Extending the microfabrication and particle handling toolbox for the development of ordered chromatography columns

Improving the order of the beads packed in a liquid chromatography column would practically translate into a situation where for instance a researcher in the biomedical field analyzing a biological sample (e.g. a cancer cell) would be able to identify a multifold more molecules (eg proteins), using one and the same, yet optimized liquid chromatography column. The present work investigates a number of new techniques to produce order columns suitable for chromatography. These techniques include a combination of deep reactive ion etching in silicon with mechanical rubbing and other particle handling methods to fill arrays of micro-pockets with either single particles or a well-defined multiple. A broad range of particle handling methods has been explored and has led to a fully optimized procedure involving a novel combination of micro-structured polydimethylsiloxane and wet manual rubbing. During the work, the power of silicon micromachining has also been explored to produce perfectly ordered columns for gas chromatography

Optimisation des performances des micro-colonnes de type multicanaux en GC et application en GC bidimensionnelle (GC×µGC)

National audienc

Optimization of GC columns with radially-elongated pillars with different coatings as second dimension of comprehensive two-dimensional gas chromatography (GC×µGC).

National audienc

Optimisation des performances des micro-colonnes de type multicanaux en GC et application en GC bidimensionnelle (GC×µGC)

National audienc

Optimization of GC columns with radially-elongated pillars with different coatings as second dimension of comprehensive two-dimensional gas chromatography (GC×µGC).

National audienc

Particle assembly via wet PDMS rubbing in pre-patterned silicon substrates for the fabrication of ordered particle arrays in microfluidic devices

Here, a wet rubbing method using a patterned rubbing tool is proposed for filling arrays of interconnected micromachined pockets with individual microspheres on rigid, uncoated silicon substrates without damaging the substrate or particles. We show that 5-10 µm silica and polystyrene particles can be assembled using this method, with a filling ratio (FR) of 99.5%. These particle arrays are entirely sunken in the structures that may be placed in a sealed environment, opening routes to microfluidic applications, such as liquid chromatography or catalysis.</p

Wafer-Scale Particle Assembly in Connected and Isolated Micromachined Pockets via PDMS Rubbing

The present contribution reports on a study aiming to find the most suitable rubbing method for filling arrays of separated and interconnected micromachined pockets with individual microspheres on rigid, uncoated silicon substrates without breaking the particles or damaging the substrate. The explored dry rubbing methods generally yielded unsatisfactory results, marked by very large percentages of empty pockets and misplaced particles. On the other hand, the combination of wet rubbing with a patterned rubbing tool provided excellent results (typically <1% of empty pockets and <5% of misplaced particles). The wet method also did not leave any damage marks on the silicon substrate or the particles. When the pockets were aligned in linear grooves, markedly the best results were obtained when the ridge pattern of the rubbing tool was moved under a 45° angle with respect to the direction of the grooves. The method was tested for both silica and polystyrene particles. The proposed assembly method can be used in the production of medical devices, antireflective coatings, and microfluidic devices with applications in chemical analysis and/or catalysis

Optimisation des performances des micro-colonnes de type multicanaux en GC et application en GC bidimensionnelle (GC×µGC)

National audienc

Structured Microgroove Columns as a Potential Solution to Obtain Perfectly Ordered Particle Beds

We report on a novel concept to produce ordered beds of spherical particles in a suitable format for liquid chromatography. In this concept, spherical particles are either positioned individually (single-layer column) or stacked (multi-layer column) in micromachined pockets that form an interconnected array of micro-grooves acting as a perfectly ordered chromatographic column. As a first step towards realizing this concept, we report on the breakthrough we realized by obtaining a solution to uniformly fill the micro-groove arrays with spherical particles. We show this can be achieved in a few sweeps using a dedicated rubbing approach wherein a particle suspension is manually rubbed over a silicon chip. In addition, numerical calculations of the dispersion in the newly introduced column format have been carried out and demonstrate the combined advantage of order and reduced flow resistance the newly proposed concept has over the conventional packed bed. For fully-porous particles and a zone retention factor of k’’ = 2, the hmin decreases from hmin = 1.9 for the best possible packed bed column to around hmin =1.0 for the microgroove array, while the interstitial velocity-based separation impedance Ei (a direct measure for the required analysis time) decreases from 1450 to 200. The next steps will focus on the removal of occasional particles remaining on the sides of the micro-pockets, the addition of a cover substrate to seal the column and the subsequent conduction of actual chromatographic separations

Evaluation of Gas Chromatography Columns with Radially Elongated Pillars as Second-Dimension Columns in Comprehensive Two-Dimensional Gas Chromatography

The present study investigated the use of a dedicated gas chromatography (GC) column (L = 70 cm, 75 μm deep, and 6.195 mm wide) with radially elongated pillars (REPs) as the second column in a comprehensive two-dimensional gas chromatography (GC × μGC) system. Three stationary phases [apolar polydimethylsiloxane (PDMS), medium polar room-temperature ionic liquid (RTIL) based on monocationic phosphonium, and polar polyethylene glycol (PEG-1000)] have been coated using the static method at constant pressure or using an original vacuum pressure program (VPP) from 400 to 4 mbar. The best efficiency reached up to N = 62,000 theoretical plates for a film thickness of 47 nm at 100 °C for an iso-octane peak (k = 0.16) at an optimal flow rate of 4.8 mL/min. The use of the VPP improved the efficiency by approximately 15%. Efficiencies up to 28,000 and 47,000 were obtained for PEG-1000 and RTIL, respectively. A temperature-programmed separation of a mixture of 11 volatile compounds on a PDMS-coated chip was obtained in less than 36 s. The PDMS-, PEG-1000-, and RTIL-coated chips were tested as the second column using a microfluidic reverse fill/flush flow modulator in a GC × μGC system. The REP columns were highly compatible with the operating conditions in terms of flow rate and with more than 30,000 plates for the iso-octane peak. Moreover, a commercial solvent called white spirit containing alkanes and aromatic compounds was injected in three sets of columns in normal and reverse modes, demonstrating the great potential of the chip as a second-dimension separation column