Publications by authors named "Daniel Florea"

6 Publications

  • Page 1 of 1

Compression and Reswelling of Microgel Particles after an Osmotic Shock.

Phys Rev Lett 2017 Sep 31;119(9):098001. Epub 2017 Aug 31.

Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600MB Eindhoven, The Netherlands.

We use dedicated microfluidic devices to expose soft hydrogel particles to a rapid change in the externally applied osmotic pressure and observe a surprising, nonmonotonic response: After an initial rapid compression, the particle slowly reswells to approximately its original size. We theoretically account for this behavior, enabling us to extract important material properties from a single microfluidic experiment, including the compressive modulus, the gel permeability, and the diffusivity of the osmolyte inside the gel. We expect our approach to be relevant to applications such as controlled release, chromatography, and responsive materials.
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http://dx.doi.org/10.1103/PhysRevLett.119.098001DOI Listing
September 2017

Surgical Treatment of a Rare "Reverse" Madelung Deformity in 11 Years Female Patient.

Chirurgia (Bucur) 2017 Jan-Feb;112(1):72-76

Madelung deformity is an abnormality of the distal part of the forearm due to a growth arrest in the distal radial physis creating an increase of the radial tilt angle associated with a dorsal subluxation of the distal ulna in most cases. It is a rare condition which represents only 1.7% of hand deformities being characterized by the presence of an abnormal structure, Vickers ligament, that tethers the distal radius to the lunate bone. Although it is believed to be a congenital disorder, the symptoms are absent till late childhood. We present a case of a 11 years old girl patient, who came to our clinic for deformity of both forearms, which consisted of an anteriorly curved radius, volar proeminence of the distal ulna, partial limitation of supination and pain in the last 6 months, with and insidious onsed and aggravated lately. The mother of the patient, at the age of 13, was diagnosed with the same deformity which was surgically treated at that time. Furthermore, the patient has an older sister with no deformity of the forearms. X-rays revealed an increased radial tilt and anterior luxation of the distal ulna. Considering the deformity and the presence of pain we decided to excise the Vickers ligament and make an opening and derotation wedge osteotomy of the distal radius.
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http://dx.doi.org/10.21614/chirurgia.112.1.72DOI Listing
June 2017

Convection associated with exclusion zone formation in colloidal suspensions.

Soft Matter 2016 Jan;12(4):1127-32

Department of Mechanical Engineering, Materials Technology, Eindhoven University of Technology, Eindhoven, The Netherlands. and Bernal Institute, University of Limerick, Limerick, Ireland.

The long-range repulsion of colloids from various interfaces has been observed in a wide range of studies from different research disciplines. This so-called exclusion zone (EZ) formation occurs near surfaces such as hydrogels, polymers, or biological tissues. It was recently shown that the underlying physical mechanism leading to this long-range repulsion is a combination of ion-exchange at the interface, diffusion of ions, and diffusiophoresis of colloids in the resulting ion concentration gradients. In this paper, we show that the same ion concentration gradients that lead to exclusion zone formation also imply that diffusioosmosis near the walls of the sample cell must occur. This should lead to convective flow patterns that are directly associated with exclusion zone formation. We use multi-particle tracking to study the dynamics of particles during exclusion zone formation in detail, confirming that indeed two pronounced vortex-like convection rolls occur near the cell walls. These dramatic flow patterns persist for more than 4 hours, with the typical velocity decreasing as a function of time. We find that the flow velocity depends strongly on the surface properties of the sample cell walls, consistent with diffusioosmosis being the main physical mechanism that governs these convective flows.
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http://dx.doi.org/10.1039/c5sm01502bDOI Listing
January 2016

Long-range repulsion of colloids driven by ion exchange and diffusiophoresis.

Proc Natl Acad Sci U S A 2014 May 18;111(18):6554-9. Epub 2014 Apr 18.

Department of Mechanical Engineering and Institute for Complex Molecular Systems , Eindhoven University of Technology, 5612 AZ, Eindhoven, The Netherlands.

Interactions between surfaces and particles in aqueous suspension are usually limited to distances smaller than 1 μm. However, in a range of studies from different disciplines, repulsion of particles has been observed over distances of up to hundreds of micrometers, in the absence of any additional external fields. Although a range of hypotheses have been suggested to account for such behavior, the physical mechanisms responsible for the phenomenon still remain unclear. To identify and isolate these mechanisms, we perform detailed experiments on a well-defined experimental system, using a setup that minimizes the effects of gravity and convection. Our experiments clearly indicate that the observed long-range repulsion is driven by a combination of ion exchange, ion diffusion, and diffusiophoresis. We develop a simple model that accounts for our data; this description is expected to be directly applicable to a wide range of systems exhibiting similar long-range forces.
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http://dx.doi.org/10.1073/pnas.1322857111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4020040PMC
May 2014

Towards the self-assembly of anisotropic colloids: monodisperse oblate ellipsoids.

J Colloid Interface Sci 2014 Feb 28;416:30-7. Epub 2013 Oct 28.

Eindhoven University of Technology, Materials Technology, Eindhoven, Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands. Electronic address:

We present a robust and straightforward method for producing colloidal particles of oblate ellipsoidal shape via thermo/mechanical stretching of elastomeric films with embedded spherical particles. Our method produces uniformly sized and shaped colloidal particles. The method can be used for producing biaxially stretched particles of different aspect ratios and volumes; moreover, the method has a higher yield and batch size than previously reported methods for producing non-spherical particles via film stretching. These particles are ideal model systems for studying the self-assembly and gel formation for systems with anisotropic shapes and interactions. We illustrate this by adding of a non-adsorbing polymer to the solvent, thereby inducing directional depletion interactions between the particles.
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http://dx.doi.org/10.1016/j.jcis.2013.10.027DOI Listing
February 2014

Probing multivalent interactions in a synthetic host-guest complex by dynamic force spectroscopy.

J Am Chem Soc 2011 Jul 24;133(28):10849-57. Epub 2011 Jun 24.

Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands.

Multivalency is present in many biological and synthetic systems. Successful application of multivalency depends on a correct understanding of the thermodynamics and kinetics of this phenomenon. In this Article, we address the stability and strength of multivalent bonds with force spectroscopy techniques employing a synthetic adamantane/β-cyclodextrin model system. Comparing the experimental findings to theoretical predictions for the rupture force and the kinetic off-rate, we find that when the valency of the complex is increased from mono- to di- to trivalent, there is a transition from quasi-equilibrium, with a constant rupture force of 99 pN, to a kinetically dependent state, with loading-rate-dependent rupture forces from 140 to 184 pN (divalent) and 175 to 210 pN (trivalent). Additional binding geometries, parallel monovalent ruptures, single-bound divalent ruptures, and single- and double-bound trivalent ruptures are identified. The experimental kinetic off-rates of the multivalent complexes show that the stability of the complexes is significantly enhanced with the number of bonds, in agreement with the predictions of a noncooperative multivalent model.
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http://dx.doi.org/10.1021/ja2016125DOI Listing
July 2011
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