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.



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:  –



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.
  3. Header Image:

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.

Can ChatGPT help develop medical devices?

Open AI, an artificial intelligence R&D company, recently launched ChatGPT, an AI based on an optimized language model to interact with humans in a conversational manner. As mentioned on Open AI’s website, once a user has created an online profile, it becomes possible to engage in a dialogue with ChatGPT, which is capable of answering follow-up questions, admitting mistakes, challenging incorrect premises and rejecting inappropriate requests.

For example, when ChatGPT is asked “How can AI improve 3D printing?” and then “Do you have more specific examples for 3D printing in medical applications?” the AI is able to instantly give the answers visible in the image. The AI gathers information to provide relevant insight into possible medical application areas where AI could help humans optimize the current 3D printing process. This dialogue system represents an excellent opportunity to realize the full potential of AI by saving time collecting information and compiling it into written text, although reference checking remains essential.


Asking AI (ChatGPT) how AI can improve 3D printing in medical device applications

Open AI’s goal is “to make AI systems more natural and safer to interact with” by using ChatGPT to receive user feedback. Since ChatGPT is capable of answering questions and writing a text on a topic resulting from the collection of information available online, it can be used by students, teachers or scientists for writing purposes. The increasing accessibility and performance of AI will challenge areas that include writing, such as education (homework) or science (publication introductions). Managing the integration of AI into our work processes and setting its limits will likely lead to interesting discussions about the balance between benefits and drawbacks.


Learn more about OpenAI and use ChatGPT here.


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.

A guide to in vitro testing

Sometimes, designing a suitable in vitro protocol is not an easy task and every biologist knows it. The two most important aspects when you design an experiment are: the research question and the model that you want to use to represent the reality. In my opinion, finding the research question is definitely hard, but not the hardest part. The most difficult part is when you want to artificially reproduce an entire micro/macro-environment in a cell lab. The preferred method would be to just skip complex in vitro testing and go directly in vivo but we, as scientists, are committed to respecting life, including animal life. This is why we spend much of our time and resources developing new methodologies to test different aspect of many biological mechanisms.

The first thing to do when you are trying to develop a good in vitro model is breaking the problem in small little bricks and then analyze them separately. Most of the time you cannot include a lot of parameters at the same time in a single test. Then, one is left with a lot of variables and decisions to set and modify to mimic the real test environment. This could be tricky since nowadays we have a lot of options to choose when you talk about cell culturing. There are a lot of products in the market that could be used for your experiments. This is of course good news, but sometimes this could also be quite confusing. It is not rare that a colleague contacts me to seek advice about cells, media, supplements and so forth.

The good news is that there are a lot of papers that helps other researchers in picking the right methodology, test or products that best suits their needs. Typical in vitro testing problems can be: selecting the right cell line or primary cells, choosing the right culture media both to keep the cells healthy and to mimic the natural environment as closely as possible. Moreover, all of this must obviously meet reality! Everything is feasible on paper, but the transition from a piece of paper to the cell lab is too complex to be imagined in its entirety in advance.

My tips and tricks to create successful in vitro protocol are few and perhaps well-known but maybe they could help someone to find again the right perspective about this. First of all, plan as much as you can but do not skip lab work. This is so important! Always put yourself out there so you will face real problems and you will take real decisions to get rid of them. Secondly, be loyal to your research question and make decisions based only on that. Lastly, while you work with “standard” or “well established” methods always try to improve them. Try to push things to the limit, but don’t try something just because it’s new. Try it only if it makes scientific sense!


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

Niccoló is researching Bioimaging of biomaterials and biological characterization of 3D-printed alloys for reconstructive surgery at Uppsala University, Sweden.


3D Bioprinted Implants for Critical Size Bone Defects

Header Image: Scheme (A) and image (B) of the FRESH process showing the gel of interest (A. green, B. black) printed in the temporary support gel. After printing layer by layer, the 3D structure is released by melting the support gel.

A critical size bone defect is defined as the absence of a bone segment that would not heal spontaneously and require surgical intervention to make the bone functional again. The exact size and volume of a critical size bone defect depend on the patient and the location, but in most cases refers to a defect that is greater than 1 cm in length and greater than 50% of the circumference of the bone in volume. Critical size bone defects are the result of pathologies or traumatisms such as infections, tumor resections, non-union fractures or accidents and lead to a difficult clinical scenario for the surgeon and the patient. As the bone is not able to insure bone regeneration to fill the gap, several surgical procedures promoting osteogenesis (bone formation) are currently used like the Induced Membrane Technique, Distraction Osteogenesis and autologous (from the patient) grafting. These procedures present several limitations such as multiple surgical interventions, infection, long duration of reconstruction, donor site morbidity. There is an un-meet clinical need for scaffolds supporting bone formation and viable osteointegration in a cost-effective manner while minimizing patient morbidity (complications). 3D printed implants represent a promising alternative currently under investigation in the orthopaedic research field [1].

Within the ETN BioTrib working on orthopaedic implant technology, some projects aim at making progress towards the development of biodegradable scaffolds specific to patients’ bone defects. 3D bioprinting according to a design following the complex internal architecture of bone with collagen (main bone component) and autologous cells would combine interesting features to support bone regeneration while the implant is degraded. However, reaching mechanically stable scaffolds (not collapsing or deforming under their own weight) over several millimeters with good resolution can be hard when printing superimposed layer of soft gels. The emerging FRESH (Freeform Reversible Embedding of Suspended Hydrogels) bioprinting technology, first described in 2015 by Dr. Feinberg’s group, represents a promising approach to overcome this limitation, as collagen is printed into a secondary gel used as a temporary support.

The main advantage is to maintain the intended 3D geometry using biologically relevant soft gels that would collapse if printed in air. Once the 3D structure is FRESH printed, the support gel is discarded through melting while maintaining the stability and resolution of the collagen 3D structure. FRESH scaffolds present limitations encountered in 3D bioprinted scaffolds, namely vascularization of thick scaffolds, and ability to resist loading which is needed for bone implants. FRESH bioprinting of functional implant for critical size bone defects requires further development, but this technology expands the bioprinting possibilities in academia and industry [2].

[1] Mayfield, C. K., Ayad, M., Lechtholz-Zey, E., Chen, Y., & Lieberman, J. R. (2022). 3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions. Bioengineering, 9(11), 680.
[2] Hinton, T. J., Jallerat, Q., Palchesko, R. N., Park, J. H., Grodzicki, M. S., Shue, H. J., Ramadan, M. H., Hudson, A. R., & Feinberg, A. W. (2015). Three-dimensional printing of complex biological structures by freeform reversible embedding of suspended hydrogels. Science Advances, 1(9).


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.

BioTrib: External Expert Advisory Board Meeting

Great recent External Expert Advisory Board meeting for BioTrib!

Early Stage Researchers provided an overview of the progression in each of the work packages and their own career development.

Erudite conversations, succinct presentations and insightful recommendations from the board. Special thanks to the external advisory members including the Chair, Dr Vishal Borse, Jude Meakin, Sara Manzano, Heather Yates and Lars-Erik Rannar.

Header Image: A sample of the BioTrib personnel present at the EEAB.

Additive Manufacturing in Medical Applications

Additive Manufacturing (AM) is the process of creating an object by building it one layer at a time. It is a sustainable production method that eliminates the need for excess material and unnecessary waste. It can be used to fabricate complex shapes without tooling. The cost of manufacturing with AM is often not cheaper than conventional processing, particularly if the product is designed for mass production. AM processes include VAT photopolymerization, material jetting, material extrusion, binder jetting, powder bed fusion, sheet lamination, and directed energy deposition. These AM processes are briefly explained as follows:

  • VAT photopolymerization: liquid photopolymer in a vat is cured by light, and the material form is liquid.
  • Material jetting: droplets of material are selectively deposited, and the material form is liquid.
  • Material extrusion: material is dispensed through a nozzle in layers, and the material forms are filament, pellets, and paste.
  • Binder jetting: a liquid bonding agent is selectively deposited, and the material form is powder.
  • Powder bed fusion: thermal energy fuses regions of a powder bed, and the material form is powder.
  • Sheet lamination: sheets of material are bonded to form an object, and the material form is sheets.
  • Directed energy deposition: focused thermal energy fuses materials as deposited, and the material forms are powder and wire.

The medical applications of AM are classified as follows:

  1. Medical models: Medical models are based on patient anatomy, and they can be used for preoperative as well as postoperative planning. They are widely used in the craniomaxillofacial area, also for limbs, the spine, and the pelvis. Powder bed fusion, material extrusion, and binder jetting are three AM processes that are usually utilized for medical models.
  2. Implants: Implants are manufactured directly or indirectly by AM to replace damaged or missing tissue. AM is a favorable choice for manufacturing personalized implants. Most of the implants are constructed from metals using the powder bed fusion process. In some cases, polymers and ceramics are utilized to fabricate the implants.
  3. Tools, instruments, and parts for medical devices: Tools, instruments, and parts for medical devices improve clinical operations. Patient-specific dimensions and shapes might be used. Surgical instruments as well as orthodontic appliances can be considered in this classification. The VAT photopolymerization process is often employed to manufacture tools, instruments, and parts for medical devices.
  4. Medical aids, supportive guides, splints, and prostheses: Parts created with AM are external to the body and can be customized. Long-term and postoperative supports, motion guides, fixators, external prostheses, prosthesis sockets, and personalized splints can be taken as examples of this category.
  5. Biomanufacturing: A combination of AM and tissue engineering is considered Biomanufacturing which mostly uses polymers, ceramics, and composites. Porous structures are also utilized that are favorable to attracting cells and cell growth.


[1] Salmi, Mika. “Additive manufacturing processes in medical applications.” Materials 14.1 (2021): 191.


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

Mahdieh is researching the Design of Self Lubricating Prothesis at ETH Zurich, Switzerland.

Aircrafts and Medicine: an unexpected connection

Sometimes unexpected events occur at unexpected times, providing inspiration for medicine. In this instance, it pertains to ophthalmology, more specifically intraocular lenses, and it occurred during World War II. Intraocular Lenses (IOLs) are optical lenses that can correct refractive defects by being implanted in the eye. IOL-based cataract surgeries are currently one of the most popular and safest surgical procedures performed globally. (Yu, 2018)

The Second World War did, in fact, mark the genuine commencement of the IOL. Harold Ridley was a civilian ophthalmologist, who were operating on Royal Air Force pilots who suffered eye injuries, engaged in aerial combat over the South of England. On August 15, 1940, he underwent 19 surgeries on a pilot, whose Perspex canopy had shattered, sending numerous splinters of poly(methyl methacrylate) (PMMA, Figure 1) into his eyes.

Figure 1. (a) MMA (methyl methacrylate) forms the basis for acrylic IOLs. (b) (PMMA) is a transparent thermoplastic.

He discovered that the PMMA splinters, unlike glass splinters, remained inert in the patient’s eye and that the immune system had not responded to them during the course of the treatment. Ridley came to the realisation that PMMA could be utilised to create artificial lenses that could be inserted into the eye to replace the natural lenses that had been removed during cataract surgery. (Kretz, 2014)

He then, together with the Rayner Optical Company, produced the first IOL (Figure 2) adopting ICI’s Transpex I, a high quality version of PMMA. On November 29, 1949, at St Thomas’ Hospital, London, Ridley performed surgery inserting the first lens into a 42-year-old woman after an extracapsular cataract excision. (Scholtz, 2006)

Figure 2. Scanning electron micrograph of a Ridley intraocular lens made from PMMA

Today, millions of people’s lives have been made better thanks to Ridley’s brilliance. IOLs are now widely used for refractive outcomes improvement throughout clear lens exchange, not just during cataract surgery. The quality of vision following cataract surgery has never been greater in the developed world thanks to the incremental advancements in IOL design.

Take-Home Message: always keep an open mind, you never know where the next important medical discovery might come from!



Yu, N. F. (2018). State of the art of intraocular lens manufacturing. The International Journal of Advanced Manufacturing Technology, 1103–1130.

Scholtz, S. (2006, September). An Ophthalmic Success Story: The History of IOL Materials. From CRSTEurope:

Kretz, F. S. (2014, May 19). A Brief History of IOL Materials. From


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

She is studying a PhD in Tribological Characteristics of Nanofibrous Electrospun Materials at ETH Zurich.