High-Performance Biocompatible Ag-DLC Coatings - Precise and Localized Silver Doping Through Novel Helium Pulse Injections

Project Information

HePULSE

Grant agreement ID: 885534

DOI

10.3030/885534

Project closed

EC signature date 24 March 2020

Start date 15 February 2021

End date 14 February 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 224 933,76

EU contribution

€ 224 933,76

Coordinated by

UNIVERSITY OF NORTHUMBRIA AT NEWCASTLE
United Kingdom

Periodic Reporting for period 1 - HePULSE (High-Performance Biocompatible Ag-DLC Coatings - Precise and Localized Silver Doping Through Novel Helium Pulse Injections)

Reporting period: 2021-02-15 to 2023-02-14

Summary of the context and overall objectives of the project

Silver-doped DLC coatings (Ag-DLC) are gaining interest in the biomedical sector, particularly for medical implants as they boost biocompatibility, antimicrobial levels, resistance against biofouling, hemocompatibility, and growth inhibition of unwanted biological organisms. The addition of Ag to a DLC matrix reduces the intrinsic residual stresses of the DLC matrix and promotes toughness for better mechanical performance. A typically made Ag/DLC exhibits Ag nanoparticles embedded throughout the DLC matrix. The excess of Ag may pose cytotoxic effects to the human body and Ag-enriched DLC coating also loses mechanical performance due to increased ductility.

The problem is important to society in terms of individuals’ health, healthcare costs, and environmental concerns. The excess of Ag leached into the human body may increase cytotoxicity risks for an individual’s health. The compromised mechanical performance shortens the implant life. Revision surgery not only puts a financial burden on the medical system but also may not be suitable for every individual in the context of clinical conditions, especially focused groups like elderly people. The revision surgeries also increase environmental challenges as the cost and resources of medical waste management increase for safe handling and disposal of retired implants.

We have identified that Ag is essential for the early post-surgery phase, thus it would be highly beneficial to develop a coating where Ag is only doped ‘as required’, providing maximum biological performance without reducing DLC strength. Selective Ag doping in a DLC matrix is challenging through established physical vapour deposition techniques. Hence, the overall objective is to develop a novel DLC coating with precise and localized doping of Ag nanoparticles simultaneously doped in a one-step process using the sputtering method. The mechanical and biocompatibility performance of the new coating design is to be validated against typically made Ag/DLC coatings. Other objectives include the professional development of the individual fellow to transform him into an expert and future leader of high-performance surface coatings by receiving professional trainings and qualifications in the subject area.

The HePULSE project has successfully developed a new Ag/DLC as depicted in the image section, which is 63% harder, 21% more biocompatible, and uses a small amount of silver as low as 2 at.% when compared to typically deposited 17 at.% Ag/DLC coatings. The individual fellow received professional trainings, particularly from Advanced HE, UK and FOSTER, EU, attended the academic events and exhibitions on a subject area and achieved the teaching qualification as Fellow of Higher Education Academy, UK before securing a permanent role as a faculty member of a prestigious university in UK.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

There were a total of 7 work packages (WP) in HePulse project. The fellow received health and safety training, performed COSHH assessments, and gained instrument specific training for deposition and testing of Ag/DLC coatings in WP1. The WP2 contained modification and deposition of Ag/DLC coatings using sputtering systems made by Teer Coating Ltd UK and Moorefield Nanotechnology, UK. WP3 corresponds to the mechanical testing using a nanoindentation platform and WP4 covers biocompatibility and antimicrobial studies against L929 mouse fibroblast cells and methicillin-resistant Staphylococcus aureus strain. The WP5 is related to professional development workshops, trainings, industrial linkage, teaching and mentoring students, proposal writing, and secondment and WP 6 covers knowledge transfer and dissemination of project outcomes through journal publications, conferences, seminars etc. The WP7 covers continuous monitoring and review of project progress.

The new Ag/DLC coatings were made with sputtering and precise shutter control to embed Ag particles and correspondingly tested with TEM, FESEM, EDX, XRD, nanoindentation, absorbance, cell viability, and counting bacterial colonies. A series of typical Ag/DLC was made with doping of 17, 40 and 65 at.% Ag in DLC matrix for comparative study. The new Ag/DLC design made in this project suggests that a small amount of Ag i.e. ~ 2 at.% releases a similar amount of Ag ions as released by typically made Ag/DLC design with 17 at.% Ag concentration. Further, the new Ag/DLC coating using 2at.% Ag is 63% harder, 21% more biocompatible, and shows adequate antimicrobial features when compared to typically deposited 17 at.% Ag/DLC coatings. The project outcomes are disseminated through journal articles (1) Soft diamond-like carbon coatings with superior biocompatibility for medical applications, Ceramics International – published (2) Biomechanical Characteristics of Silver Enriched Diamond-like Carbon Coatings for Medical Applications, Journal of Alloys and Compounds – Revision submitted JALCOM-D-22-17359R1 (3) A New Design of Precision Silver Doped Diamond-Like Carbon Coating with Superior Bio-Mechanical Performance – submitted CARBON-S-23-01114, and (4) Multi-functional bioactive diamond-like carbon coatings for medical implants, Biomaterials – submitted jbmt63755. The project work is also disseminated through presentations at Northumbria University and international conferences (1) The Korean Society of Mechanical Engineers Annual Meeting 2022 - ICC JEJU, Jeju, Republic of Korea and (2) International Conference on Advances in Design, Materials and Manufacturing Technologies 2022, Hong Kong. The project data is available with Open Access and DOI identifiers at Northumbria University institutional repository powered by Figshare.

The fellow has received FOSTER EU Open Science, Advance HE Gender and Research Design trainings, attended CPD events by IET, IMechE, Surface Venture, and European Researchers Night, wrote outline proposals, mentored PhD students, performed teaching and learning activities, learned TEM and FIB experimentation during secondments at Durham University, networked with industrial partners such as IHI IONBOND AG, Switzerland, Teer Coating UK, Moorfiled Nanotechnology, UK and achieved FHEA teaching recognition.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

A new silver doped diamond-like coating (Ag/DLC) design is successfully developed within HePulse project time frame, funded through H2020 Marie Sklodowska-Curie programme. The new coating design is useful for the industrial community, particularly manufacturers of medical implants. The new designs use a lower amount of silver and deliver superior bio-mechanical performance than typically made Ag/DLC coatings. Beyond technological impacts, the new development will (1) lower the implants cost due to less use of Ag, making it more affordable; (2) less use of Ag will contribute towards developing a sustainable supply chain of precious Ag metal. Further, the new development will also yield environmental impacts (3). The lower Ag amount in the new Ag/DLC design will pose fewer toxic effects on green ecology and also the cost, time, and resources for circular processing of used, broken or retired implants will be reduced.

HePulse Image