Gert Desmet

• Professor (Full) at Vrije Universiteit Brussel

Tribocharging is the spontaneous charging of two bodies when released from contact. Even though its manifestation is commonplace, e.g., when rubbing a balloon across your hair, scientists find this phenomenon a mystery. The present contribution marries the conceptual ideas from chemists, materials scientists and physicists on the tribocharging of...

The perpetual curiosity of scientists to fabricate new materials with pre-engineered structures and properties lies at the heart of the overwhelming diversity of methods developed to attain large-scale assembled arrays comprising ultrafine particles. Most studies aim to use the wet assembly methods, hinging predominantly on a competing balance of t...

Using a recent generalization of the Aris dispersion method, we have derived exact analytical expressions for the long-time limit dispersion in 2-D multi-capillary packings with diffusional bridging (binary channel system). Both the plug flow and the parabolic flow case are considered. The expressions are mathematically exact over the entire range...

This study involves the systematic assessment of the effects of system configuration on dispersion, pres- sure, and retention characteristics while operating a 1500 bar UHPLC system with 2.1 mm i.d. × 100 mm long columns packed with 1.5 μm core-shell particles in isocratic and gradient mode. Altering the system configuration by changing the i.d. of...

Particle (monolayer) assembly is essential to various scientific and industrial applications, such as the fabrication of photonic crystals, optical sensors, and surface coatings. Several methods, including rubbing, have been developed for this purpose. Here, we report on the serendipitous observation that microparticles preferentially partition ont...

Monoclonal antibodies are becoming a core aspect of the pharmaceutical industry. Together with a huge therapeutic potential, these molecules come with a structural complexity that drives state-of-the-art chromatography and mass spectrometry (MS) to its limits. This article discusses the use of micro-pillar array columns in combination with mass spe...

We report on a detailed study of the injection contribution to band broadening in contemporary UHPLC-instruments, using either flow-through needle or fixed loop injection (full loop). Using on-tubing fluorescence measurements at the outlet of the injector valve, very localized and undisturbed measurements were obtained. Varying both the flow rate a...

J. Sep. Sci. 2016, 39, 4492–4501 DOI: 10.1002/jssc.201600896 Organic polymer-based monolithic stationary phases with a large and small domain size were synthesized via free-radical copolymerization. The resulting pore structures were characterized at the meso- and macroscopic levels. In addition, nanoLC experiments were conducted to establish a fun...

The mixing rate (Rϕ) is the temporal rate of increase in the solvent strength in gradient LC. The optimal Rϕ (Rϕ,Opt) for a gradient analysis is the one at which a required separation capacity and peak capacity of the analysis are obtained in the shortest time. The Rϕ,Opt of LSS (linear solvent strength) gradient LC is found in dimensionless form (...

Various designs of chips for comprehensive two-dimensional spatial liquid chromatography were investigated. The performance of these chips was initially evaluated using computational fluid dynamics (CFD). A bifurcating distributor with an angle of 140° between branches was implemented in order to achieve a homogeneous velocity field. The cross-sect...

The separation performance metrics defined in Part 1 of this series are applied to the evaluation of general separation performance of linear solvent strength (LSS) gradient LC. Among the evaluated metrics was the peak capacity of an arbitrary segment of a chromatogram. Also evaluated were the peak width, the separability of two solutes, the utiliz...

We used numerical simulations to investigate the recent observation that slip flow chromatography can obtain reduced plate heights as low as 0.032. The simulations were carried out for a 2D pillar array and a 3D face centred cubic particle stacking. We found that slip flow can only affect the mobile phase mass transfer contribution, which reduces t...

The finite length parallel zone (FPZ)-model is proposed as an alternative model for the axial- or eddy-dispersion caused by the occurrence of local velocity biases or flow heterogeneities in porous media such as those used in liquid chromatography columns. The mathematical plate height expression evolving from the model shows that the A- and C-term...

Joseph Jack Kirkland answered questions from Gert Desmet on his pioneering career in high performance liquid chromatography (HPLC).

Electrochemical anodization has been applied to grow 300 nm thick porous shell layers in 5 μm diameter silicon pillars. These pillars are positioned in a triangular grid with 2.5 μm spacing to form a pillar array columns (PAC) for liquid chromatography. The uniformity of the porous layer was assessed by determining local plate heights along the col...

In the current contribution, it is demonstrated that radial elongation of support structures in a chromatographic column has an enormous impact on the axial band broadening occurring in the column. By increasing the lateral dimension of the support structures with respect to their axial dimension, axial band broadening could be reduced up to 5 time...

We report on a numerical study wherein we modeled the influence of the segmentation ring used in the recently introduced parallel segmented flow concept. The study reconfirms that the parallel segmented flow concept can indeed improve separation performance of radially heterogeneous beds. It was however also found that the segmentation ring in itse...

The achievable separation performance of a 9 cm long pillar array channel containing 5 μm diameter silicon pillars (spacing 2.5 μm) cladded with a meso-porous silica layer with a thickness of 300 nm was investigated, interfacing the chip to a capillary LC instrument. The overall performance was evaluated by conducting gradient elution separations o...

This paper reports a novel method for separating double stranded (ds) DNA on silicon micro-pillar array chips, based on ion-pair reversed-phase (IP-RP) chromatography. Gradient elution mode has been used for on-chip DNA separation for the first time. With this mode, we have achieved separations of dsDNA fragments with larger lengths (up to 500 base...

In this work, a planar passive micromixer with small microstructured elements (SME) was studied under laminar flow conditions. The influence of the flow rate, the size and the number of elements per repeating unit on mixing was investigated. A novel 3D mixer of this type was subsequently developed and studied. Its countercurrent properties increase...

A non-porous C8 coated silicon pillar channel design is presented that allows the achievement of a high pressure and high efficiency operation for HPLC separations. Performing on-chip injection and detection and hence omitting the related dispersive sources, more than one million theoretical plates were obtained in non-retained conditions. The perf...

In this work, we report the detection of proteins by means of simultaneous fluorescence and impedance measurements in a cyclo olefin polymer (COP) chip containing an ordered pillar array column, used for reversed-phase liquid chromatography, with integrated microband gold electrodes at the end of the channel.

An integrated fluidic system has been fabricated, capable of separating a mixture of different bio-molecules into its components. It is composed of a filter and an actuator; the pressure generated by the actuator sustains the flow of the mixture through the filter. The actuator is made by stacking several layers of conductive polymer. Actuator stra...

In this work, we investigated the effect of microreactor mixing units on crystal sizes and crystal size distribution (CSD) during barium sulfate crystallization. A cheap and mass production compatible fabrication scheme was developed for PMMA micromixing devices, using a milling robot capable of generating features down to 200 μm. A drastic improve...

The ion-pair reversed phase (IP-RP) separation of short, similarly sized, double stranded (ds) DNA strains is demonstrated in a functionalized silicon pillar array channel with 1 μm flow-through pores. Using distribution zones and embedded sidewall regions optimized through computational fluid dynamics simulations, 3 nl DNA sample volumes could be...

The first in a series of interviews where rising research stars interview important figures from the world of chromatography kicks off with Gert Desmet from the Free University of Brussels talking to John Knox.

This article investigates the different methods that can be used to compare the performance of liquid chromatography (LC) columns to assess the advantage of using them at high pressures and/or high temperatures. The main focus is on the kinetic plot method. This method, which is based on two simple equations, allows the user to transform the more c...

This article reveals the first liquid chromatography (LC) separations performed on a microfabricated pillar array column under pressure-driven conditions. The pillars were non-porous and produced using a Bosch-type deep reactive ion etch (DRIE) to pattern the surface of a silicon wafer and had a diameter of approximately 5 μm. Two different packing...

Goal Design of an optical system used for miniaturized fluid-chromatographic experiments chromatography = chemical analysis technique used for the separation, identification and quantification of different components of an unknown mixture examples: tracing pesticides in drinking water; tracing steroids in blood plasma

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

This paper presents the experimental investigation of the concept of friction-induced vibrations observed in small-scale mechanical systems. A mesoscopic flat-on-flat tribotester, simulating as close as possible the behaviour of a microfluidic device, was designed and built and sliding tests on polyamide materials sliding on steel were performed in...

Hybridization on microarray slides is a very slow process. The transport of target molecules towards the immobilized probe spots occurs solely by molecular diffusion and as a result, microarray analyses require overnight incubation and are highly inefficient in terms of capture rate and detection limit. To overcome this diffusion limitation, severa...

Shear-force methods are an alternative to pressure- and voltage-gradient methods.

The authors discuss the application of a novel method (shear-driven chromatography) to propel mobile phase in high-resolution/high-speed liquid chromatography, and so attempt to overcome the pressure- and voltage-drop limitations of both high performance liquid chromatography and capillary electrochromatography. Also discussed are the challenges fa...

We explored the use of microlenses in commercial and miniaturized low-cost detection systems for the analysis of fluorescence in DNA microarrays. We investigated through simulations the properties of trans-and epi-illumination detection configurations and analyzed how microlenses can increase the detection efficiency. We fabricated microlenses by m...