3D Printed Protective Face Mask For Athletes

It’s really hard to miss out on the news about football players wearing Zorro’s masks during the games. When Son Heung-min showed up at the Qatar World Cup as South Korea face Brazil, wearing that shining, chic, black face mask, everyone on the internet was talking about it. Actually, many football players have been seen wearing similar masks to the match, including Croatian player Joško Gvardiol and Tunisia’s Ellyes Skhiri as in the cover picture. So, what are these face masks for and how are they made?

Example of 3D Printed sports face orthotic

Protective face masks have been loved by many athletes who have recently fractured a nose or an eye socket but are eager to get back to the pitch as soon as possible. The 3D surface imaging, 3D modelling, and 3D printing technology enable the design process to be accurate and customisable, 100% specific to the face of the athletes. The masks are designed to be lightweight, comfortable and unobtrusive, but provide incredible strength to protect fractured bones or prevent future injury.



Header Image Adapted from: https://www.theguardian.com/football/2022/nov/28/why-are-world-cup-players-wearing-strange-face-masks-on-the-pitch



This post was written by Esperanza Shi as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Esperanza is researching the Optimisation of Scanning Strategies for 3D Printed Artificial Joints at Imperial College London, UK.

BioTrib Conversations: ChatGPT on biotribological research

Generative text AI tools, such as ChatGPT, have recently garnered significant attention due to its ability to provide comprehensive responses and eloquent answers across many domains of knowledge. Whilst it represents a significant technological advancement, it has been met with both positive and negative reviews. Elon Musk wrote that “ChatGPT is scary good”. It has also received widespread criticism particularly around efficacy and integrity from educators, academics and journalists plus many more.

But how should we embrace these tools? Professor Michael Bryant asks ChatGPT ‘What are the current research challenges in biotribology?’

Biotribology is the study of friction, wear, and lubrication of biological systems, including joints, implants, and prosthetics. Some of the current research challenges in biotribology include:

1. Understanding the complex interactions between biological tissues and synthetic materials: One of the major challenges in biotribology is to understand the complex interactions between biological tissues and synthetic materials used in implants and prosthetics. This requires a deep understanding of the mechanical, chemical, and biological properties of both the biological tissues and the synthetic materials.

2. Developing advanced testing methods: Biomechanical testing of biological tissues is challenging due to their complex nature. Developing advanced testing methods that can accurately measure friction, wear, and lubrication in biological systems is a critical research challenge.

3. Designing and developing better implant materials: Developing new materials and coatings for implants that can better mimic the natural properties of biological tissues is another important research challenge. This can help improve the biocompatibility, durability, and longevity of implants.

4. Improving lubrication of joint replacements: The lubrication of joint replacements is a critical factor in their performance and longevity. Developing better lubrication strategies and materials is a key research challenge in biotribology.

5. Studying the effects of aging and disease: Aging and disease can significantly impact the friction, wear, and lubrication of biological systems. Studying the effects of aging and disease on biotribology can provide valuable insights into the development of better treatments and therapies for patients.

It is a good job BioTrib is working across all of these domains to address the current research challenges highlighted by ChatGPT. What will be interesting to see is how these changes with time as the field advances. Certainly some of these challenges have been of focus to researchers for many a year.

This article was written by ChatGPT and BioTrib Lead Scientist, Professor Michael Bryant.

Alginate based bioinks for 3D bioprinting of engineered orthopedic tissues

Alginate is widely used as a biomaterial in 3D bioprinting due to its biocompatibility, biodegradability, high accessibility, shear thinning behavior, and cross-linking speed. The rheological properties of the bioink are the key factor influencing printability (ability to form and maintain the design shape), therefore investigations are conducted to enhance the weak mechanical properties of alginate gel in order to obtain hybrid hydrogels with high printability. Indeed, when using 3D bioprinting, the objective is to obtain a multilayer construction that retains its mechanical stability over time and, in order to produce relevant in vitro tissue models, the final goal is to match the native mechanical properties of the tissue.

In the review ‘Alginate based hydrogel inks for 3D bioprinting of engineered orthopedic tissues’, Murab et al. provide an overview of the different parameters such as printing method, concentration of alginate and crosslinker, and shape of the printed structures on the properties of the alginate-based printed construct. Specifically, they reviewed different strategies used in the last few years to increase the mechanical and biological performances of alginate-based hydrogels for bioprinting of bone and cartilage. For example, the advantageous properties of alginate and type I collagen have been combined to create a lattice structure with improved mechanical properties and higher expression of cartilage-specific genes in primary rat articular cartilage chondrocytes compared to the alginate control.

Another example of cartilage tissue engineering using alginate combined the latter with polycaprolactone (PCL) to create a stable PCL support scaffold with bioprinted alginate in between. The resulting construct exhibits good mechanical stability and the goat cartilage cells embedded in alginate were found to have high viability with the production of a cartilage-like matrix. Although encouraging results are presented in the literature, there is still a long way to go to use the alginate-based hydrogels for in vitro orthopedic models.



Murab, Sumit, et al. “Alginate based hydrogel inks for 3D bioprinting of engineered orthopedic tissues.” Carbohydrate Polymers (2022): 119964.


This article was written by Marie Moulin as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Marie is researching the Bioprinting of Bone and Cartilage at Uppsala University, Sweden.

Volumetric Bioprinting of Meniscus

The fabrication of functional constructs that mimic the physiological characteristics of tissues would represent a major breakthrough for the creation of complex in vitro models or for regenerative medicine. Current 3D biofabrication technologies, such as stereolithography or extrusion bioprinting, are used to attempt to achieve this goal by combining cells and biomaterials according to a specific architecture, layer by layer. This additive manufacturing method limits the ability to create clinically relevant sized constructs, as the printing time for centimeter-sized constructs is too high to preserve cell viability (cells remain in the cartridge and construct, outside of an optimal culture environment). Volumetric bioprinting is a promising technology that could produce clinically relevant sized living constructs in less than a minute.

This emerging technology uses the principle of medical tomography in reverse, projecting a 2D patterned optical light field into a volume of photopolymer, which causes cross-linking in the area where the light exposure builds up to produce a 3D construct. Paulina Nuñez Bernal et al. described in 2019 the utilisation of this technic to create a 3D meniscus-shaped construct with high resolution, high cell density, and cell viability (>85%). To do so, a gelatin-based photoresponsive hydrogel (gelMA) containing chondroprogenitor cells (ACPCs) was used. Over time, the cells in the printed constructs synthesized fibrocartilage ECM, which increased the mechanical properties of the meniscus to a compressive modulus value comparable to that of native fibrocartilage. This achievement using volumetric bioprinting could be promising for the future of knee joint repair.



Bernal, Paulina Nuñez, et al. “Volumetric bioprinting of complex living‐tissue constructs within seconds.” Advanced materials 31.42 (2019): 1904209.


This article was written by Marie Moulin as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Marie is researching the Bioprinting of Bone and Cartilage at Uppsala University, Sweden.

Wettability in biotribology applications

Wettability enhancement can improve the lubrication conditions by forming the tribofilm on the surface, reducing wear rate and friction coefficient[1];one of the way is by grafting hydrophilic acrylic acid on UHMWPE. The presence of carboxylic groups in the acrylic acid enhances the interaction with the bioactive molecules such as proteins, peptides, etc. With the grafting ratio of 5.5% , the water contact angle reduced from 83o to 35o due to the great polarity and affinity for water by the carboxyl group present in the acrylic acid. As the surface wettability improves with the graft ratio, the tensile strength decreases while the wear rate declines initially and starts to rise again. Another study done by the Lu et al.[2] on ultrasonically infiltrated with GO mixed with UHMWPE significantly changed the wettability. The surface wettability increased with the increase of ultrasound-induced time resulted in the reduction of COF and wear rate. There are various studies suggesting the improvement in the tribological properties with the enhancement of surface wettability. However, the tribological properties does depend on other various factors such as sliding speed, surface topography, materials properties, sliding temperature, applied load and pressure etc.

Figure 1 a) hydrophobic surface b) hydrophillic surface [5]
Similarly, it is not as straightforward for the bio-compatibility of materials. Wettability influences the protein adsorption, blood coagulation, bacterial adhesion, cell adhesion, platelet adhesion/activation etc [3]. Osteoblast adhesion were decreased with the increase in contact angle from 0o to 106o while fibroblast adhesion was maximum between contact angles 60o to 80o[4]. Various studies mentioned that the hydrophobic surface suitable for the cell spreading, proliferation and differentiation while the hydrophillic surface enhances the cell attachments, proliferation and differentiation [4,5,6]. Adsorption of water molecules is higher in superhydrophilic surfaces preventing protein adhesion which might lead to lower cell adhesion. Thus, moderate hydrophilicity surfaces are most effective for cell adhesion and proliferation. However, the other argument is better cell proliferation and differentiation on superhydrophobic surfaces as the cells would have more surface area available for attachment and proliferation.

Wettability properties can be measured by different methods such as contact angle measurements and Wilhelmy plate method. Understanding the wettability properties of a material can be useful in controlling the tribological behavior and the biocompatibility of a material in biotribological applications.


[1] Y. Deng, D. Xiong, and K. Wang, “Biotribological properties of UHMWPE grafted with AA under lubrication as artificial joint,” J Mater Sci Mater Med, vol. 24, no. 9, pp. 2085–2091, Sep. 2013, doi: 10.1007/s10856-013-4970-x.
[2] P. Lu, M. Wu, X. Liu, X. Ye, W. Duan, and X. Miao, “Surface modification and biotribological behavior of UHMWPE nanocomposites with GO infiltrated by ultrasonic induction,” J Biomed Mater Res B Appl Biomater, vol. 109, no. 6, pp. 808–817, Jun. 2021, doi: 10.1002/JBM.B.34746


This article was written by Dilesh Raj Shrestha as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Dilesh is researching the Development of 3D-printable, self-lubricated polymer composites with improved wear resistance for total joint replacement at Luleå University of Technology, Sweden.


Biotribological Lubrication Mechanisms

The joints experience the dynamic environment (load, speed), thus the various mode of lubrication mechanism can exist. However, number of lubricating mechanism has been proposed over the time such as weeping/squeeze film, boosted, boundary, elasthydrodynamic, micro-elastohydrodynamic, and mixed [1]–[3]. Friction and wear of any tribological systems can be influenced by the materials property, surface properties, operating conditions and the environment[4]. Since synovial joints are among the complex and sophisticated tribological systems, so it is likely that many mode of lubrication mechanisms are present.

Figure 1: Lubrication mechanism for right hip joint

If anyone walks, the interface might be lubricated with synovial fluid via the number of processes such as hydrodynamic, squeeze film/weeping, etc by supporting the load wherever it can. The synovial fluid is squeezed out under loading and consequently lubricates the articular cartilage during off loading(see figure 1). Some of the studies suggest that the synovial fluid cannot separate the articulating surface all the time [5]. When a synovial joint experience the continuous load such as standing for a longer duration, all the fluid is squeezed out of the contact and the load bearing surfaces experiences the boundary lubrication mechanism where the two articulating surface rub with each other. Thus, it can be concluded that synovial joints can encounter the fluild-film, mixed and boundary lubrication similar to the engineering bearings[1]. Murakami et al. [6] termed it as a ‘adaptive multimode lubrication’. The main three mechanism widely studied after their introduction are biphasic lubrication (a form of full film lubrication, since introduced by Mow et al. [7], electrohydrodynamic lubrication (since introduced by Dowson) and brush lubrication(a form of boundary lubrication, since introduced by Hardy et al. [8].

There is limited information on the lubrication mechanism on the artificial total joint replacement. Lubrication mechanism in artificial joints have more variables than the natural synovial joints such as material used, design, contact conditions, patient specific factors, surgical factors etc. Many designers believed that the full film lubrication is difficult to achieve so the efforts have been made towards the improvement in boundary and dry lubricated wear behaviour of implants[9], [10]. Based on the boundary lubrication theory, Charnley[11] developed the low friction arthroplasty using UHMWPE as the acetabular cup combined with the stainless steel femoral head in total hip replacement resulting low wear. In addition to this, various implant design were proposed based on fluid film, elasto-hydrodynamic, elasto-mixed etc[1].

Suitable selection of design parameters (head diameter, diametral clearance etc.) promotes the contact to undergo full hydrodynamic lubrication in hard/hard bearings implants[12]. For instance, when the head diameter is small(16 to 22.5 mm) the surface is under boundary lubrication regime, and when the head diameter is 28 mm it is under mixed lubrication regime[13]. This is because of the tendency to provide surface separation for considerable amount of gait cycle and hence evidence of lubricating film formation. Also, with the increase in the diameter results in higher sliding area which will increase the wear under boundry or mixed lubrication regime. To conclude, it is obvious that the all boundary, mixed and elasto-hydrodynamic lubrication mechanism have been supported by the past studies but most of the implants likely experienced mixed lubrication regimes more than other two.  Continuous studies are being carried out in order to mimic the natural synovial joints which undergoes full range of conditions.


This article was written by Dilesh Raj Shrestha as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Dilesh is researching the Development of 3D-printable, self-lubricated polymer composites with improved wear resistance for total joint replacement at Luleå University of Technology, Sweden.



[1] D. Dowson, “Bio-tribology,” Faraday Discuss, vol. 156, no. 0, pp. 9–30, Jul. 2012, doi: 10.1039/C2FD20103H.
[2] D. J. Groen and A. Unsworth, “Tribology of Human and Artificial Joints,” http://dx.doi.org/10.1243/PIME_PROC_1991_205_287_02, vol. 205, no. 3, pp. 163–172, Aug. 2016, doi: 10.1243/PIME_PROC_1991_205_287_02.
[3] M. J. Furey and B. M. Burkhardt, “Biotribology: Friction, wear, and lubrication of natural synovial joints,” Lubrication Science, vol. 9, no. 3, pp. 255–271, May 1997, doi: 10.1002/LS.3010090303.
[4] R. K. Nanstad, “Encyclopedia of Materials Science and Engineering, ed. MB Bever.,” Pergamon Press, New York, 1986.
[5] C. W. McCutchen, “Lubrication of and by Articular Cartilage,” Cartilage, pp. 87–107, Jan. 1983, doi: 10.1016/B978-0-12-319503-6.50009-8.
[6] T. Murakami, H. Higaki, Y. Sawae, N. Ohtsuki, S. Moriyama, and Y. Nakanishi, “Adaptive multimode lubrication in natural synovial joints and artificial joints,” Proc Inst Mech Eng H, vol. 212, no. 1, pp. 23–35, 1998, doi: 10.1243/0954411981533791.
[7] V. C. Mow, S. C. Kuei, W. M. Lai, and C. G. Armstrong, “Biphasic Creep and Stress Relaxation of Articular Cartilage in Compression: Theory and Experiments,” J Biomech Eng, vol. 102, no. 1, pp. 73–84, Feb. 1980, doi: 10.1115/1.3138202.
[8] W. B. H. Akdy, “Boundary lubrication.—The temperature coefficient,” Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, vol. 101, no. 713, pp. 487–492, Sep. 1922, doi: 10.1098/RSPA.1922.0060.
[9] T. MURAKAMI, “The Lubrication in Natural Synovial Joints and Joint Prostheses,” JSME international journal. Ser. 3, Vibration, control engineering, engineering for industry, vol. 33, no. 4, pp. 465–474, Dec. 1990, doi: 10.1299/JSMEC1988.33.465.
[10] D. D., “Are our joint replacement materials adequate?,” Proc. Instn. Mech. Engrs, Int. Conf. The Changing Role of Engineering in Orthopaedics, 1989, vol. 1, 1989, Accessed: Jan. 17, 2023. [Online]. Available: https://cir.nii.ac.jp/crid/1573950399846027776
[11] J. Charnley, “Low Friction Principle,” Low Friction Arthroplasty of the Hip, pp. 3–15, 1979, doi: 10.1007/978-3-642-67013-8_2.
[12] Z. M. Jin and D. Dowson, “A full numerical analysis of hydrodynamic lubrication in artificial hip joint replacements constructed from hard materials,” http://dx.doi.org/10.1243/0954406991522310, vol. 213, no. 4, pp. 355–369, Aug. 2016, doi: 10.1243/0954406991522310.
[13] S. L. Smith, D. Dowson, and A. A. J. Goldsmith, “The effect of femoral head diameter upon lubrication and wear of metal-on-metal total hip replacements,” http://dx.doi.org/10.1243/0954411011533724, vol. 215, no. 2, pp. 161–170, Aug. 2016, doi: 10.1243/0954411011533724.

General influence of polymer crystallinity on biotribological applications

Crystallinity is a fundamental property of polymers that describes the degree of order in their molecular structure. It can have a significant impact on the tribological properties of a material in biotribological applications. The tribological properties of a material refer to its behavior during friction, wear and lubrication. In general, polymers with higher crystallinity tend to have better mechanical and thermal properties, such as increased strength and stiffness, as well as better wear resistance. This is due to the fact that the ordered arrangement of molecules in a highly crystalline polymer allows for stronger intermolecular interactions, leading to a more durable material.

Figure 1 Microscale (tribometer) friction response of UHMWPE using a diamond probe as a function of normal load (Karuppiah et al. 2008)
Figure 1 Microscale (tribometer) friction response of UHMWPE using a diamond probe as a function of normal load (Karuppiah et al. 2008)

In contrast, polymers with lower crystallinity tend to have poorer mechanical properties and increased wear. The disordered arrangement of molecules in these materials leads to weaker intermolecular interactions, making them more susceptible to deformation and wear. In biotribological applications, such as artificial joint replacements, this can lead to increased wear on the implant and a shorter lifespan for the device.

Crystallinity also affects the coefficient of friction of a polymer. Polymers with higher crystallinity tend to have a lower coefficient of friction, as the orderly arrangement of molecules allows for less deformation and better sliding properties. In contrast, polymers with lower crystallinity tend to have a higher coefficient of friction, as the disordered arrangement of molecules leads to increased deformation and poorer sliding properties. This can be a significant issue in biotribological applications where low friction is desired, such as in artificial joint replacements or in biomedical devices that need to slide against living tissue.

Furthermore, Crystallinity can also have an impact on the biocompatibility of a polymer. Polymers with higher crystallinity tend to be more biocompatible, as they are less likely to cause an inflammatory response in the body. In contrast, polymers with lower crystallinity tend to be less biocompatible, as the disordered structure of the polymer can lead to an increased risk of an inflammatory response.

In conclusion, Crystallinity is a crucial property that plays a significant role in the tribological properties of a polymer, including wear resistance, coefficient of friction, and biocompatibility. In biotribological applications, such as artificial joint replacements, it is important to carefully consider the crystallinity of a polymer when selecting materials. The crystallinity of a polymer can be controlled by various methods such as thermal treatment, addition of additives, and so on. Therefore, by understanding the effects of crystallinity on the tribological properties of a polymer, scientists and engineers can make more informed decisions when designing and developing biotribological devices.



Wang and S. Ge, “The mechanical property and tribological behavior of uhmwpe: Effect of molding pressure,” Wear, vol. 263, no. 7-12, pp. 949–956, 2007.

K. Karuppiah, A. L. Bruck, S. Sundararajan, J.Wang, Z. Lin, Z.-H. Xu, and X. Li, “Friction and wear behavior of ultra-high molecular weight polyethylene as a function of polymer crystallinity,” Acta Biomaterialia, vol. 4, no. 5, pp. 1401–1410, 2008.


This article was written by Dilesh Raj Shrestha as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Dilesh is researching the Development of 3D-printable, self-lubricated polymer composites with improved wear resistance for total joint replacement at Luleå University of Technology, Sweden.

PhD as an International Student

Pursuing a PhD as an international student can be a challenging but rewarding experience. It requires a great deal of dedication, hard work and a willingness to adapt to a new environment. However, with the right preparation and mindset, an international student can successfully navigate the PhD journey.

One of the first steps in pursuing a PhD as an international student is researching universities and finding the right program that fits your academic and career goals. Look into the universities that offer the program you are interested in and ensure they have a good reputation, vital research programs in your field of study and a diverse student population. Additionally, research the availability of funding and scholarships for international students as well as the cost of living in the area.

Another important aspect is ensuring that you meet the academic requirements for the program and that your academic background aligns with the program. For example, many universities require international students to take additional English language proficiency exams such as TOEFL or IELTS.

It’s also crucial to be aware of cultural differences and be prepared to adapt to a new environment. This may include learning about the customs and traditions of the country you will be studying in and being open to trying new foods and experiencing different ways of life.

Networking and building relationships with other students and professors are also essential. These connections can help you navigate the academic and social aspects of being an international student. Joining student organisations or clubs can also be a great way to make friends and feel more at home.

Lastly, taking care of your physical and mental health throughout your PhD journey is important. It may include finding ways to relax, de-stress, and stay active and healthy.

In summary, with the proper preparation, mindset and support, an international student can successfully triumph the PhD journey and achieve their academic and career goals.

This article was written by Edona Hyla as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Edona’s research is focussing on Understanding the Nature, Origin and Degradation of Implant Debris at the University of Leeds, UK

Robotic-assisted joint replacement, the future of surgery?

Robotic-assisted joint replacement surgery is a relatively new advancement in the field of joint replacement. This type of surgery uses a robotic arm, called a robotic arm-assisted surgical system, to assist the surgeon in positioning and aligning the implant. The robotic arm is controlled by the surgeon, who uses it to make precise movements and adjustments during the procedure.

One of the main benefits of robotic-assisted joint replacement surgery is that it can help increase the procedure’s accuracy. The robotic arm can be programmed with a patient’s specific anatomy, allowing the surgeon to make precise cuts and align the implant in the required position. This can lead to better outcomes, such as an improved range of motion and a reduced risk of complications.

Another benefit is that the robotic arm allows the surgeon to visualise the surgical field better, which can help reduce the risk of nerve or blood vessel damage. Additionally, the robotic arm can also help reduce surgical time, leading to a faster recovery for the patient.

Robotic-assisted joint replacement surgery is still considered a relatively new technology and is not yet widely available. However, it is becoming more common in certain centres and is used for various joints, including the knee and hip.

It’s important to note that it’s not a replacement for the surgeon’s skill and judgement but rather an aid to enhance the precision and accuracy of the procedure. Your surgeon will be able to advise you on whether this type of surgery is appropriate for you, based on your specific condition and anatomy.

Overall, robotic-assisted joint replacement surgery is a promising advancement in the field of joint replacement that has the potential to improve outcomes and reduce recovery time for patients.


This article was written by Edona Hyla as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Edona’s research is focussing on Understanding the Nature, Origin and Degradation of Implant Debris at the University of Leeds, UK

Roughness & Fractal Surfaces, but what are they?

Have you ever wondered why looking at a country map from the top looks so good with defined coastlines, yet when we are actually at a point on the edge, it really isn’t an edge rather a series of perturbances?

A question comes to mind, as to how exact is the length of the coast line then? Turns out, it depends on how smaller ruler one uses to measure the length of the coast, or what is the resolution of the map; the smaller scale would result in better estimation of coastline. But how small a scale could be, it might end up reaching to atomic scale then, a demonstration is shown in figure(1).

Figure 1: Fractal UK Coastline

While not an important question for many, it gave rise to the concepts of Fractal geometry. A generalized understanding of this concept was developed by Mandelbrot from 1960s onwards. As per this theory, a pattern repeats itself number of times if we keep zooming on that surface, known as “”self-affinity”” of the surface (figure 2). A coastline or dendrites generated during solidification can be treated as fractal in a more general sense. This concept was put forwarded to explain surface roughness as well, Archard foreshadowed to this concept in 1957 [2] to explain why coefficient of friction is constant when force-area relationship is non-linear during contact.

Figure 2: Self-Affinity of a fractal surface

As per this modern understanding of fractal geometries, a spherical asperity on a surface is rather a combination of multiple spherical asperities if we zoom in further, and then further it would show asperities on that surface as well. As per this concept, surfaces were treated as exactly self-affine however, surfaces are only approximately self-affine i.e. the scale of magnification between horizontal and vertical dimensions varies by an exponential factor “”H””, known as Herst exponent. Thus, for Archard’s case, the Herst exponent would be 1.


Figure 3: Fractal nature of rough surfaces


Further complex surface contact models based on fractal theory have been developed by Bhushan Pawlus, McCool, Buchner, Persson etc. Interested readers are pointed to [3] for further development. An interesting demonstration of fractal geometry can also be seen in this video demonstrating Fractals which are not self-similar [4].



[1] Gurung, Kris. (2017). Fractal Dimension in Architecture: An Exploration of Spatial Dimension.

[2] Archard J. F. (1957). Elastic deformation and the laws of frictionProc. R. Soc. Lond. A243190–205

[3] Barber, J.R. (2018). Contact of Rough Surfaces. In: Contact Mechanics. Solid Mechanics and Its Applications, vol 250. Springer, Cham.

[4] https://youtu.be/gB9n2gHsHN4


This article was written by Sallar Ali Qazi as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Sallar Ali Qazi is researching Mechanical and Tribo-Chemical Wear Modelling of Artificial Joint Prostheses at Imperial College London, UK

Meeting with UNICEF: What can we do to improve global arthroplasty?

BioTrib ESR, Ben Clegg had the pleasure of attending a small presentation at the UNICEF headquarters in Stockholm in December, with Ungaforskare

We had an engaging discussion on how we thought innovation could be used to improve our society. With a focused workshop on how we can service disadvantaged children in our turbulent world. What I gained from this is how we can improve and engage human connection to improve equality on all bases.

The meeting itself didn’t focus on anything specific within the medical industry, however it did stimulate a few thoughts on what we could do as early-stage researchers, something which was starkly aware of when discussing how we can aid the disadvantaged children in our previous discussions.

Within Biotrib we are all working towards an overall collective goal of improving the quality of biological implants, and I feel that we have a really great purpose as a collective. Nevertheless, it was brought to my attention that we are focusing on the cutting edge of technology which is mostly only available to those at the forefront of society.

The first things that came to my mind was the availability and access of hip replacements to those in the global south, with regards to hospitals, surgeons, equipment and money. This kind of disparity is even apparent in countries like the UK, with geographical inequality persisting in the north south divide in England [1].

So… what can we do to improve this? As early-stage researchers, I would enjoy an open discourse and increase the awareness of these issues, and maybe some of us could go on to make not just a difference in the medical field, but also aid those less fortunate than ourselves.


This article was written by Ben Clegg part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Ben is researching the Wear particle characterization and bio-compatibility of newly 3D printed self-lubricating polymer composites in total joint replacements at Luleå University of Technology, Sweden.





[1] Ryan-Ndegwa, S., Zamani, R. & Akrami, M. Assessing demographic access to hip replacement surgery in the United Kingdom: a systematic review

[2] Header Image:  – https://www.strategicmarketresearch.com/market-report/hip-replacement-implants-market



Recycling orthopedics, what happens after cremation?

In Sweden around 100,000 people pass away every year, and 70% of those are cremated [1]. Since 2016 it has been mandatory for the church to arrange recycling for any and all metallic components left after cremation.

Since then, 60 tons of metal has been recycled. It was calculated that a value of 250 Million dollars could be recouped per year if the Swedish numbers were extrapolated to the United states and Europe.

These metal parts are melted down back into ingots and can be repurposed into new materials. These normally cannot be re used as implant materials, due to increased chance of infection rate and if cremated have been chemically altered by the heat. But the high-grade titanium and cobalt ores can find there way into the aviation industry [2].

For future thoughts and discussion … What can we do with the implants that are not used and have been replaced the ever-advancing technologies and materials?


  1. Lidgren, L., Raina, D.B., Tägil, M. and Tanner, K.E., 2020. Recycling implants: a sustainable solution for musculoskeletal research. Acta Orthopaedica91(2), pp.125-125.
  2. https://www.theguardian.com/sustainable-business/2015/oct/06/metal-body-parts-hip-knee-replacements-cremation-circular-economy-recycling
  3. Header Image: https://ryortho.com/breaking/the-afterlife-of-cremated-orthopedic-implants/

This article was written by Ben Clegg part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Ben is researching the Wear particle characterization and bio-compatibility of newly 3D printed self-lubricating polymer composites in total joint replacements at Luleå University of Technology, Sweden.

The state of total Hip replacements in the developing world

Total hip arthroplasty is a fantastic operation that massively improve the patient’s quality of life. Most hospitals in the western world have access to state-of-the-art facilities which aid them with the surgery. In low-income countries, this access is limited. So how does it compare?

A study from Malawi [1] was chosen, as the first study to follow up on patients >10 years in a low-income country. The results are staggeringly positive and can even be compared to registries of high-income countries [2].

A 10-year mortality was at 20% (Malawi) vs 25% (UK) and a revision rate of 8% vs 5%. The Harris hip scores also compared rather favorably with high income countries. This is mainly attributed to the lower age of patients at an average of 52 years (Malawi) vs 68 (UK)

It should be noted that this was a relatively small study of only 70 patients, but one must bear in mind that only 3 hospitals in Malawi (a country with a population of 20 million) has the capability of performing a THA operation, and that patients live long distances from the hospital meaning they cannot afford the return journey.

Complications such as infection and dislocation are known as notable complications for this operation in low-income countries, but were not met in this study.
I think that this study reflects how well we can service people in need even in the poorest of conditions, and makes us think what good we could do by aiding countries like Malawi to improve their medical infrastructure.



[1] Graham SM, Howard N, Moffat C, Lubega N, Mkandawire N, Harrison WJ. Total Hip Arthroplasty in a Low-Income Country: Ten-Year Outcomes from the National Joint Registry of the Malawi Orthopaedic Association. JB JS Open Access. 2019
[2] National Joint Registry for England. Wales, Northern Island and Isle of Man. 14th annual report


This article was written by Ben Clegg part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Ben is researching the Wear particle characterization and bio-compatibility of newly 3D printed self-lubricating polymer composites in total joint replacements at Luleå University of Technology, Sweden.

Willy Wonka – an eminent biotribologist?

Researchers at the University of Leeds, Dr Siavash Soltanahmadi, Prof Michael Bryant and Prof Anwesha Sarkar based at the School of Food Science have looked into why the melt in the mouth taste of chocolate is so irresistable.

The paper Insights into the Multiscale Lubrication Mechanism of Edible Phase Change Materials investigates the lubrication behaviour of phase change materials (chocolate being one of many) from an oral tribology context.

During mastication, a phase change often occurs in a sequence of dynamic interactions between the ingested phase change materials and oral surfaces from a licking stage to a saliva-mixed stage at contact scales spanning micro- (cellular), meso- (papillae), and macroscales. Often the lubrication performance and correlations across length scales and different stages remain poorly understood due to the lack of testing setups mimicking real human tissues.

Unprecedented results from this study supported by transcending lubrication theories reveal how the tribological mechanism in licking shifted from solid fat-dominated lubrication (saliva-poor regime) to aqueous lubrication (saliva-dominant regime), the latter resulted in increasing the coefficient of friction by at least threefold. At the mesoscale, the governing mechanisms were bridging of cocoa butter in between confined cocoa particles and fat coalescence of emulsion droplets for the molten and saliva-mixed states, respectively.

Prof Anwesha Sarkar, from the School of Food Science and Nutrition at Leeds, said it is the “location of the fat in the make-up of the chocolate which matters in each stage of lubrication, and that has been rarely researched”. [BBC News]

Dr Soltanahmadi said: “Our research opens the possibility that manufacturers can intelligently design dark chocolate to reduce the overall fat content.” [BBC News]

This paper garnered significant public interest with articles quickly published in The Guardian and BBC News as well as many many other media outlets.

The broader context of this work paves the way for new types of low fat food that optimise the mouth-feel (enabled via oral tribology insights) which may help users lose weight without comprimising food perception and taste!

Xolography: No time for layers in medicine and healthcare

With the introduction of the new volumetric 3D printing technique known as Xolography[1], the conventional approach of layer-by-layer printing in additive manufacturing is altered. To harden the resin, it uses two different types of wavelengths and various initiators. In comparison to conventional photopolymerization techniques, this speeds up the process and produces a smoother surface with more material options.

A new company using this technology, Xolo3D, has published a paper in nature [1]. The brief video about this technology is available here Xolography. See the header image which shows The Xcube: Volumetric 3D printer and new photoinitiator from Xolo3D [1].

How it is different from the other 3D photopolymerization techniques?

Xolography is a dual color volumertric 3D printing process and uses the light to cure the photoresin similar to the SLA/DLP printers. However, Xolography employs the novel kind of initiator. When the single wavelength light strikes this initiator, the curing process does not begin. It takes two wavelengths of light (blue and red) to start photopolymerization, and the initiator cures wherever the two wavelengths of light meet.

This has some limitations as well:
⦁ Transparent resins are required (as printing zone is bigger and avoidance of absorption of light is necessary)
⦁ Highly viscous resins (in order to prevent from sinking after they have been printed and to avoid any kind of support structures)

This innovative technology makes printing faster, smoother (no polishing is necessary), and more material possibilities. This technology, specifically bioprinting techniques like printing high-resolution hydrogels, has enormous potential in the medical field.

More interested readers are guided to the nature paper and webinar from the R &D manager of Xolo3D. Webinar by Niklas König



[1] Regehly M, Garmshausen Y, Reuter M, König NF, Israel E, Kelly DP, Chou CY, Koch K, Asfari B, Hecht S. Xolography for linear volumetric 3D printing. Nature. 2020 Dec;588(7839):620-624. doi: 10.1038/s41586-020-3029-7. Epub 2020 Dec 23. PMID: 33361791.


This article was written by Dilesh Raj Shrestha as part of an ongoing series of scientific communications written and curated by BioTrib’s Early Stage Researchers.

Dilesh is researching the Development of 3D-printable, self-lubricated polymer composites with improved wear resistance for total joint replacement at Luleå University of Technology, Sweden.