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 all 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. These are not only limited to 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, facilitating advancements that can change people’s lives for the better.

Tribology plays a key role in the development of medicines, primarily in how medicines are delivered into the body, with particular focus 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 more obvious. The interfaces between a contact lens and an eyeball, and the contact lens and an eye lid are what drive how comfortable a contact lens is for its wearer. 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 in understanding how effective materials and coatings will be when in situ. For example, research is ongoing on the effectiveness of 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 industry 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 and 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

In Situ Viscosity Measurement of Confined Liquids

The viscosity of liquids governs crucial physical and engineering phenomena, ranging from diffusion and transport processes of nutrients and chemicals, …

The viscosity of liquids governs crucial physical and engineering phenomena, ranging from diffusion and transport processes of nutrients and chemicals, to the generation of friction and the physics of damping. Engineering fluids frequently experience local conditions that change their bulk rheological properties. While viscosity data can easily be acquired using conventional rheometers, the results are not always applicable to fluids under engineering conditions. This is particularly the case for fluids being sheared at high pressure under severe confinement, which experience very high shear stresses and often show extensive shear thinning. There is a lack of suitable methods for measuring fluid viscosity under such conditions. This work describes a novel in situ viscosity measurement technique to fill this gap. It involves the quantification of the fluorescence lifetime of a fluorescent dye that is sensitive to viscosity. The capability of the developed technique is verified by taking measurements in submicron thick films of two model fluids confined in a ball on flat contact. Viscosity measurements were successfully performed at pressures up to 1.2 GPa and shear rates up to 105 s−1. Spatial heterogeneity in viscosity caused by variations in pressure within the thin fluid film could be observed using the technique. It was also possible to detect differences in the rheological responses of a Newtonian and a non-Newtonian fluid. These first in situ high pressure, high shear viscosity measurements demonstrate the versatility of the proposed technique in providing information on the viscosity in conditions where contemporary techniques are insufficient. More importantly it highlights the complexity of the rheology of engineering fluids and provides a means of verifying existing theories by performing in situ measurements. Information on local viscosity is crucial for understanding the physics of confined fluids and to facilitate improvements in engineering technology.

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Paper

Laser-induced Fluorescence for Film Thickness Mapping in Pure Sliding Lubricated, Compliant Contacts

A laser-induced fluorescence (LIF) technique has been used to measure fluid film thickness in a compliant, sliding contact under low-load/low-pressure …

A laser-induced fluorescence (LIF) technique has been used to measure fluid film thickness in a compliant, sliding contact under low-load/low-pressure conditions. The soft contact between an elastomer hemisphere and a glass disc is lubricated by a liquid containing fluorescent dye. The contact is then illuminated with 532 nm laser light through the glass disc, and viewed with a fluorescence microscope. From the intensity of emitted radiation, film thickness maps of the contact are determined. Previous calibration procedures have used a separate calibration piece and test specimen with possible errors due to differences in reflectivity between the calibration and test specimens. In the work reported in this paper a new calibration process is employed using the actual test sample, thereby avoiding such errors.

Results are reported for a sliding contact between PDMS and glass, lubricated with glycerol and water solutions under fully flooded and starved conditions. It was found that, for glycerol, the measured film thickness is somewhat lower than numerical predictions for both lubrication conditions. It is suggested that a combination of thermal effects and the hygroscopic nature of glycerol may cause the lubricant viscosity to drop resulting in thinner films than those predicted for fully flooded contacts. Starvation occurs above a critical entrainment speed and results in considerably thinner films than predicted by fully flooded I-EHL theory. A numerical study has been carried out to determine the effect of the observed starvation on film thickness. Predicted, starved film thickness values agree well with those obtained experimentally.

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