Prof Carmen Torres-Sanchez

Published in Celebrating Excellence in Advanced Engineering Materials: Women in Engineering Materials: Advanced Engineering Materials (wiley.com)

Triply periodic minimal surface and trabecular-like structures are common approaches in tissue engineering. There are few comparative studies assessing the impact of topology on biological and mechanical performance independent of porosity and surface area. Herein, these two features are controlled, despite design-to-manufacture disparities intrinsic to selective laser melting. Smoothed trabecular scaffolds, with more accessible throats lined with microporosity, enhance osteoblastogenesis.

Published in the Journal of the Mechanical Behaviour of Biomedical Materials 124 (2021) 104858

Journal of the Mechanical Behavior of Biomedical Materials | ScienceDirect.com by Elsevier

Published in the Materials Letters Journal (Volume 343, 15 July, 134367)

Partially sintered satellite particles in scaffolds produced via Selective Laser Melting (SLM) create discrepancies between the as-designed and the as-manufactured properties (esp. porosity). These discrepancies impede direct comparison of manufactured parts performance to computer simulations. We propose anodic electrolysis using an electrolyte based on non-aqueous ethlylene-glycol TiCl4 (EthaTi) to remove the secondary roughness on titanium SLM-ed porous scaffolds. Post-processed gyroid scaffolds regained 10% porosity with respect to their as-manufactured value (65.20 ± 0.23%), which was close to the as-designed value (75.12%). Compared to other well-established electrolytes, this method is cost-effective, user-friendly and practical, as it requires shorter processing times, is temperature-stable and of gentler chemistry.

Published in the Biomaterials Advances Journal (Volume 153, October 2023, 213572)

Abstract

Data-enabled approaches that complement experimental testing offer new capabilities to investigate the interplay between chemical, physical and mechanical attributes of alloys and elucidate their effect on biological behaviours. Reported here, instead of physical causation, statistical correlations were used to study the factors responsible for the adhesion, proliferation and maturation of pre-osteoblasts MC3T3-E1 cultured on Titanium alloys. Eight alloys with varying wt% of Niobium, Zirconium, Tin and Tantalum (Ti— (2–22 wt%)Nb— (5–20 wt%)Zr— (0–18 wt%)Sn— (0–14 wt%)Ta) were designed to achieve exemplars of allotropes (incl., metastable-β, β + α′, α″). Following confirmation of their compositions (ICP, EDX) and their crystal structure (XRD, SEM), their compressive bulk properties were measured and their surface features characterised (XPS, SFE). Because these alloys are intended for the manufacture of implantable orthopaedic devices, the correlation focuses on the effect of surface properties on cellular behaviour. Physico-chemical attributes were paired to biological performance, and these highlight the positive interdependencies between oxide composition and proliferation (esp. Ti⁴⁺), and maturation (esp. Zr⁴⁺). The correlation reveals the negative effect of oxide thickness, esp. TiO_x and TaO_x on osteoblastogenesis. This study also shows that the characterisation of the chemical state and elemental electronic structure of the alloys’ surface is more predictive than physical properties, namely SFE and roughness.

Members of the RIED Loughborough attended the THERMEC 2023 Conference in Vienna, Austria, a very prestigious bi-annual International Conference on “PROCESSING & MANUFACTURING OF ADVANCED MATERIALS: Processing, Fabrication, Properties, Applications”

The work presented was on the biodegradable and bioresorbable materials for medical devices and scaffolds based on Ca-Mg-Zn chemistry for bulk metallic glasses. PhD researcher Shangmou Yang and supervisors Profs Paul Conway and Carmen Torres presented and defended the paper entitled “Can multifunctionality of bioresorbable BMGs be tuned by controlling crystallinity?” during the session ‘Metallic Glasses 3’ chaired by one of them most eminent and internationally respected experts in bulk metallic glasses, Prof Jürgen Eckert, from Montanuniversität Leoben & Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Leoben (Austria).

^{Shangmou presenting at THERMEC 2023}

It was Shangmou’s first international experience presenting his work; he was well prepared and did a very good job in front of scientists from all over the world who are also working on that alloy system. This work is co-sponsored by Alloyed Ltd, the Wolfson School of Mechanical, Electrical and Mechanical Engineering and EPSRC Programme Grant ‘RIED’.

^{Shangmou happy (and relieved!) after his presentation}

And to make it even more special…

The RIED-Wien local team came to support us and boost our mood!

We met with Dr Vincent McKenna, RIED alumnus, who now resides in Vienna. It was a fabulous occasion, and we spent a lovely time with him there, celebrating how well he is doing in the city he now calls home. We are already looking forward to meeting him again (here in the UK or in Wien!)

^{Shangmou, Vincent, Carmen and Paul at the Belvedere Palace gardens, in Vienna}

As published in Key Engineering Materials Volume 967

Ca-Mg-Zn bulk metallic glasses (BMGs) are promising biomaterials for orthopaedic applications because when they get reabsorbed, a retrieval surgery is not needed. In this study, Ca-Mg-Zn metallic glasses with different compositions, Ca_56.02Mg_20.26Zn_23.72 and Zn_50.72Mg_23.44Ca_25.84, were fabricated by induction melting followed by copper mould casting. Their degree of crystallinity was modified by annealing, obtaining exemplar specimens of fully amorphous, partially amorphous (i.e., a BMG composite (BMGC)) and fully crystalline alloys. The microstructure, thermodynamic and corrosion performance of these alloys were evaluated as well as their electrochemical behaviour. The results of polarisation tests demonstrate that the corrosion resistance of the Zn-rich alloy is markedly better than the Ca-rich BMG. Corrosion rates of these Ca-and Zn-rich alloys with different degrees of crystallinity illustrate that the corrosion behaviours of alloys strongly depend on their microstructure, which shows a positive correlation between the corrosion current density and the crystallised volume fraction of the alloy. This study aims to shed light on the impact of the amorphicity-to-crystallinity ratio on the multifunctional properties of BMGs/BMGCs, and to assess how feasible it is to fine-tune those properties by controlling the percentage of crystallinity.

This paper was presented at the June 2024 NAFEMs Conference. NAFEMS is the International Association for the Engineering Modelling, Analysis and Simulation Community.

Metallic scaffolds are used as implants to help heal bones. Sheet-based Triply
Periodic Minimal Surfaces (TPMS) are of interest due to their high surface-to-volume ratio (S/V), customisable stiffness, and can be realised using Additive Manufacturing (AM). Other studies investigate porosity and pore size of scaffolds but they frequently overlook S/V, which is critical for cellular response. Additionally, the limitation of AM (esp. Selective Laser Melting (SLM)) causes discrepancies between intended and actual physical and mechanical properties of those structures, and this also needs to be addressed. This work investigates three types of TPMS scaffolds made in pure Titanium, with an emphasis on design vs manufactured differences and the significance of S/V. As-designed scaffolds reported 70-75% porosity and 25-35 cm-1 S/V, and stiffness was measured using finite element analysis (FEA) at 6.7-9.3 GPa. The manufactured scaffolds had 59-70% porosity and 33-42 cm-1 S/V. Laboratory compression testing revealed an effective Young’s modulus of 5-9 GPa, comparable to bone. Image-based simulation method was also employed on the built samples which reported the stiffness range of 8.3-16.6 GPa, overestimating it by 57%. It is hypothesised that these discrepancies stem from the secondary roughness deposited on the scaffold walls during SLM, causing reduction in porosity yet not contributing to structure’s strength. The cyber physical validation methods presented are a good way to quantify these
discrepancies, allowing feedback to the design stages for more predictable as manufactured structures.

https://www.nafems.org/publications/resource_center/uk24_ext_abs_18

M. Khalil, M. Burton, S. Hickinbotham, P. P. Conway, C. Torres-Sanchez

Published in the Engineering Modelling Analysis & Simulation – The NAFEMS Journal Vol. 2, Issue 1, 2025

Abstract

Metallic scaffolds are used as implants to help heal bones. Sheet-based Triply Periodic Minimal Surfaces (TPMS) are of interest due to their high surface-to-volume ratio (S/V) and customisable stiffness. They can be realised using Additive Manufacturing. Other studies investigate porosity and pore size of scaffolds, but they frequently overlook S/V, which is critical for cellular response. Additionally, the limitation of AM (esp. Selective Laser Melting (SLM)) resides in the discrepancies between as-designed and as-built physical and mechanical properties of those structures, and this also needs addressing. This work investigates three types of pure Titanium TPMS scaffolds, with an emphasis on as-designed vs as-built discrepancies and the significance of S/V. As-designed scaffolds reported 70-75% porosity and 25-35 cm^-1 S/V, and stiffness was measured using finite element analysis (FEA) obtaining 6.7-9.3 GPa. The as-built scaffolds had 59-70% porosity and 33-42 cm^-1 S/V. Laboratory compression testing revealed an effective Young’s modulus of 5-9 GPa, comparable to bone tissue. Image-based simulation methods were employed on the as-built samples which reported the stiffness range of 8.3-15 GPa, overestimating it by 54%. It is hypothesised that these discrepancies stem from the secondary roughness on the surfaces, cracks and entrapped voids created during the SLM process, causing reduction in porosity, yet not contributing to structure’s strength. The cyber-physical validation methods presented in this work are a good way to quantify these discrepancies, allowing feedback to the design stages for more predictable as-built structures.

Shangmou Yang, Carmen Torres-Sanchez, Benoit Ter-Ovanessian, Paul P Conway

Published in the Journal of Alloys and Compounds, Volume 1010, 5 January 2025, 178081

Abstract

Bulk metallic glasses (BMGs) possess higher strength than crystalline alloys because crack propagation is halted through an amorphous structure without grain boundaries or crystal defects. Nanoinclusions can further enhance mechanical properties. Here we investigate how the formation of nanocrystals into a Ti_41.2Zr_10.6Cu_39.1Pd_9.1 BMG matrix via controlled annealing that leads to devitrification of the bulk microstructure, as well as chemical changes to the surface oxide layer, affects mechanical and biological performance. The BMG nanocrystalline composite (BMGC, 12.8 % crystallinity produced via annealing at 415 °C for 5 min, based on crystallisation kinetics studies) was compared to the fully amorphous BMG and the fully crystalline counterpart (annealed at 415 °C and 60 min). BMGC fracture strength (1374.6 MPa) was higher than that of the amorphous BMG (1303.1 MPa) and the fully crystalline specimen (644.4 MPa). Young’s moduli correlated negatively with the degree of crystallisation (78.3–66.2 GPa). The results from in vitro tests on MC3T3-E1 illustrate that the surface chemistry plays a crucial role enhancing osteoblastogenesis: the presence of Zr oxides, wettable surfaces and large values of polar component of Surface Free Energy due to the nanocrystals, and a thinner oxide layer with low concentrations of Cu_xO, positioned BMGC as the preferred substrate. Tailoring amorphicity-to-crystallinity ratio in a Ti-Zr-Cu-Pd BMG is a route to create multifunctional substrates.