Identification number: Nr.1.1.1.1/21/A/050

Type: ERDF

Project duration: 01.01.2022 - 30.11.2023

Project manager: Dr.hab.phys. Juris Purāns

Partners:

  • Latvian Biomedical Research and Study Centre (LBMC)
  • SIA SIDRABE Vacuum

Total funding:

The total budget is 500 000 EUR with ERAF contribution of 425 000 EUR.

Project aim:

The aim of this industrial research project is to develop advanced roll-to-roll (hereinafter R2R) physical vapour deposition (PVD) technology for large scale production of a new type of multifunctional antibacterial and antiviral (MABAV) coatings. We propose to produce and investigate MABAV materials in the form of thin films and multilayers with photochromic and transparent conducting multifunctionalities based on rare-earth oxy-hydrides (REHO) and metal oxides (MO) in combination with the metal and other dopants.

Project summary:

COVID-19 pandemic calls for new ways to combat pathogen resistance. The pathogens can persist on several types of surfaces long enough causing transmission of various infectious diseases [1], which are a continuous threat to human health and have a negative impact on the economy. The hospital environment is the epicentre of most antibiotic-resistant infections, especially respiratory pathogens, and where outbreaks occur. According to the European Centre for Disease Prevention and Control, more than four million people are estimated to acquire a healthcare-associated infection (HCAI) every year in Europe [2]. In addition, antimicrobial resistance towards antibiotics is growing everyday due to environmental changes and microbial adaptation abilities. For these reasons, the development of advanced solutions is urgently needed today. The knowledge on the survival of bacteria, fungi, viruses, and protozoa on surfaces, and hence, in a broader sense, in the human environment, is important for planning and implementing tactics for prevention of HCAI [3].

Within the framework of this industrial research project an advanced roll-to-roll (hereinafter R2R) physical vapour deposition (PVD) technology for large scale production of a new type of multifunctional antibacterial and antiviral (MABAV) coatings will be developed. MABAV materials in the form of thin films and multilayers with photochromic and transparent conducting multifunctionalities based on rare-earth oxy-hydrides (REHO) and metal oxides (MO) in combination with the metal and other dopants will be produced and investigatd.

Applications: smart windows/glass, smart foils/sheets (as partitions and barriers in public places) and transparent electronics applications, including medical devices, with the aim to prevent the diseases in terms of reduction of bacteria and virus prevalence with attention to the SARS-CoV-2 to limit and reduce the spread of this virus and consequently caused illness COVID-19.

This project will be implemented by the Institute of Solid State Physics of University of Latvia (ISSP UL), a vacuum coating SME company SIDRABE Vacuum Ltd (SIDRABE) and Latvian Biomedical Research and Study Centre (LBMC). This interdisciplinary project consists of the research activities in Physical (1.3), Chemical (1.4) and Biological (1.6) sciences, and Materials engineering (2.5).

[1] Journal of Hospital Infection 99 (2018) 239-249.
[2] European Centre for Disease Prevention and Control. Point prevalence survey of healthcare-associated infections and antimicrobial use in European acute care hospitals 2011–2012. Stockholm: ECDC; 2013.
[3] Coatings 9 (2019) 654.

Expected scientific results:

  • Novel R2R deposition technology of MABAV coatings on flexible substrate (results: new technology, patent);
  • Novel REHO and MO thin films and multilayers with advanced MABAV properties (results: scientific articles, new product prototype, patent).
 
 

Project progress information

Par periodu: 01.07.2022.- 30.09.2022. | September 30, 2022

Performed activities.

ISSP:

Deposition of new WO3/Cu/WO3 samples continued (still ongoing) with the main goal of studying the stability of the coatings. The coatings are deposited on previously specially prepared glass substrates with electrical contacts, in order to be able to measure the electrical conductivity over a longer period of time and to determine the effect of deposition parameters. In addition, the optical properties of these samples are regularly measured by spectral ellipsometry. Both electrical and optical properties are observed to vary with time and correlate with deposition parameters. Manufacturing parameters have been found that guarantee stable films whose physical properties do not change over time. The next steps in the research include determining the physical processes that cause the instability of the described properties. X-ray diffraction, deep modeling of ellipsometry data, Raman and infrared spectroscopy and other techniques will be used for this purpose. The results will provide additional knowledge for the interpretation of antimicrobial activity and for fabricating stable coatings.

 

SIDRABE:

During the past research period the functionality of the roll-to-roll (R2R) equipment was expanded and large-area PET/WO3/Cu/WO3 samples production has been started.

  • A linear actuator with a movable screen was designed, manufactured and placed in the sample production plant to ensure the creation of metallic Cu contacts on the sides of the samples.
  • Calibration of the equipment was carried out, determining the thickness of the WO3 layer depending on the oxygen flow, for the production of a new series of PET/WO3/Cu/WO3 large-size samples according to the specification submitted by the partners.
  • The production of the new series of samples has been started.
   

LBMC:

Testing activities for anti-bacterial and anti-viral effects include a wide range of testing methodologies and techniques. Performed activity is not limited to the implementation of traditionally used testing methodologies. The methodologies described in the testing standards were adapted to the optimal number of tested samples in their more suitable sizes. Optimizations led to more effective usage of samples and increased overall accuracy of the experiments. The optimized methodology has been approved on several bacterial species and supplemented with methods for determining anti-viral effects. Molecular testing methodologies are used in order to better understand the mechanisms of action of the tested anti-microbial coatings on microorganisms. Changes in the enzymatic activity of bacteria and the production of reactive oxygen species compounds in contact with the coating surface are determined. The experimental work with a wild-type SARS-CoV2 virus (lineage B1.1.7) has been started at BSL3 biosafety laboratory. The methodology for virus cultivation and testing on the PET surface will be developed.


Par periodu: 01.04.2022.- 30.06.2022. | June 30, 2022

Performed activities at ISSP:

1. A new set of multilayer (WO3/Cu, WO3/Cu/WO3, WO3/Cu/W/WO3, ZnO/Cu/ZnO) coatings was prepared on glass substrate with the goal to improve electrical conductivity, optical transparency and antiviral and antibacterial properties by varying the thickness of individual layers.

2. Spectroscopic ellipsometry measurements revealed:

  • Glass/Cu and Glass/WO3 films are homogeneous
    • Optical properties of Cu and WO3 are comparable with the data base, however resistivity of Cu is of one order lower (3.1×10-5 W×cm) respect to the reference data (5.4×10-6 W×cm);
    • No variation of refractive index and extinction coefficient was observed within the depth of the films;
    • Obtained thickness of the Cu and WO3 films coincide with the planned values during deposition.
  • Glass/WO3/Cu and Glass/WO3/Cu/WO3 films are inhomogeneous:
    • Variation of refractive index and extinction coefficient was observed within the depth of the films due to the Cu diffusion in both WO3 layers;
    • The second layer of WO3 (on Cu) is thinner compared to single WO3 on glass: it is possible that the growth of WO3 on Cu is slower.

3. Electrical resistance of Cu was measured during the deposition of the Glass/Cu/WO3 sample. The value obtained indicates the formation of metallic Cu and is constant during the deposition of the WO3 film. We conclude that no significant oxidation of Cu occurs during the sample preparation process.

 

In parallel, SIDRABE continued the preparation of R2R equipment for the application of large-area antiviral and antibacterial coatings on PET substrates:

1. Drying of PET substrate has been realized in the R2R device.

2. The supply of gases required for magnetron sputtering processes has been realized.

3. The operation of the R2R device in the:

  • Metallic mode of Cu and W coatings (Ar atmosphere) has been established.
  • Tungsten oxide (WO3) sputtering mode (Ar and O2 atmosphere) has been established.

4. The R2R equipment was calibrated for the thicknesses of the metallic and oxide layers depending on the amount of oxygen supplied to the process, the power of the magnetrons and the pressure in the chamber.

5. The first series of 8 pilot samples has been produced and submitted to the project partners for characterization to further optimize the parameters of coating production.

 

LBMC analysed antimicrobial properties for a set of ZnO and Cu nanocoatings using two types of bacteria, including Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus:

  1. ZnO and ZnOCuZnO coatings did not show a significant antibacterial effect.
  2. Cu coated PET samples showed antibacterial activity:
  • When analyzing the viability properties of bacterial cells (MTT test), it was found that copper coatings reduce the viability of cells in both cultures.
  • The amount of reactive oxygen species (ROS) was measured by cultivating cells on different coatings. As a result, only copper showed an active type of oxygen on the surface, causing a significant antibacterial effect.
  • Similar results were obtained in virus experiments using MS2 bacteriophage and replication defective human SFV virus, where only Cu-coated PET samples showed statistically significant antiviral effects.
  1. When comparing two bacterial cultures, S. aureus showed a much higher degree of inhibition than E. coli, respectively.
  2. Innovative digital PCR quantification method was used to determine the SFV virus titre, which was presented at FEBS3+ conference, 16.06 - 18.06.2022, Tallinn, Estonia. The title of the poster presented was “Quantification of alphaviral vectors using droplet digital PCR”, autors: Ksenija Korotkaja and Anna Zajakina.

Period: 01.01.2022.- 31.03.2022. | March 31, 2022

At the beginning of the project, ISSP prepared the thin-film magnetron sputtering equipment, compiled the procurement list of the required metallic and alloyed targets, and did first characterization of the fabricated coatings:

Optimization of magnetron sputtering process, preparation of first single-layer (Cu, ZnO, WO) and multilayer (WO3/ Cu/WO3, WO3/Cu/W/WO3, ZnO/W ZnO) coatings.

  1. A list of targets to be obtained for the development of innovative single-layer and multi-layer MABAV coatings on glass and plastic sheets has been established:
    • Gold (Au) wire, 1 gram, 99.99% purity, 1.0 mm diameter
    • Silver (Ag) wire, 1 foot, 99.99% purity, 1.5 mm diameter
  2. UV-VIS-IR spectroscopic measurements of transparent conductive thin films to determine the reflectance, transmission and absorption spectra of the films.
  3. Spectroscopic ellipsometry measurements of transparent conductive thin films to evaluate film thickness and quality (dispersion curves of optical constants, band gap, optical gradient, surface roughness).

SIDRABE has adapted the roll-to-roll (R2R) equipment for the sputtering of the thin films required in the project:

  1. Tightness and necessary high vacuum condition of the sputtering chamber have been checked, and found shortcomings have been rectified.
  2. Magnetron cooling system was cleaned and checked for leaks.
  3. Conditioning of the film winding system has been made and stability improved.
  4. W and Cu magnetrons have been installed to allow the first coatings to be formed in the pilot mode.

To evaluate the antiviral and antibacterial properties of novel nanocoatings  the testing methodology was established according to EN ISO 1276 and EN ISO 16615 and approved by LBMC on the first samples obtained from ISSP:

  1. Currently, the protocol is optimised for gram-negative and gram-positive bacteria cultivation: Escherichia coli, Staphylococcus aureus.
  2. Preliminary data on biocidal activity of tungsten oxide containing nanocoatings have been obtained.
  3. Furthermore, to evaluate the antiviral activity of nanocoatings, several model viruses have been selected: Semliki forest virus (mammalian enveloped RNA virus), MS2 bacteriophage (RNA non-enveloped virus), Pf1 bacteriophage (circular single-stranded DNA filamentous virus). The respective viruses were produced and quantified.