Physical validation of an in-silico designed alloy for bioengineering applications

We have worked with Alloyed Ltd to design and validate alloys meant to be strong contenders as candidates for making orthopaedic and medical devices.

There are three aspects that we consider when we study alloys in the MMM Lab: their physical and mechanical performance, their chemistry, and their biological behaviour (once the alloys are exposed to living cells, esp. those that are meant to form bone).

This multiobjective optimisation revealed a very interesting candidate:

There was an alloy that climbed to the top of our shortlisting, and the combination of alloying elements has also attracted much interest from the scientific community: a Titanium alloy containing TiNbTaZrMoSn elements. This alloy is attractive because it does not contain toxic elements (such as Al, V or Ni), and is meant to be a beta-stabilised alloy, which means that its stiffness is lower than that of pure Titanium and therefore closer to that of bone.

In the first instance Alloyed Ltd used computational methods to predict which combination of those elements, and in which quantities, would render the optimum alloy with regards to stiffness, strength, transition temperature and biocompatibility. The selected alloy was then realised in our Multifunctional Materials Lab and tested for physical, mechanical, chemical and biological performance. The experimental results were then compared to the predictions we had for this designed alloy.

While the thermomechanical computational predictions matched reality well, the biological behaviour results were way off.

It looks as if the body of work that has led to models and numerical calculations of the metallurgical phase, the mechanical properties and the transition temperatures have reached maturity. However, this is not the case for the biological prediction models of biocompatibility and osteoblastogenesis (i.e., how fast and well cells commit to becoming a bone-forming cell). These models are still too simplistic and we will have to consider more aspects of the cell/surface/bulk interaction to make them faithful to what is going on in reality. In this way we will be able to run in-silico predictions which will yield trustworthy results. This would be game-changing, as we will be able to accelerate the design & manufacture & deployment cycle that medical devices require to achieve better products to help heal faster and long-term. For example, tailoring materials to the patient to fulfil their personalised needs.

This work has been published in the Journal of the Mechanical Behavior of Biomedical Materials and can be read here: https://doi.org/10.1016/j.jmbbm.2021.104858…

This is a first step towards a complete model of cyber mechano-biological properties. The work continues in the MMM Lab. https://doi.org/10.1016/j.jmbbm.2021.104858

WHICH 3D PRINTED STRUCTURE IS MOST CELL FRIENDLY?

Orthopedics This Week (OTW) has reported on our study of topology to improve osteogenesis in load-bearing implants.

They interviewed us and quoted this extract from that interview as follows:

Dr. Torres-Sanchez told OTW, “Although we are all different in terms of anatomy and physiological needs …in the ways we age, exercise, and live, medicine/technology that feeds into medical devices has largely been a one-size-fits-all approach. My 82-year-old neighbor has a very different lifestyle different from my 57-year-old neighbor who bikes 10 miles a day. If both individuals are in an accident and need an orthopedic device, they will need different products. With personalized medicine we have improved chances of producing long lasting orthopedic devices that allow cells to move in and create a mineral material that makes up our bone and carries no risk for infection.”

https://ryortho.com/breaking/which-3d-printed-structure-is-most-cell-friendly/

The full interview can be read here.

The study that this interview is referring to can be found here. The sponsors are EPSRC/UKRI and our inductrial partners are Alloyed Ltd and Core Specialist Services Ltd.

Magnetic Fields to Aid the Manufacturing of hi-performing Composites

Bradley Mee has spent his Wolfson bursary in our lab developing a novel method to align reinforcing fibres within a polymeric matrix using magnetic fields. In this way, the mechanical properties of the composites can be tailored for specific applications and load requirements.

In his final report he wrote:

“Polyurethane composites are widely used due to their strength and light weight-ness, as well as the low cost and scalability in production. The PU material comes in two separate liquid chemicals that once combined in equal amounts rapidly expand to 200% of the original volume and cure hard, taking the shape of the mould it is placed in. There is an opportunity to shape and further increase the strength of these parts by forming a composite of PU and carbon fibres (added in the liquid/expanding stage), with localised reinforcements. It has previously been shown that these composite materials produced increase stiffness in both tensile and compressive testing.

The aim of the project is to test the hypothesis that [a magnetic field] aids the alignment of carbon fibres in a certain direction and will increase the strength of the material, compared to randomly located fibres. To achieve this; firstly, a literature review of electromagnetism and permanent magnets was carried out. Secondly, finite-element software was used in order to create a model of the problem and to visualise the magnetic fields created by the magnets. These two objectives provided the basis for a prediction on the direction and alignment that magnetised carbon fibres. Thirdly, lab-based experiments were carried out using a magnetometer to measure the actual magnetic field strength in air. The results were compared to those of the computer model and confirmed to be congruent. Finally, composites were produced in a bespoke mould and the specimens underwent mechanical testing.”

Bradley in the lab during sample production

Bradley has returned to his Electrical and Electronics Engineering studies and is aiming to pursue a career in the aerospace where these high performing composites could be in use in the near future.