Scientists have long sought to replicate the shock-absorbing and lubricating properties of cartilage, with such a material undoubtedly having a range of applications in engineering and beyond. However, the bi-phase nature of cartilage – whereby it exists in both solid and fluid states, depending on the presence of synovial fluid in the joints – has proved difficult to reproduce.
Hydrogels can mimic cartilage’s lubricating properties, but do not retain structural integrity under compressive force. To overcome this problem, the researchers created a synthetic porous material made of a hydrogel held in a matrix of polydimethylsiloxane (PDMS), a silicone-based polymer that enables the hydrogel to maintain its shape under pressure.
“Scientists and engineers have been trying for years to develop a material that has the amazing properties of cartilage,” said lead researcher Dr Siavash Soltanahmadi, from Leeds’ School of Mechanical Engineering.
“We have now developed a material for engineering applications that mimics some of the most important properties found in cartilage, and it has only been possible because we have found a way to mimic the way nature does it.”
In Applied Polymer Materials, the scientists report that the load-bearing behaviour of the hydrogel held in the PDMS matrix was 14 to 19 times greater than the hydrogel on its own. The equilibrium elastic modulus of the composite was 452 kPa at a strain range of 10-30 per cent, similar to that of cartilage. The researchers believe future applications of the material could challenge traditional oil-lubricated engineering systems.
“The ability to use water as an effective lubricant has many applications from energy generation to medical devices,” said research supervisor Dr Michael Bryant, Associate Professor in the Leeds School of Mechanical Engineering.
“However this often requires a different approach when compared to traditional engineering systems which often use oil-based lubricants and hard-surface coatings.”