Martti Toivakka

Åbo Akademi University · Faculty of Science and Engineering

Barrier coatings derived from synthetic polymers have been widely used as protective layers in packaging applications. In this work, water dispersions of suberin, a natural polyester of birch bark with inherent hydrophobicity properties, were revealed as a sustainable and green alternative barrier layer in fiber-based packaging. Suberin fractions w...

This study aimed to understand the effect of various rheological additives on the extensional viscosity of barrier coating dispersions, as well as to understand the role extensional viscosity plays in stabilizing a liquid curtain. The apparent extensional viscosity was measured using two devices that create accelerating flows: a capillary viscomete...

The mechanical properties of paper coating layers are important in converting operations such as calendering, printing, and folding. While several experimental and theoretical studies have advanced our knowledge of these systems, a particle level understanding of issues like crack-at-the-fold are lacking. A discrete element method (DEM) model is us...

In this work a multilayer barrier paper-board was produced in a roll-to-roll process by slot-die coating of nanocellulose (microfibrillated cellulose or carboxymethylated cellulose nanofibrils) followed by extrusion coating of biodegradable thermoplastics (polylactic acid, polybutylene adipate tere-phthalate and polybutylene succinate). Hyperplaty...

Fabricating bio‐latex colloids with core–shell nanostructure is an effective method for obtaining films with enhanced mechanical characteristics. Nano‐sized lignin is rising as a class of sustainable nanomaterials that can be incorporated into latex colloids. Fundamental knowledge of the correlation between surface chemistry of lignin nanoparticles...

In this work a multilayer barrier paperboard was produced in a roll-to-roll process by slot-die coating of nanocellulose (microfibrillated cellulose (MFC) or carboxymethylated cellulose nanofibrils (CNF)) followedby extrusion coating of biodegradable thermoplastics (polylactic acid (PLA), polybutylene adipate terephthalate (PBAT) and polybutylene s...

The leakage issue and inferior heat conduction of organic phase change materials (PCMs) limit their actual applications. In the present study, cellulose nanofibril (CNF)-based foams were prepared as the porous scaffolds for polyethylene glycol (PEG) and paraffin wax (Pw) to prevent their leakage, and multiwalled carbon nanotubes (CNTs) were incorpo...

Sensitivity response is a critical parameter that decides the domain of dielectric materials to be implemented as piezocapacitive sensors for low- or high-pressure sensing applications. Here, we have clarified the sensitivity response behavior of three low-cost dielectric materials, two biodegradable paperboards and one acoustic polymeric foam. The...

We investigated the effect of polymers on the cracking of particulate coating layers. Carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) were used as contrasting polymer additives due to their different surface charges and film characteristics. Drying stress that generates cracking in particulate layers increased with the addition of both po...

To date, the energy-intensive production and high-water content severely limits nanocellulose applications on a large scale off-site. In this study, adding water-soluble polysaccharides (PS) to achieve an integrated process of water-redispersible nanocellulose production was well established. The addition of PS, in particular carboxymethylated-gala...

This is the first time to report a facile strategy to fabricate galactoglucomannan-based latex with highly transparent, hydrophobic and flexible characteristics by combining etherification with subsequent emulsion polymerization. The allylated galactoglucomannans (A-GGM) and galactoglucomannan-based latexes (GGM-L) were prepared and their chemical...

There is an ever-increasing interest towards utilizing nanocellulose as barrier coatings and films, with many companies moving towards pilot scale production of nanocellulose to be used primarily for barrier coatings. However, high suspension viscosity and yield stress, poor adhesion to substrates, poor moisture sensitivity, and additional drying i...

Salt hydrate phase change materials (PCMs) have been intensively used for thermal energy storage (TES) due to their sharp melting points, high energy storage density, small volume change and low cost. However, the problems of phase separation, supercooling and relatively low thermal conductivity of salt hydrate PCMs need to be addressed for high-ef...

Bio-based nanocellulosic materials are non-toxic, renewable, exhibit excellent barrier properties, and are suitable candidates for sustainable food packaging applications. Sizing and designing coating parameters for slot-coating process using nanocellulose suspensions is challenging due to complex shear-thinning rheology and the presence of a water...

The leakage and low thermal conductivity of paraffin phase change material (PCM) must be addressed to achieve a more efficient energy storage process. In this study, cellulose nanofibril (CNF) foams were prepared as the porous support of paraffin to prevent its leakage, and multiwalled carbon nanotubes (CNTs) were incorporated in the foams to impro...

Mineral coatings manipulate surface properties such as roughness, porosity, wettability and surface energy. Properties that are known to determine cell behaviour. Therefore, mineral coatings can potentially be used to manipulate cell fate. This paper studies mineral-cell interactions through coatings in a stacked cell culture platform. Minerals wer...

Thermal energy storage (TES) systems using phase change materials (PCMs) are of increasing interest for more efficient energy utilization. Herein, sodium sulfate decahydrate (Na2SO4·10H2O; SSD)/nanofibrillated cellulose (NFC)/graphite PCM composites were prepared by a simple blending method. NFC and graphite were used to improve the performance of...

Two series of well-defined lignin fractions derived from birch and spruce alkaline lignin (AL) by sequential solvent fractionation (i-PrOH-EtOH-MeOH) were engaged in a structure–property-application relationship study. The bacterial-derived alkaliphilic laccase (MetZyme) extensively catalyzed the oxidation and polymerization of AL fractions in an a...

Thermal energy storage (TES) has attracted intense attention because of its positive contribution to sustainable energy utilization. To improve the TES performance of sodium acetate trihydrate (SAT), the combined use of cellulose nanofibril (CNF) and graphene nanoplatelet (GNP) was investigated to tackle the phase separation problem and to improve...

High-consistency processing of fibrillated cellulose materials is attractive for commercial applications due to potential for lowered production costs, energy savings and easier logistics. The current work investigated structure–property relationships of fibrillated cellulose suspensions produced at 20% consistency using VTT HefCel (High-consistenc...

Salt hydrate phase change materials (PCMs) possess the challenge of supercooling, which must be addressed to allow more efficient energy storage and utilisation. In this work, cellulose nanofibril (CNF), a versatile biopolymer was used to support and disperse silver nanoparticles (AgNPs), and the synthesised CNF/AgNPs composite was used to improve...

Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontoxic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effecti...

We investigate the terahertz complex conductivity spectra of cellulose nanocrystal (CNC) based composite films fabricated with different blending ratios of the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and without/with glycerol additive. A partially localized nature of carriers in the composite is clear...

Poly(3,4-ethylenedioxythiophene) doped with the polymer anion poly(styrenesulfonate), PEDOT:PSS, is a common electrochromic material used in the preparation of electrochromic devices (ECDs). In this paper, the PEDOT:PSS doped with a solvent was used both as the electrode and the electrochromic functional layer for fabrication of ECDs on absorptive...

Fibrillated cellulose can be used as a gelation agent to thicken and improve phase stability of sodium sulfate decahydrate (SSD, Na2SO4·10H2O), a promising salt hydrate for storing thermal energy. It is expected that dissolved SSD influences the thickening action by changing the colloid interactions between the cellulose fibrils. The fibrillation d...

The current work aims at understanding factors that influence the processability of nanographite-nanocellulose suspensions onto flexible substrates for production of conductive electrodes. A custom-built slot-die was used in a continuous roll-to-roll process to coat the nanomaterial suspension onto substrates with varying surface smoothness, thickn...

Due to the high electric conductivity and large surface area of nanographites, such as graphene and graphite nanoplatlets, these materials have gained a large interest for use in energy storage devices. However, due to the thin flake geometry, the viscosity of aqueous suspensions containing these materials is high even at low solids contents. This...

Biodegradable and renewable materials, such as cellulose nanomaterials, have been studied as a replacement material for traditional plastics in the biomedical field. Furthermore, in chronic wound care modern wound dressing, hydrogels and active synthetic extracellular matrices promoting tissue regeneration, are developed to guide cell growth and di...

A paper-based platform was developed and tested for studies on basic cell culture, material biocompatibility, and activity of pharmaceuticals in order to provide a reliable, robust and low-cost cell study platform. It is based upon a paper or paperboard support, with a nanostructured latex coating to provide an enhanced cell growth and sufficient b...

Stencil printing is a commonly used printing method, but it has not previously been used for production of pharmaceuticals. The aim of this study was to explore whether stencil printing of drug containing polymer inks could be used to manufacture flexible dosage forms with acceptable mass and content uniformity. Formulation development was supporte...

In the original version of this article, one of the concentrations of CNF suspensions has been reported to be 0.01% under the results and discussion of rheology measurements. It should have been 0.1% instead.

Continuous cyclization of citronellal over zeolite-based extrudates was performed in a trickle-bed reactor at 35 – 70 °C and 10 bar of argon. Catalytic results were correlated with the physico-chemical properties of the shaped catalyst prepared by extrusion of Beta or Y zeolites with binders. Rheological tests were used to elucidate the flow proper...

The mechanical properties of pigmented coating layers are important in a variety of applications. However, the large number of parameters that influence these properties as well as the numerous types of deformations challenge the prediction of the performance of these systems. A discrete element method (DEM) is proposed to predict the mechanical pr...

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...

A straightforward and reliable method was successfully developed for stainless steel microreactor coating. The importance ofthiscoatingmethodliesinusinganalreadypre-preparedAu/Al2O3 catalystwithoutincorporation of any binders, addressing the importance of the interplay between the catalyst particle size and slurry viscosity in optimization of the u...

Rheology of Microfibrillated Cellulose (MFC) suspensions is useful for designing equipment to transport, mix, or process them. Pressure-driven flow behavior is particularly important for MFC suspensions if they are to be pumped, extruded or coated. Herein, we report use of slot and pipe geometries for determination of MFC suspension rheology and co...

Traditional cell culture relies mostly on flat plastic surfaces, such as Petri dishes and multiwell plates. These commercial surfaces provide limited flexibility for experimental design. In contrast, cell biology increasingly demands surface customisation, functionalisation, and cell monitoring in order to obtain data that is relevant in vivo. The...

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 (Saureus) and gram negative Escherichia c...

Recent years have seen an increased interest towards utilizing bio-based and biodegradable materials for barrier packaging applications. Most of the above said materials usually have certain shortcomings that discourage their adoption as a preferred material of choice. Nanocellulose falls into such category. It has excellent barrier against grease,...

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...

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...

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...

There is an increased interest in the use of cellulose nanocrystal (CNC) films and coatings for a range of functional applications in the fields of material science, biomedical engineering, and pharmaceutical sciences. Most of these applications have been demonstrated on films and coatings produced using laboratory-scale batch processes, such as so...

In this study hierarchically-structured latex polymer coatings and self-supporting films were characterised and their suitability for cell growth studies was tested with Human Dermal Fibroblasts (HDF). Latex can be coated or printed on rigid or flexible substrates thus enabling high-throughput fabrication. Here, coverslip glass substrates were coat...

Nanocellulose is a material of interest for biomedical applications due to its morphological similarity with tissues’ own collagen. New cell culture substrates that mimic the human body tissue stiffness and extracellular matrix can be used to study cell behaviour in a way that is not possible for traditional plastic substrates. Five wood-based micr...

Minerals are versatile tools utilised to modify and control the physical-chemical and functional properties of substrates. Those properties include ones directing cell fate; thus, minerals can potentially provide a direct and inexpensive method to manipulate cell behaviour. This paper shows how different minerals influence human dermal fibroblast b...

Amino acid functionalised bacterial cellulose is a non-toxic biocompatible material, which can be further modified with active groups and nanoparticles for various biomedical applications. Many studies have focused mainly on the chemical and biomedical characterisation of modified bacterial cellulose; however, the mechanical performance of these ma...

Constantly growing interest in nanocellulose usage and applications is pushing the scientific community to search for suitable production and processing techniques. One example is use of nanocellulose as a barrier material in packaging applications, which requires processing of nanocellulose into films and coatings. It is challenging to coat nanoce...

Bacterial infections, especially by antimicrobial resistant (AMR) bacteria, are an increasing problem worldwide. AMR is especially a problem with health care-associated infections due to bacteria in hospital environments being easily transferred from patient to patient and from patient to environment, and thus, solutions to prevent bacterial transm...

Silver nanoparticles are widely used as antibacterial agents in consumer products. There have been concerns about the environmental exposure and their toxic effect to organisms such as fish. Studies have quantified the release of silver from various products including textiles and plastics that use silver as an antibacterial agent, yet there is no...

Paper products with active and functional coatings have attracted interest in recent years to counter the stagnating demand for traditional graphic paper grades. Conductive coatings have potential uses in various energy generation and storage applications, e.g. in batteries, supercapacitors, and photovoltaics. The current work aims to demonstrate l...

Cellulose nanofibril (CNF) suspensions are not easily coatable because of their excessively high viscosity and yield stress, even at low solids concentrations. In addition, CNF suspensions vary widely in their properties depending on the production process used, which can affect their processability. This work reports roll-to-roll coating of three...

This chapter reviews the recent advances in achieving green electronics using cellulosic paper and fibers as a substrate for electronics. It focuses on the paper substrate, individual component development, and the use of paper for sensing purposes in both analytical and point-of-care applications. While using paper as a substrate is difficult, sin...

The reduction of binder concentration in coatings, within the constraints of acceptable final paper quality, is a constant focus for cost effective production of paper and board coatings. As binder levels are reduced, issues of strength and printability become more and more critical, due to the increasing probability of creating a heterogeneous bin...

Cellulose nanofibrils (CNF) are, due in large part to excellent gas barrier properties, a potential environmentally friendly alternative to inorganic and petrochemical coatings of e.g. paperboard in packaging applications. In the current paper successful roll-to-roll coating of three qualities of CNF is demonstrated on a recycled quality, porous pa...

Nanoparticles are used in several applications due to the unique properties they possess compared to bulk materials. Production techniques have continuously evolved over the years. Recently, there has been emphasis on environmentally friendly manufacturing processes. Substrate properties often limit the possible production techniques and, for examp...

Cellulose nano- and microfibrils (CNF/CMF) grades vary significantly based on the raw materials and process treatments used. In this study four different CNF/CMF grades were combined with kaolin clay pigment particles to form nanoporous composites. The attained composite properties like porosity, surface smoothness, mechanical properties and densit...

Paper-based microfluidics is an emerging field focused on creating inexpensive devices, with simple fabrication methods for applications in various fields including healthcare, environmental monitoring and veterinary medicine. Understanding the flow of liquid is important in achieving consistent operation of the devices. This paper proposes capilla...

Paper-based microfluidics is an emerging field focused on creating inexpensive devices, with simple fabrication methods for applications in various fields including healthcare, environmental monitoring and veterinary medicine. Understanding the flow of liquid is important in achieving consistent operation of the devices. This paper proposes capilla...

Interest in nanocellulose-based coatings for packaging applications has been growing due to their excellent oil and gas barrier properties combined with their sustainable, recyclable, biodegradable, and non-toxic nature. Coating of nanocellulose materials such as microfibrillated cellulose (MFC) on paper/paperboard is challenging compared to tradit...

We demonstrate roll-to-roll fabrication of ultraviolet A light-activated colorimetric oxygen indicators on paper and plastic substrates. Such large-scale, cost-effective and non-toxic oxygen indicator and production method can find applications as a very low-cost leakage indicator for modified atmosphere packages by printing the material directly o...

Cellulose nanofibers (CNFs) are an exciting new renewable material produced from wood fibers. Even at low solids content, CNF-water suspensions have a complex rheology that includes extreme shear-thinning as well as viscoelastic properties and a yield stress similar to other suspensions of nanoscale particles. When characterizing the rheology of CN...

Paper-based microfluidic devices have received considerable interest due to their benefits with regards to low manufacturing costs, simplicity and the wide scope of applications. However, limitations including sample retention in paper matrix and evaporation as well as low liquid flow rates have often been overlooked. This paper presents a paper-ba...

A new design for permanent, low-cost, and planar fluidic channels on TiO2 nanoparticle coated paperboard is demonstrated. Initially superhydrophobic TiO2 nanoparticle coatings can be converted to hydrophilic by ultraviolet (UVA) light, and fluidic channels can be generated. A simple water treatment after the UVA illumination converts the channels p...