Microfluidics & Nanofluidics

Tavari, T., Meamardoost, S., Sepehry, N., Sepehry, N., Akbarzadeh, P., Nazari, M., Hashemi, N.N. & Nazari, M. (2022). Effects of 3D electrodes arrangement in a novel AC electroosmotic micropump: Numerical modeling and experimental validation. Electrophoresis. 2022; 1– 12.
https://doi.org/10.1002/elps.20220021

Keywords: electrode optimization, electroosmotic micropump, microchip, microfabrication, microfluidic

Membranes for Specific Adsorption: Immobilizing Molecularly Imprinted Polymer Microspheres using Electrospun Nanofibers
Büttiker, Roman; Ebert, Jürgen; Hinderling, Christian; Adlhart, Christian. CHIMIA International Journal for Chemistry, Volume 65, Number 3, March 2011, pp. 182-186(5).
Zurich University of Applied Sciences ZHAW, Institute of Chemistry and Biological Chemistry, Einsiedlerstrasse 31, 8820 Wädenswil
Keywords: Electrospinning; Filtration; Molecularly imprinted polymer; Precipitation polymerization; Raman microscopy ¹³C.

Abstract: Molecularly imprinted polymer microspheres were immobilized within a polymer nanofiber membrane by electrospinning. Such membranes simplify the handling of functional microspheres and provide specific recognition capabilities for solid-phase extraction and filtration applications. In this study, microspheres were prepared by precipitation polymerization of methacrylic acid and divinylbenzene as a cross-linker with the target molecule (−)-cinchonidine and then, they were electrospun into a non-woven polyacrylonitrile nanofiber membrane. The composite membrane showed specific affinity for (−)-cinchonidine which was attributed to the functional microspheres as confirmed by Raman microscopy.

Silica is preferred over various single and mixed oxides as support for CO₂-assisted cobalt-catalyzed oxidative dehydrogenation of ethane
Rajesh Koirala, Robert Buechel, Sotiris E. Pratsinis, Alfons Baiker. Applied Catalysis A: General. Volume 527, 25 October 2016, Pages 96–108.
Department of Mechanical and Process Engineering & Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland.
Keywords: Oxidative dehydrogenation; Cobalt; Single and mixed oxide supports; Ethane; Carbon dioxide; Flame spray pyrolysis.

Abstract: Catalysts containing 4.5 wt% cobalt supported on single oxides of SiO₂, Al₂O₃, TiO₂ and ZrO₂ and on mixed ones of SiO₂-Al₂O₃, SiO₂-TiO₂, SiO₂-ZrO₂ and TiO₂-ZrO₂ were produced in a single step by flame spray pyrolysis and tested in the CO₂-assisted oxidative dehydrogenation of ethane in a continuous fixed-bed microreactor. Structural and chemical properties of the nonporous catalysts were characterized by nitrogen adsorption, XRD, HR-TEM, EDXS, NH₃-TPD, H₂-TPR, TGA, DRIFTS, XPS and Raman and UV–vis spectroscopy. Depending on the supporting oxides the reducibility of the cobalt species varied in a broad range, indicating vastly different interaction of the cobalt species with the oxidic support.

Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition
Lidija Posavec, Jesper T. N. Knijnenburg, Florentine M. Hilty, Frank Krumeich, Sotiris E. Pratsinis, Michael B. Zimmermann. Journal of Nanoparticle Research (2016) 18: 310.
Human Nutrition Laboratory & Particle Technology Laboratory, ETH Zurich, Switzerland.
Keywords: Flame-assisted spray pyrolysis (FASP); Calcium carbonate; Calcium phosphate; Doping; Aging; Dissolution; Food.

Abstract: Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO₃) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO₃ made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO₃ and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO₃, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca₂P₂O₇ with increasing hydroxyapatite content at higher Ca:P.

Oxidative coupling of methane on flame-made Mn-Na2WO4/SiO2: Influence of catalyst composition and reaction conditions
Rajesh Koirala, Robert Büchel, Sotiris E. Pratsinis, Alfons Baiker. Applied Catalysis A: General, Volume 484, 22 August 2014, Pages 97–107 
Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland and Chemistry Department, Faculty of Science, King Abdulaziz University, Saudi Arabia.
Keywords: Oxidative methane coupling; Mn-Na₂WO₄/SiO₂; Flame spray pyrolysis; In situ XRD; Cristobalite SiO₂

Abstract: Mn-Na₂WO₄/SiO₂ catalysts of different composition were made in a single step by flame spray pyrolysis, a process that can be scaled up to a production rate in the range of kg/h. The multicomponent catalysts containing 0–5 wt% Mn and 0–6 wt% Na₂WO₄ were characterized by nitrogen adsorption, XRD, TEM, STEM, EDXS and TPR, and tested in the oxidative coupling of methane (OCM) in a continuous flow microreactor at different reaction conditions (temperature, CH₄/O₂ feed ratio, space time). As-prepared catalysts showed much higher specific surface area (SSA) and a more homogenous spatial distribution of the constituents than corresponding catalysts prepared by wet-impregnation. Upon exposure to reaction conditions at 810 °C the amorphous SiO₂component gradually transformed to crystalline cristobalite, as shown by in situ XRD.

Synthesis of Hetero-nanoclusters: The Case of Polymer–Magnetite Systems
Codari, Fabio, Davide Moscatelli, Marco Furlan, Marco Lattuada, Massimo Morbidelli, and Miroslav Soos. Langmuir, 2014, 30 (8), pp 2266–2273
Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland; Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di Milano, Italy.
Keywords: Nanoclusters (NCs); Nanoparticles (NPs); Drug delivery; Magnetite nanoparticles (MNPs); Hetero-NCs; Biomedical applications

Abstract: Nanoclusters (NCs) composed of nanoparticles (NPs) with different functionalities and having final size in the sub-micrometer range are of great interest for biomedical imaging, drug delivery, sensors, etc. Because some of the functionalities cannot be incorporated into a single NP, e.g., high drug loading combined with strong magnetic properties, here, we present a proof of the concept using an alternative way to combine these properties using different NPs. In particular, starting from polymer and magnetite nanoparticles (MNPs), we produce NCs made out of a statistical distribution of the two components through a process based on aggregation and breakup.

Synthesis of ZnO nanoparticles by flame spray pyrolysis and characterisation protocol
Wallace, R., A. P. Brown, R. Brydson, K. Wegner, and S. J. Milne. Journal of Materials Science 48, no. 18 (2013): 6393-6403.
Institute for Materials Research, SPEME, University of Leeds, UK; Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Switzerland.
Keywords: ZINC oxide - Research; NANOPARTICLES - Synthesis; TOXICITY testing - Research; PYROLYSIS; FLAME spraying; RESEARCH methodology evaluation; TOXICITY testing - In vitro

Abstract: There is uncertainty concerning the potential toxicity of zinc oxide (ZnO) nanoparticles, which may be attributed in part to a lack of understanding with regard to the physiochemical properties of the nanoparticles used in toxicological investigations. This paper reports the synthesis of a ZnO nanopowder by flame spray pyrolysis and demonstrates that the typically employed characterisation techniques such as specific surface area measurement and X-ray diffraction provide insufficient information on the sample, especially if it is intended for use in toxicity studies. Instead, a more elaborate characterisation protocol is proposed that includes particle morphology as well as detailed compositional analysis of the nanoparticle surface.

Nanoparticle synthesis in vesicle microreactors
Yang, Peng, and Rumiana Dimova. INTECH Open Access Publisher, 2011
Max Planck Institute of Colloids and Interfaces, Department of Theory and Bio-Systems, Potsdam, Germany.

Introduction: Numerous microorganisms such as E-coli and yeast are capable of synthesizing inorganic micro- or nano-structures including gold, silver, CdS, ZnS and calcium/silicon-based materials in their intra- or extra-cellular matrix (Sanchez et al, 2005; Mandal et al, 2006; Bhattacharya et al, 2005). Even though the widespread speculations propose that a few enzymes or peptides present in the organic matrix (mainly in cell walls and periplasmic space) act as reducing and nucleation sites (Mukherjee et al, 2001; Ahmad et al, 2002; Dameron et al, 1989; Umetsu et al, 2005; Kröger et al, 2006; Naik et al, 2002), the molecular basis for the biosynthesis of these materials is not well established.

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Nanoparticle synthesis in vesicle microreactors
Yang, Peng, and Rumiana Dimova. INTECH Open Access Publisher, 2011
ETH Zurich, Institute of Process Engineering, Department of Mechanical and Process Engineering, Particle Technology Laboratory, Zurich, Switzerland.
Keywords: Flame assisted spray pyrolysis, Flame spray pyrolysis, Gas phase synthesis, Low-cost production, Flame enthalpy density, Product homogeneity, Bimodal size distribution

Introduction: A new flame-assisted spray pyrolysis (FASP) reactor design is presented, which allows the use of inexpensive precursors and solvents (e.g., ethanol) for synthesis of nanoparticles (10–20 nm) with uniform characteristics. In this reactor design, a gas-assisted atomizer generates the precursor solution spray that is mixed and combusted with externally fed inexpensive fuel gases (acetylene or methane) at a defined height above the atomizing nozzle. The gaseous fuel feed can be varied to control the combustion enthalpy content of the flame and onset of particle formation. This way, the enthalpy density of the flame is decoupled from the precursor solution composition.

Characterization of an air‐spun poly (L‐lactic acid) nanofiber mesh
François, Sébastien, Christian Sarra‐Bournet, Antoine Jaffre, Nabil Chakfé, Bernard Durand, and Gaétan Laroche. Journal of Biomedical Materials Research Part B: Applied Biomaterials 493, no. 2 (2010): 531-543.
Université Laval, Canada; Centre de recherche du CHUQ, Hôpital Saint-Franóis d'Assise, Canada; Les Hôpitaux Universitaires de Strasbourg, France; GEPROVAS, France.
Keywords: PLLA; nanofibers; air spinning; atmospheric pressure plasma treatment; vascular prostheses

Abstract: It was previously showed that PLLA nanofiber mesh promoted good endothelial cell proliferation. A new technique was developed to produce nanofibers by air jet spinning inside the tubular shape of vascular prostheses and to characterize this nanofiber mesh. Polymer macromolecule stability was assessed by gel permeation chromatography. Thermal analyses were conducted with differential scanning calorimetry and dynamic mechanical analysis on PLLA nanofibers obtained with 4% and 7% solutions (w/v) in chloroform. Polyethylene terephthalate (PET) was also treated with atmospheric pressure dielectric barrier discharge under air or nitrogen atmosphere to optimize PLLA nanofiber adherence, assessed by peel tests.

Nanoparticle formation in giant vesicles: synthesis in biomimetic compartments
Yang, Peng, Reinhard Lipowsky, and Rumiana Dimova. small 5, no. 18 (2009): 2033-2037.
Max Planck Institute of Colloids and Interfaces, Department of Theory and Bio-Systems, Potsdam, Germany; Duke University, Department of Biomedical Engineering, Durham, USA.
Keywords: Biomimetic Synthesis; Membranes; Nanostructures; Quantum Dots; Vesicles

Abstract: Nanoparticles of CdS with radii of 4 or 50 nm are formed in a controlled fashion inside lipid giant vesicles. For this purpose, two protocols are developed: electrofusion of differently loaded vesicles and slow vesicle content exchange via lipid nanotubes (see image). The process of particle formation can be directly monitored with fluorescence microscopy. The approach can be used to form any kind of nanoparticle.