A5089339557- Electrowetting and Microfluidic Technologies
- Electrostatics and Colloid Interactions
- Microfluidic and Bio-sensing Technologies
- Microfluidic and Capillary Electrophoresis Applications
- Electrochemical Analysis and Applications
- Electrohydrodynamics and Fluid Dynamics
- Surfactants and Colloidal Systems
- Nanopore and Nanochannel Transport Studies
- Orbital Angular Momentum in Optics
- Near-Field Optical Microscopy
- Spectroscopy and Quantum Chemical Studies
- Electrophoretic Deposition in Materials Science
- Digital Holography and Microscopy
- Quantum Dots Synthesis And Properties
- Characterization and Applications of Magnetic Nanoparticles
- Analytical Chemistry and Sensors
- Photoacoustic and Ultrasonic Imaging
- Mechanical and Optical Resonators
- Optical Coherence Tomography Applications
- Extracellular vesicles in disease
- Micro and Nano Robotics
- Migration, Policy, and Dickens Studies
- Gold and Silver Nanoparticles Synthesis and Applications
- Electrical and Bioimpedance Tomography
- Minerals Flotation and Separation Techniques
Ghent University
2015-2025
Philips (Belgium)
2008
Cell-derived membrane vesicles that are released in biofluids, like blood or saliva, emerging as potential non-invasive biomarkers for diseases, such cancer. Techniques capable of measuring the size and concentration directly biofluids urgently needed. Fluorescence single particle tracking microscopy has doing exactly by labelling with a fluorescent label analysing their Brownian motion biofluid. However, an unbound dye biofluid can cause high background intensity strongly biases...
The Poisson-Nernst-Planck equations describe the dynamics of charge transport in an electric field. Although they are relevant many applications, a general solution is not known and several aspects well understood. In situations nonlinear effects arise for which no analytical description available. this work, we investigate planar device on application voltage step. We derive expressions dynamical behavior four extreme cases. ``geometry limited'' regime, applicable at high voltages low...
By measuring the stable charge on oil drops in air, Millikan demonstrated discrete nature of electric charge. We extend his approach to solid-liquid interfaces, and focus dynamics fluctuations. Our measurements are accurate fast enough observe changes one elementary Experiments over thousands seconds yield information about electrochemical reactions, relevant for physicochemical biological systems. As an example, we study (dis)charging processes colloidal particles a nonpolar liquid.
Liquid crystalline polymers are attractive materials for untethered miniature soft robots. When they contain azo dyes, acquire light-responsive actuation properties. However, the manipulation of such photoresponsive at micrometer scale remains largely unexplored. Here, uni- and bidirectional rotation speed control polymerized azo-containing chiral liquid photonic microparticles powered by light is reported. The these polymer particles first studied in an optical trap experimentally...
An improved small-circle scanning fluorescence correlation spectroscopy (sFCS) technique is introduced by combining acousto-optical laser with fitting the autocorrelation function in frequency domain. The validated using both simulation and experimental data on various fluorescent nanoparticles, including polystyrene beads, CdSe/CdS quantum dots, lipid nanoparticles. Then, sFCS method used to investigate adsorption of in-house synthesized poly(2-guanidinoethyl methacrylate) (PGUMA) polymers...
Anti-Brownian electrokinetic trapping enables the confinement of individual nanoparticles in liquids by applying electric fields. This technique facilitates long-term observation nanoscopic objects, allowing for detailed studies their physical, chemical, and biomolecular properties. However, this method has been largely restricted to that can be visualized photoluminescence. While some techniques avoid fluorescent labeling using dark-field or interferometric scattering microscopy, they are...
We have succeeded in determining the charge of individual colloidal particles with resolution higher than elementary charge. The number charges on a particle is obtained from analysis optical tracking data weakly charged silica spheres an electric field nonpolar medium. also yields accurate value size. Measurement as function time reveals events which loses or gains due to ionization recombination processes at surface.
Surfactants such as Aerosol OT (AOT) are commonly used to stabilize and electrically charge nonpolar colloids in devices electronic ink displays. The electrical behavior of is strongly influenced by the presence charged inverse micelles, formed excess surfactant that does not cover particles. micelles results increased conductivity solution, affecting both energy consumption device its switching characteristics. In this work, we use transient current measurements investigate properties...
Semiconductor nanorods mainly absorb and emit light with the electric field along axis of rods, it is therefore important to align a preferred direction. The homogeneous deposition aligned on large substrates interesting for size applications such as solar cells OLEDs. In this work, we present fast versatile method alignment from colloidal suspension. based low-cost dip-coating procedure during which an alternating applied. accumulation, orientation, polarized fluorescence verified by AFM...
Transient current measurements in response to a voltage step can reveal lot of information about the nature, origin, and properties electrically charged species nonpolar media. In situations where influence charges on electric field be neglected, interpretation is straightforward. However, this condition not fulfilled many applications. This work provides an approximate analytical description, illustrated by simulations, for cases which contribution charge density comparable magnitude...
Charged inverse micelles play an important role in the electrical charging and electrodynamics of nonpolar colloidal dispersions relevant for applications such as electronic ink displays liquid toner printing. This review examines properties behavior charged microscale devices absence particles. It is discussed how charge liquids stabilized conductivity depends on micelle size, water content ionic impurities. Frequently used surfactant systems are investigated with emphasis aerosol-OT (AOT)...
Transient current measurements are used to characterize a wide variety of charge carriers in nonpolar liquids. The transient method allows us obtain both the concentration and mobility therefore also hydrodynamic radius using Stokes' law. In this article, five different surfactants dodecane investigated: OLOA11K, Solsperse13940, Span80, Span85, AOT. We show that types currents observed depending on size inverse micelles. For large micelles such as for measurement is straightforward because...
The presence of charges in nonpolar liquids is usually neglected. However, some applications, they have important effects. In this work, an analytical description given for the dynamics diffuse double layers when a voltage step order kT∕e applied. Part result expression current, which consistent with current measurements on and other works. higher voltages, we observe briefly discuss nonlinear From both at high low can obtain same properties liquid.
The Poisson-Boltzmann (PB) equation is widely used to calculate the interaction between electric potential and distribution of charged species. In case a symmetrical electrolyte in planar geometry, Gouy-Chapman (GC) solution generally presented as analytical PB equation. However, we demonstrate here that this GC assumes presence bulk region with zero field, which not justified microdevices. order extend range validity, obtain complete numerical equation, supported approximations. For low...
Surfactant molecules in a non-polar liquid form charged and uncharged inverse micelles. When potential difference is applied over the mixture, micelles drift towards electrode with opposite polarity. The motion of charges associated transient current, which can be measured an external circuit. In this paper, currents steady state charge densities are described analytically different ranges parameter values (applied voltage, density, device thickness, mobility,...). generation additional...
The fundamental principle for electrophoresis, the motion of a charged particle in solution driven by an applied electric field, is well understood. But experimental measurements electrophoretic retardation force, one those responsible have been scarce and equivocal. Now Belgian group develops creative new approach to control source retardation---the counterion cloud surrounding particle---by gradual depletion makes unambiguous measurement force.
We analyze thermal charging in additive-free colloidal CdSe quantum dot (QD) dispersions by means of the transient electric current resulting from a voltage step applied across QD dispersion. On basis initial and total charge separated, we find that dispersion behaves as 1:1 electrolyte where equal fractions QDs carry single positive or negative charge. This conclusion is confirmed more detailed fitting using Nernst−Planck−Poisson equations. Using equilibrium thermodynamics, relate fraction...
We have compared optical tracking and electric current measurements to study the electrokinetics of colloidal particles in nonpolar media containing charged inverse micelles. Particle trajectories are measured response a voltage step, revealing spatial temporal variations field when space-charge layers created by The particle good agreement with simulations analytical approximations based on drift diffusion charges. Electrohydrodynamic effects observed at high concentrations micelles...
Colloidal particles that are dissolved in a liquid can become charged by preferential adsorption or dissociation of surface molecules. The assumption constant charge density leads to particle is proportional the square radius. Recent experiments however have shown number cases linearly its size. We present simple model for charging colloidal leading linear relation between and size framework mean-field Poisson-Boltzmann theory. based on molecules, combination with large concentration...
Transient currents of electrolytes in response to a voltage step can reveal lot about the behavior charges present an electrolyte. In this paper, with high ionic strength are considered. limit small steps, interpretation is straightforward as equations describing transient be linearized. However, when ion concentrations and steps order $kT∕q$ considered, we find higher-order effects that occur simultaneously diffuse double layer charging. case, diffusion coupled because screening field,...