reach every part of the culture's surface and, combined with the stimulation provided by the ultrasound, enables the cells to grow and form better implant tissue than when grown on a glass petri dish.

By holding the cells in the required position firmly but gently, the tweezers can also mould the growing tissue into exactly the right shape so that the implant is truly fit-for-purpose when inserted into the patient's knee.

"As well as levitating cells, the tweezers can make sure that the cell agglomerates maintain a flat shape ideal for nutrient absorption," Hill added.

They can even gently massage the agglomerates in a way that encourages cartilage tissue formation.

"Ultrasonic tweezers have all kinds of possible uses in bioscience, nanotechnology and more widely across industry," said Bruce Drinkwater, professor at Bristol University in Britain.