Lasse Murtomaki
Aalto University, Department of Chemistry, Faculty Member
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An experimental verification of the previously introduced model for transdermal transport (Kontturi and Murtomäki, J. Control. Release, 41 (1996) 177) is presented. The model comprises two penetration routes: an aqueous and a lipoidal... more
An experimental verification of the previously introduced model for transdermal transport (Kontturi and Murtomäki, J. Control. Release, 41 (1996) 177) is presented. The model comprises two penetration routes: an aqueous and a lipoidal pathway. Lipophilicity of the drug determines which route the drug uses. Constant potential iontophoresis can be used to evaluate the relative proportions of the two competing pathways. beta-blockers sotalol, timolol and propranolol, whose water-octanol partition coefficients span three orders of magnitude, are used as model compounds. Experiments reinforce the predictions of the model in that iontophoresis enhances the flux of the most hydrophilic drug, sotalol, the most whereas the flux of the least hydrophilic drug, propranolol, is enhanced the least. The effect of electroosmosis has now been included in the model.
Research Interests: Chemistry, Biomedical Engineering, Kinetics, Medicine, Drug Use, and 12 moreHumans, Controlled release, Mathematical Computing, Partition Coefficient, Iontophoresis, Lipophilicity, Reproducibility of Results, Propranolol, Transdermal, Skin Absorption, Pharmacology and pharmaceutical sciences, and timolol
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Mg and Mg alloys offer a great potential for use as a biomedical material for temporary implant applications: its lack of toxicity, ability to easily dissolve in aqueous environments, and its bone-like bulk properties. One of the key... more
Mg and Mg alloys offer a great potential for use as a biomedical material for temporary implant applications: its lack of toxicity, ability to easily dissolve in aqueous environments, and its bone-like bulk properties. One of the key drawbacks however, that prevents the more widespread use of magnesium-based materials is their fast and often uncontrollable corrosion within the human body that impedes its utilisation in a wide range of orthopaedic components1,2. The possibility to control this dissolution is vital if Mg alloys are to be considered as a practical, temporary biomedical implant materials. In this study we detail how this aim can be attained by the use of biocompatible polymeric membrane materials. For example, by using a polyelectrolyte like poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) to modify cellulose acetate (CA) membranes it is possible to achieve Mg dissolution control. Commercially pure magnesium surfaces were spin-coated with differing concentrations of ...
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Research Interests: Materials Science, Copper, Membrane, Energy Storage, Vanadium, and 4 moreFlow Battery, Electrode, Redox, and Electrolyte
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Ionic diffusion coefficients in the membrane are needed for the modelling of ion transport in ion‐exchange membranes (IEMs) with the Nernst‐Planck equation. We have determined the ionic diffusion coefficients of Na+, OH−, H+, Cl−, SO42−,... more
Ionic diffusion coefficients in the membrane are needed for the modelling of ion transport in ion‐exchange membranes (IEMs) with the Nernst‐Planck equation. We have determined the ionic diffusion coefficients of Na+, OH−, H+, Cl−, SO42−, NaSO4−, and HSO4− from the diffusion experiments of dilute NaCl, NaOH, HCl, Na2SO4, and H2SO4 solutions through IEMs and the membrane conductivity measured in these solutions, using electrochemical impedance spectroscopy. The order of diffusion fluxes across the anion‐exchange membrane is found to be as H2SO4>HCl>NaCl>Na2SO4>NaOH, whereas for the cation‐exchange membrane it was NaOH>NaCl>Na2SO4≥H2SO4. Special attention is given to sulfates because of the partial dissociation of bisulfate and NaSO4−, which makes the use of the Nernst‐Hartley equation, that is, splitting the electrolyte diffusion coefficient into its ionic contributions, impossible. The expression of the diffusion coefficient of sulfates taking into account the dissociation equilibrium has been derived and the corresponding Fick equation has been integrated. In addition, for sulfates, finite element simulations with COMSOL Multiphysics, applying a homogeneous membrane model, were done to give estimates of their ionic diffusion coefficients. This work offers a convenient approach to finding diffusion coefficients of various ions inside IEMs.
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Redox flow batteries are an emergent technology in the field of energy storage for power grids with high renewable generator penetration. The copper redox flow battery (CuRFB) could play a significant role in the future of electrochemical... more
Redox flow batteries are an emergent technology in the field of energy storage for power grids with high renewable generator penetration. The copper redox flow battery (CuRFB) could play a significant role in the future of electrochemical energy storage systems due to the numerous advantages of its all-copper chemistry. Furthermore, like the more mature vanadium RFB technology, CuRFBs have the ability to independently scale power and capacity while displaying very fast response times that make the technology attractive for a variety of grid-supporting applications. As with most batteries, the efficient operation of a CuRFB is dependent on high-quality control of both the charging and discharging process. In RFBs, this is typically complicated by highly nonlinear behaviour, particularly at either extreme of the state of charge. Therefore, the focus of this paper is the development and validation of a first-principle, control-appropriate model of the CuRFBs electrochemistry that inclu...
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Aqueous copper redox flow batteries (CuRFB) based systems offer an alternative, more sustainable, redox flow battery to those based on vanadium for stationary renewable energy storage. Copper is an abundant material (~20 million tonnes/... more
Aqueous copper redox flow batteries (CuRFB) based systems offer an alternative, more sustainable, redox flow battery to those based on vanadium for stationary renewable energy storage. Copper is an abundant material (~20 million tonnes/ year), that can be easily recycled and is significantly lower cost (6.5 € kg -1), by comparison with vanadium technology (20 € kg-1)[i]. CuRFBs can also be operated without perfluorinated membranes required in the vanadium redox flow batteries (VRFB). The CuRFB system takes advantage of the three stable oxidation states of copper Cu(0)-Cu(I)–Cu(II) in which the cuprous species are oxidised to cupric species in the positive half-cell and electrochemically deposited as copper on the negative electrode. The electrolyte system investigated in this work is based on chloride salts which are soluble up to 2.5 M[ii] ,[iii] . This concentration level enables high current densities to be achieved assisting with high power delivery. The present study was focuss...
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Abstract Thermodiffusion, or the Soret phenomenon, is well understood in simple systems, but in multicomponent and polyvalent electrolyte systems the process becomes more complicated due to the coupling of fluxes. We experimentally... more
Abstract Thermodiffusion, or the Soret phenomenon, is well understood in simple systems, but in multicomponent and polyvalent electrolyte systems the process becomes more complicated due to the coupling of fluxes. We experimentally investigate the time evolution of a concentration gradient generated by thermodiffusion of a polyelectrolyte (poly(sodium 4-styrene sulfonate), NaPSS) in a 1:1 supporting electrolyte. We also derive and solve the transport equations that are used to extract the Soret coefficient from the experimental observations. It is shown that NaPSS thermodiffusion in NaCl is strongly dependent on concentration, with almost 100% thermal separation in concentrations below 15 nmol L−1. Moreover, the results suggest that the supporting electrolyte can greatly influence the thermodiffusion of the polyelectrolyte, in some cases possibly even reversing the direction of the flux from the usual case of enrichment at the cold side.
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Abstract 1D axial dispersion and 3D CFD models for the extraction of levulinic acid from dilute aqueous solution by applying 2-methyltetrahydrofuran as a solvent are presented. The models are validated by comparison with the measured... more
Abstract 1D axial dispersion and 3D CFD models for the extraction of levulinic acid from dilute aqueous solution by applying 2-methyltetrahydrofuran as a solvent are presented. The models are validated by comparison with the measured levulinic acid concentration profile data obtained in a bench-scale Kuhni column. The 1D model contains NRTL parameters for the system levulinic acid-water-2MTHF. Correlations for drop size and hold-up for Kuhni columns were taken from literature. The values for overall mass transfer coefficient ranged from 1.4E-5 to 2.2E-5 ms−1, and increased as a function of the rotor speed. The fitting of the column performance resulted in a very good prediction of the solute concentration profiles in the extraction column, and the average absolute value of relative error for the 1D model was 23%. CFD model visualized the column performance at the column height of 150.5–160 cm giving valuable information on back mixing, phase velocities, dispersed phase volume fraction, and mass transfer. Dispersed phase volume fraction and mass transfer contours revealed, that the mass transfer rate (app. 0.25 g L−1s−1) is at its highest just below the rotor, and that there are blind spots in the compartments close to the extractor and just above each down comer. Values for the dispersed phase volume fraction are highest in the same area where the mass transfer reaches the highest values. The highest slip velocity values (app. 0.03 m−1) are located in the tip of each compartment partition plates. General correlations, such as hold-up and drop size correlations, can successfully be applied in levulinic acid-water-2MTHF system reported in this work. The 1D axial dispersion model proved to be valuable tool for scale-up purposes, and CFD model, despite the long time needed for each simulation, gave useful information for the design purposes.
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In light-activated liposomal drug delivery systems (DDSs), the light sensitivity can be obtained by a photothermal agent that converts light energy into heat. Excess heat increases the drug permeability of the lipid bilayer, and drug is... more
In light-activated liposomal drug delivery systems (DDSs), the light sensitivity can be obtained by a photothermal agent that converts light energy into heat. Excess heat increases the drug permeability of the lipid bilayer, and drug is released as a result. In this work, two near-IR responsive photothermal agents in a model drug delivery system are studied: either gold nanorods (GNRs) encapsulated inside the liposomes or indocyanine green (ICG) embedded into the lipid bilayer. The liposome system is exposed to light, and the heating effect is studied with fluorescent thermometers: laurdan and CdSe quantum dots (QDs). Both photothermal agents are shown to convert light into heat in an extent to cause a phase transition in the surrounding lipid bilayer. This phase transition is also proven with laurdan generalized polarization (GP). In addition to the heating results, we show that the model drug (calcein) is released from the liposomal cavity with both photothermal agents when the light power is sufficient to cause a phase transition in the lipid bilayer.
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ABSTRACT