Jyrki Mäkelä - Academia.edu (original) (raw)

Papers by Jyrki Mäkelä

TechConnect Briefs, May 22, 2016

In this work ultraviolet A (UVA) light controlled photocatalytic activity of TiO 2 nanoparticles ... more In this work ultraviolet A (UVA) light controlled photocatalytic activity of TiO 2 nanoparticles is utilized on paper, paperboard, and plastic films for controlled wetting and oxygen sensors for modified atmosphere packages (MAPs). A liquid flame spray (LFS) process is used for a large-area TiO 2 nanoparticle deposition on natural fibre based substrates such as paperboard that results in a superhydrophobic surface. Controlled wettability is achieved using an UVA light activation that converts the surface to hydrophilic whereas an oven heat treatment recovers the initial superhydrophobicity. On the other hand, a TiO 2 nanoparticles with methylene blue (MB) dye is used to detect the presence of oxygen in modified atmosphere packages. We believe that photocatalytically active surfaces with tailorable properties will find many applications in the near future, for example, with printed functional devices.

SN applied sciences, Nov 27, 2018

Silver nanoparticles deposited on surfaces can provide an antibacterial effect with potential use... more Silver nanoparticles deposited on surfaces can provide an antibacterial effect with potential uses in, for example, healthcare settings. However, release of nanoparticles and their potential exposure to the environment is of concern. The current work demonstrates a continuous synthesis that simultaneously deposits silver nanoparticles onto plastic coated paper surface by utilizing the liquid flame spray (LFS) aerosol process. Heat from LFS is used to soften the thermoplastic paper surface, which enables partial and full embedding of the nanoparticles, thereby improving adhesion. The embedding is confirmed with atomic force and scanning electron microscopy, and the deposited silver amounts are quantified with X-ray photoelectron spectroscopy. The results suggest that embedding was more effective in PE-coated paper samples due to the lower glass transition temperature when compared to PET-coated paper samples. The antibacterial properties of the surfaces against E. coli and S. aureus were maintained and confirmed with a previously developed 'Touch-Test Method'. The LFS process has the potential to be used for large-scale manufacturing of antibacterial surfaces with improved nanoparticle adhesion on appropriately chosen thermoplastic surfaces.

Thin Solid Films, 2018

Controlled time release and leaching of silver nanoparticles using a thin immobilizing layer of a... more Controlled time release and leaching of silver nanoparticles using a thin immobilizing layer of aluminum oxide. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Tsf(2017),

Thin Solid Films, Feb 1, 2019

Silver nanoparticles (NPs) are known to provide antimicrobial properties for surfaces. However, t... more Silver nanoparticles (NPs) are known to provide antimicrobial properties for surfaces. However, there are environmental concerns due to reports of toxicity after exposure to the environment during or after end-use. Immobilizing silver NPs to the surface of substrates could ensure that particles are readily available for antibacterial activity with limited environmental exposure. A plasma coating on top of silver NPs could improve the adhesion of NPs to a substrate, but it could also impede the release of silver NPs completely. Furthermore, silver has been shown to require direct contact to demonstrate antibacterial activity. This study demonstrates immobilization of silver NPs with plasma coating onto a surface while maintaining its antibacterial properties. Silver NPs are simultaneously synthesized and deposited onto a surface with liquid flame spray aerosol technique followed by hexamethyldisiloxane plasma coating to immobilize the NPs. Atomic force microscope scratch testing is used to demonstrate improved nanoparticle adhesion. Antibacterial activity against gram-negative Escherichia coli is maintained even for plasma coating thicknesses of 195 nm. NP adhesion to the surface is significantly improved. Gram-positive Staphylococcus aureus was found be resistant to all the plasma-coated samples. The results show promise of using plasma coating technology for limiting NP exposure to environment. Highlights:  Roll-to-roll synthesis of silver nanoparticles using Liquid flame spray  Plasma coating for improved nanoparticle adhesion to substrate  Antibacterial properties of silver nanoparticles across plasma layer  Limited environmental exposure of silver nanoparticle

Advances in Natural Sciences: Nanoscience and Nanotechnology, Mar 20, 2019

A liquid flame spray (LFS) nanoparticle deposition process was used to generate glass surfaces wi... more A liquid flame spray (LFS) nanoparticle deposition process was used to generate glass surfaces with silver (Ag) and titania (TiO2) nanoparticles for antibacterial activity against two common pathogenic bacteria causing community-associated and hospital-acquired infections, gram positive Staphylococcus aureus (S. aureus) and gram negative Escherichia coli (E. coli). All nanoparticle coatings increased antibacterial activity compared to a reference glass surface. The silver nanoparticle coatings showed the highest antibacterial activity with E. coli. On contrary, TiO2 nanoparticle coatings were found to have a higher antibacterial activity against S. aureus than E. coli. No significant differences in antibacterial activity were observed between the two used nanoparticle deposition amounts.

Nordic Pulp & Paper Research Journal, Dec 1, 2014

Wettability of a solid surface by a liquid plays an important role in several phenomena and appli... more Wettability of a solid surface by a liquid plays an important role in several phenomena and applications, for example in adhesion, printing, and coating. Especially, wetting of rough surfaces has attracted a considerable scientific interest in recent decades. Superhydrophobic surfaces, which possess extraordinary water repellency properties due to their low surface energy chemistry and specific nano-and microscale roughness, are of particular interest due to the great variety of potential applications ranging from selfcleaning surfaces to microfluidic devices. Here we examine functional superhydrophobic and superhydrophilic nanoparticle coatings fabricated by liquid flame spray (LFS) on cellulose-based substrate materials. The article is a review of earlier papers with some new results and conclusions added. LFS has proved itself straightforward and versatile one-step method to fabricate broad range of functional nanoparticle coatings on various substrate materials in an atmospheric roll-toroll process. It has established itself among the most potential candidates for large-scale production of superhydrophobic coatings on affordable cellulose-based substrates.

Applied Surface Science, Oct 1, 2017

Highlights  One-step flame synthesis of silver nanoparticles  Roll-to-roll production of antiba... more Highlights  One-step flame synthesis of silver nanoparticles  Roll-to-roll production of antibacterial paper  Novel flame synthesis for silver nanoparticle production  Dry synthesis of nanosilver without effluents  Antibacterial nanoparticles produced directly onto surface of paper

MRS Proceedings, 2015

Nanostructured coatings have been prepared on a flexible, moving paperboard using deposition of c... more Nanostructured coatings have been prepared on a flexible, moving paperboard using deposition of ca. 10-50-nm-sized titanium dioxide and silicon dioxide nanoparticles generated by a liquid flame spray process, directly above the paperboard, to achieve improved functional properties for the material. With moderately high production rate (~ g/min), the method is applicable for thin aerosol coating of large area surfaces. LFS-made nanocoating can be synthesized e.g. on paper, board or polymer film in roll-to-roll process. The degree of particle agglomeration is governed by both physicochemical properties of the particle material and residence time in aerosol phase prior to deposition. By adjusting the speed of the substrate, even heat sensitive materials can be coated. In this study, nanoparticles were deposited directly on a moving paperboard with line speeds 50-300 m/min. Functional properties of the nanocoating can be varied by changing nanoparticle material; e.g. TiO 2 and SiO 2 are used for changing the surface wetting properties. If the liquid precursors are dissolved in one solution, synthesis of multi component nanoparticle coatings is possible in a one phase process. Here, we present analysis of the properties of LFS-fabricated nanocoatings on paperboard. The thermophoretic flux of nanoparticles is estimated to be very high from the hot flame onto the cold substrate. A highly hydrophobic coating was obtained by a mass loading in the order of 50-100 mg/m 2 of titanium dioxide on the paperboard.

Textile Research Journal, Aug 5, 2019

Healthcare associated infections (HAIs) are known as one of the major problems of the modern heal... more Healthcare associated infections (HAIs) are known as one of the major problems of the modern healthcare system, which result in additional cost and mortality. It has also been shown that pathogenic bacteria are mostly transferred via surfaces in healthcare settings. Therefore, antibacterial surfaces, which include fabrics and textiles, can be used in a healthcare environment to reduce the transfer of pathogenic bacteria, hence reducing HAIs. Silver nanoparticles have been shown to have broad spectrum antibacterial properties, and therefore they have been incorporated into fabrics to provide antibacterial functionality. Liquid flame spray (LFS) nanoparticle synthesis allows nanoparticles to be produced and deposited on surfaces at speeds up to and beyond 300 m/min. Herein, LFS is used to deposit silver nanoparticles onto two fabrics that are commonly used in the hospital environment with the aim of producing antibacterial fabrics. A thin plasma coating on top of the fabrics after silver deposition is used to improve nanoparticle adhesion. Fabrics coated with silver nanoparticles demonstrated antibacterial properties against Escherichia coli. Nanoparticle imaging and surface chemical characterization are performed using scanning electron microscopy and X-ray photoelectron spectroscopy. The highlights of this research are as follows: high-speed synthesis and deposition of silver nanoparticles on fabrics; plasma coating onto fabrics with silver nanoparticles; antibacterial fabrics for potential use in healthcare environments.

International Conference on Nanotechnology, 2010

• Liquid flame spray technology enables low-cost, large-scale nanoparticle deposition in roll-to-... more • Liquid flame spray technology enables low-cost, large-scale nanoparticle deposition in roll-to-roll processes for controlling wettability and creating functional surfaces • SiO2 nanocoating has higher abrasion resistance than TiO2 coating, possibly due to better interparticle sintering • Wettability properties of the LFS nanoparticle coated paperboard are partially maintained after abrasion with a paper surface or compression through calendering • The changes in wettability are due to smoothening of the nanoparticle surface Changes in wettability properties during transport and in converting operations can be expected to be small • Challenges: - Nanoparticle release to air and safety aspects are unknown and difficult to quantify • Potential applications: - Printability control - Improved barrier and heat-sealing properties for extrusion coated board - Adhesion promotion in converting - Liquid absorption control in papermaking and converting operations - Functional surfaces, e.g., self-cleaning surfaces - Printed electronics applications - Microfluidics.

Materials research express, Dec 5, 2018

Fabrication of superhydrophobic surfaces in large scale has been in high interest for several yea... more Fabrication of superhydrophobic surfaces in large scale has been in high interest for several years, also titanium oxide nanostructures having been applied for the purpose. Optimizing the amount and structure of the TiO2 material in the coating will play a key role when considering upscaling. Here, we take a look at fabricating the superhydrophobic surface in a one-step rollto-roll pilot scale process by depositing TiO2 nanoparticles from a Liquid Flame Spray onto a moving paperboard substrate. In order to find the minimum amount of nanomaterial still sufficient for creating superhydrophobicity, we varied nanoparticle production rate, flame distance from the substrate and line speed. Since the deposited amount of material sideways from the flame path was seen to decrease gradually, spatial analysis enabled us to consistently determine the minimum amount of TiO2 nanoparticles on the substrate needed to achieve superhydrophobicity. Amount as low as 20-30 mg/m 2 of TiO2 nanoparticles was observed to be sufficient. The scanning electron microscopy revealed that at this amount, the surface was covered with nanoparticles only partially, but still sufficiently to create a hierarchical structure to affect wetting significantly. Based on XPS analysis, it became apparent that TiO2 gathers hydrocarbons on the surface to develop the surface chemistry towards hydrophobic, but below the critical amount of TiO2 nanoparticles, the chemistry could not enable superhydrophobicity anymore. While varying the deposited amount of TiO2, besides the local spatial variance of the coating amount, also the overall yield was studied. Within the text matrix, a yield up to 44 % was achieved. In conclusion, superhydrophobicity was achieved at all tested line speeds (50 to 300 m/min), even if the amount of TiO2 varied significantly (20 to 230 mg/m 2).

Tampere University of Technology, Department of Physics, P.O. Box 692, FI-33101 Tampere, Finla... more 1) Tampere University of Technology, Department of Physics, P.O. Box 692, FI-33101 Tampere, Finland 2) University of Eastern Finland, Department of Applied Physics, P.O. Box 1627, FI-70211 Kuopio, Finland 3) University of Eastern Finland, Department of Environmental Science, P.O. Box 1627, FI-70211 Kuopio, Finland 4) VTT Technical Research Centre of Finland, Fine particles, P.O. Box 1000, FI-02044 VTT, Espoo, Finland 5) Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland 6) Aerodyne Research, 45 Manning Road, Billerica, MA 08121-3976, USA

Journal of Coatings Technology and Research, 2018

An atmospheric pressure aerosol-based wet thin film coating technique called the nFOG is characte... more An atmospheric pressure aerosol-based wet thin film coating technique called the nFOG is characterized and applied in polymer film coatings. In the nFOG, a fog of droplets is formed by two air-assist atomizers oriented toward each other inside a deposition chamber. The droplets settle gravitationally and deposit on a substrate, forming a wet film. In this study, the continuous deposition mode of the nFOG is explored. We determined the size distribution of water droplets inside the chamber in a wide side range of 0.1-100 lm and on the substrate using aerosol measurement instruments and optical microscopy, respectively. The droplet size distribution was found to be bimodal with droplets of approximately 30-50 lm contributing the most to the mass of the formed wet film. The complementary measurement methods allow us to estimate the role of different droplet deposition mechanisms. The obtained results suggest that the deposition velocity of the droplets is lower than the calculated terminal settling velocity, likely due to the flow fields inside the chamber. Furthermore, the mass flux of the droplets onto the substrate is determined to be in the order of 1 g/m 3 s, corresponding to a wet film growth rate of 1 lm/s. Finally, the nFOG technique is demonstrated by preparing polymer films with thicknesses in the range of approximately 0.1-20 lm.

Advanced Materials Interfaces, 2018

Nordic Pulp & Paper Research Journal, 2016

This paper has been peer-reviewed but does not include the final publisher proof-corrections or j... more This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.

Applied Physics Letters, 2017

Slippery, liquid-infused porous surfaces offer a promising route for producing omniphobic and ant... more Slippery, liquid-infused porous surfaces offer a promising route for producing omniphobic and anti-icing surfaces. Typically, these surfaces are made as a coating with expensive and time consuming assembly methods or with fluorinated films and oils. We report on a route for producing liquid-infused surfaces, which utilizes a liquid precursor fed oxygen-hydrogen flame to produce titania nanoparticles deposited directly on a low-density polyethylene film. This porous nanocoating, with thickness of several hundreds of nanometers, is then filled with silicone oil. The produced surfaces are shown to exhibit excellent anti-icing properties, with an ice adhesion strength of ∼12 kPa, which is an order of magnitude improvement when compared to the plain polyethylene film. The surface was also capable of maintaining this property even after cyclic icing testing.

We have developed a new method to deposit functional coatings on large areas on packaging materia... more We have developed a new method to deposit functional coatings on large areas on packaging materials such as paper, paperboard and polymer laminates. The coatings are deposited in a pilot scale on roll-to-roll materials with line speeds from 30 m/min up to 150 m/min. Functional properties such as hydrophilicity have been introduced using flame, plasma or corona treatment on the materials. Here, we have solved the problem by depositing nanocoating on the material. Nanocoating will have a chemical effect, which is permanent and does not decrease in the course of time as it does with conventional treatments. For example hydrophilic nature of the coating on paper material is advantageous in printing applications as water-based inks wet the surface more evenly. In this study, we demonstrate that it is possible to portably control the water contact angle on paperboard materials from 10 up to 160 with Liquid Flame Spray (LFS) nanocoatings of several ceramic particles e.g. TiO2 and SiO2. The...

Large area printed conductive surfaces are expected to have an impact on printed functionality ra... more Large area printed conductive surfaces are expected to have an impact on printed functionality ranging from electronics to photonics such as printed solar cells. We report here a study on formation of such conductive surfaces by flexographic printing using a PEDOT:PSS conductive ink on various coated papers. Printability of multilayer coated paper and TiO2 nanoparticle coated paperboard generated by the liquid flame spray process are compared to plastic film typically used in printed functionality applications. The wettability of TiO 2 nanoparticle coating can be altered between superhydrophobic and superhydrophilic states by ultraviolet light. It is observed that superhydrophobicity of paperboard induced by TiO2 nanoparticles results in poorer ink setting with the water-based PEDOT:PSS yielding lower conductivities. Therefore, we observe conductivity only after several successive prints. A solvent-based silver ink was used for comparison. It is believed that renewable natural fibre...