Biomedical

By improving our understanding of how both natural and synthetic materials perform and interact within the human body, we aid the discovery and development of refined alternatives, enabling us to live a more fulfilling life.

Many would imagine biomedical tribology is limited to replacement joints, however, this is not the case. Research has long been conducted to develop and improve the tribosystems found in a whole range of biomedical appliances, not only replacement joints but also contact lenses, medicines and dental implants to name a few. PCS’ instruments are used by researchers around the world to help push this work forward to make advancements that can change people’s lives for the better.

Tribology plays an important role in the development of medicines. This is primarily in how medicines are delivered into the body, with lots of work going on that is focussed on how smoothly both solid and liquid medicines can travel down the oesophagus, and whether they coat it as they do or slide straight through. For contact lenses, the importance of tribology is even more obvious. The interfaces between a contact lens and an eye ball, and the contact lens and an eye lid are what dictate the wearers comfort. Without in depth research and investigation of these interfaces, people could be left with uncomfortable or even dangerous lenses.

For replacement joints tribological research is vital for understanding how effective materials and coatings will be when in situ. For example a lot of research is being conducted on replacement synovial joints. These joints (e.g. knee and hip joints) are continuously transmitting large dynamic loads whilst accommodating a wide range of movements. Due to trauma and diseases, such as osteoarthritis, these joints occasionally need to be replaced by artificial implants. Tribology research considers the friction, wear and lubrication of natural and artificial joints including the wear debris from the joint implants and the human body’s reaction to this.

Biomedical research areas include:

  • Contact lenses
  • Prosthetics
  • Replacement joints
  • Pharmaceuticals
  • Dental fillings

Biomedical Industry includes the following:

Artificial Joints

Artificial Joints

Artificial joints typically comprise of two surfaces rubbing against each other, the core of tribology. Researchers conduct extensive work examining this interaction between parts how they will act when in the body.

Biomaterials

Biomaterials

Biomaterials, be they artificial or natural, interact with biological systems. The study of this interaction is crucial in designing biomaterials that work harmoniously with the world around us.

Dental

Dental

Teeth interact daily with each other, with food and with your toothbrush. Understanding these contacts is important for designing everything from toothbrushes, to replacement teeth and implants.

Ocular

Ocular

The eye is a particularly delicate tribosystem and is an area of intense research. The contact lens-to-eye and to eye lid interfaces must be perfect to make sure they stay comfortable and in place all day.

Orthopaedics

Orthopaedics

A greater understanding of the body and how different joints work, how they degrade and how they can be damaged is being gained from tribological research into orthopaedics.

Pharma

Pharma

Tribology is a common research area in pharma for many reasons, an example is how pills and liquid medicines interact with the oesophagus, whether they need to coat it or slide smoothly through.

Instruments for the Biomedical Industry

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Biomedical Industry Articles & Papers

Paper

Capillary Rheometer for Magnetic Fluids

Magnetic fluids have been around since the 1940’s. They come in different forms: Magnetorheological fluids (MR fluids) and Ferrofluids. MR …

Magnetic fluids have been around since the 1940’s. They come in different forms: Magnetorheological fluids (MR fluids) and Ferrofluids. MR fluids characterise themselves by having a large change in viscosity under the influence of a magnetic field. Ferrofluids have a significantly smaller change in viscosity however ferrofluids are colloidal suspensions. After their discovery many applications followed, such as the MR clutch, magnetic damper and bearing applications, in which the fluids are subjected to ultra high shear rates. Little knowledge is available on what happens to the rheological properties under these conditions. In general, the characteristics determined at lower shear rates are extrapolated and used to design new devices. Magnetic fluids have potential in the high tech and high precision applications and their properties need to be known in particular at shear rates around 106 s −1 . Commercially available magnetorheometers are not able to measure these fluids at ultra high shear rates and are limited to 105 s −1 . Therefore a new magnetorheometer is required to measure ultra high shear rates. In this paper the physical limitations of current measuring principles are analysed and a concept is designed for ultra high shear rate rheometry in combination with a magnetic field. A prototype is fabricated and the techniques used are described. The prototype is tested and compared to a state of the art commercial rheometer. The test results of the prototype rheometer for magnetic fluids show its capability to measure fluids to a range of 104 s −1 to 1.16 × 106 s −1 and the capability to measure the magnetorheological effect of magnetic fluids.

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Paper

In-situ Observations of the Effect of the ZDDP Tribofilm Growth on Micropitting

The ongoing trend for using ever lower viscosities of lubricating oils, with the aim of improving the efficiency of mechanical …

The ongoing trend for using ever lower viscosities of lubricating oils, with the aim of improving the efficiency of mechanical systems, means that machine components are required to operate for longer periods under thin film, mixed lubrication conditions where the risk of surface damage is increased. For this reason, the role of zinc dialkyldithiophosphate (ZDDP) antiwear lubricant additive has become increasingly important in order to provide adequate surface protection. It is known that due to its exceptional effectiveness in reducing surface wear, ZDDP may promote micropitting by preventing adequate running-in of the contacting surfaces. However, the relationship between ZDDP tribofilm growth rate and the evolution of micropitting has not been directly demonstrated. To address this, we report the development of a novel technique using MTM-SLIM to obtain micropitting and observe ZDDP tribofilm growth in parallel throughout a test. This is then applied to investigate the effect of ZDDP concentration and type on micropitting. It is found that oils with higher ZDDP concentrations produce more micropitting but less surface wear and that, at a given concentration, a mixed primary-secondary ZDDP results in more severe micropitting than a primary ZDDP. Too rapid formation of a thick antiwear tribofilm early in the test serves to prevent adequate running-in of sliding parts, which subsequently leads to higher asperity stresses and more asperity stress cycles and consequently more micropitting. Therefore, any adverse effects of ZDDP on micropitting and surface fatigue in general are mechanical in nature and can be accounted for through ZDDP's influence on running-in and resulting asperity stress history. The observed correlation between antiwear film formation rate and micropitting should help in the design of oil formulations that extend component lifetime by controlling both wear and micropitting damage.

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