Optimizing Tris(2-Carboxyethyl)phosphine and Mercaptohexanol Concentrations for Thiolated Oligonucleotide Immobilization on Platinum Electrodes in Microfluidic Platforms.

In this study, we propose a strategy to explore the impact of the proportion of tris(2-carboxyethyl)phosphine (TCEP) and 6-mercaptohexanol (MCH) on the efficiency of oligonucleotide functionalization on PDMS microfluidic channels equipped with pairs of homemade microfabricated platinum microelectrodes. We identified an optimal concentration of these compounds that enables the effective orientation and distribution of probes, thereby facilitating subsequent target hybridization. The experiment included optimizing sample injection into microfluidic channels.

Influence of Lanthanum on Stern Layer Conductance in the Nanochannel.

In this report, high-frequency electric impedance spectroscopy was performed to investigate ionic transport through nanochannels. Special attention was focused on (i) conductance behaviors depending on the role of cation valence in three background electrolytes (XCln): monovalent 1-1 (K and Cl), divalent 2-1 (Mg and 2Cl), and trivalent 3-1 (La and 3Cl), (ii) the effects of proton and bicarbonate ions on bulk and surface conductance, and (iii) the connected microchannel dimension (surface/height ratio aspect) within the nanochannel apparent conductance. The results highlight a net quantitative increase in surface silanol density and a strong decrease in surface ionization degree when lanthanum cations are employed.

Predicting ion concentration polarization and analyte stacking/focusing at nanofluidic interfaces.

We report on the investigation of electropreconcentration phenomena in micro-/nanofluidic devices integrating 100 μm long nanochannels using 2D COMSOL simulations based on the coupled Poisson-Nernst-Planck and Navier-Stokes system of equations. Our numerical model is used to demonstrate the influence of key governing parameters such as electrolyte concentration, surface charge density, and applied axial electric field on ion concentration polarization (ICP) dynamics in our system. Under sufficiently extreme surface-charge-governed transport conditions, ICP propagation is shown to enable various transient and stationary stacking and counter-flow gradient focusing mechanisms of anionic analytes.

A compact integrated microfluidic oxygenator with high gas exchange efficiency and compatibility for long-lasting endothelialization.

We have developed and tested a novel microfluidic device for blood oxygenation, which exhibits a large surface area of gas exchange and can support long-term sustainable endothelialization of blood microcapillaries, enhancing its hemocompatibility for clinical applications. The architecture of the parallel stacking of the trilayers is based on a central injection for blood and a lateral injection/output for gas which allows significant reduction in shear stress, promoting sustainable endothelialization since cells can be maintained viable for up to 2 weeks after initial seeding in the blood microchannel network. The circular design of curved blood capillaries allows covering a maximal surface area at 4 inch wafer scale, producing high oxygen uptake and carbon dioxide release in each single unit.

Electropreconcentration diagrams to optimize molecular enrichment with low counter pressure in a nanofluidic device.

Concentration polarization (CP)-based focusing electrokinetics nanofluidic devices have been developed in order to simultaneously detect and enrich highly diluted analytes on-a-chip. However, stabilization of focal points over long time under the application of the electric field remains as a technical bottleneck. If pressure-assisted preconcentration methods have been proposed to stabilize propagating modes at low inverse Dukhin number , these recent protocols remain laborious for optimizing experimental parameters.

Logic digital fluidic in miniaturized functional devices: Perspective to the next generation of microfluidic lab-on-chips.

Microfluidics has emerged following the quest for scale reduction inherent to micro- and nanotechnologies. By definition, microfluidics manipulates fluids in small channels with dimensions of tens to hundreds of micrometers. Recently, microfluidics has been greatly developed and its influence extends not only the domains of chemical synthesis, bioanalysis, and medical researches but also optics and information technology.

Localized Mechanical Stress Promotes Microtubule Rescue.

Microtubule dynamics rely on the properties of tubulin and are regulated by microtubule-associated proteins. GTP-tubulin assembles into hollow polymers, which can depolymerize upon GTP hydrolysis. Depolymerizing microtubules may stop shrinking and resume growth.

Large area graphene nanomesh: an artificial platform for edge-electrochemical biosensing at the sub-attomolar level.

Recent advances in large area graphene growth have led to tremendous applications in a variety of areas. The graphene nanomesh with its tunable band-gap is of great interest for both fundamental research, to explore the effect of edges on both the 2D electrical conduction and its electrochemical behavior, and applications such as nanoelectronic devices or highly sensitive biosensors. Here, we report on the fabrication of a large surface graphene nanomesh by nanoimprint lithography (NIL) to produce controlled artificial edges.

Determination of the isomeric forms proportion of fluorogenic naphthalene-2,3-dicarboxaldehyde in a binary mixture of water:methanol using electrochemical methods.

The electrochemical response of the fluorogenic label naphthalene-2,3-dicarboxyaldehyde (NDA) in a binary mixture of water/methanol was characterized with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) electrochemical techniques. Naphthalene-2,3-dicarboxyaldehyde does exist in three isomeric forms in aqueous solution: the unhydrated dialdehyde (DA), the acyclic monohydrated (MA) and the cyclic hemiacetal (HAC). The study underlines that the proportion of each of them varies according to the working pH.

Electrochemiluminescence on-a-chip: towards a hand-held electrically powered optofluidic source.

We report a microfluidic platform that integrates several parallel optical sources based on electrochemiluminescence (ECL) of 9,10-diphenylanthracene (DPA) as luminophore agent. The annihilation of DPA radicals provides a low wavelength emission at λ=430 nm in the blue-visible range. By varying the distance between electrodes for each ECL integrated source, this glass/PDMS/glass platform enabled a systematic investigation of the main electrochemical parameters involved in ECL.

Improved electrochemical detection of a transthyretin synthetic peptide in the nanomolar range with a two-electrode system integrated in a glass/PDMS microchip.

An alternative to a three-electrode set-up for electrochemical detection and analysis in microfluidic chips is described here. The design of the electrochemical sensor consists of the surface of the glass substrate covered with a PDMS block which bears the microfluidic channels. A band microelectrode which acts as a working electrode surrounded by a large counter electrode is obtained at the micrometric level to propose a simple and efficient sensing area for on-a-chip analysis.

A microdevice for parallelized pulmonary permeability studies.

We describe a compartmentalized microdevice specifically designed to perform permeability studies across a model of lung barrier. Epithelial cell barriers were reproduced by culturing Calu-3 cells at the air-liquid interface (AIC) in 1 mm² microwells made from a perforated glass slide with an embedded porous membrane. We created a single basolateral reservoir for all microwells which eliminated the need to renew the growth medium during the culture growth phase.

Investigating of labelling and detection of transthyretin synthetic peptide derivatized with naphthalene-2,3-dicarboxaldehyde.

Labelling and detection of a synthetic peptide (PN) mimicking a tryptic fragment of interest for the diagnosis of familial amyloidal polyneuropathy have been investigated optically and electrochemically. We decided to covalently label naphtalene-2,3-dicarboxyaldehyde (NDA), a fluorogenic and electroactive molecule on PN. First, the optimization of the labelling chemical reaction was performed by capillary electrophoresis coupled with laser induced fluorescence detection (CE-LIF).

Pressure-assisted selective preconcentration in a straight nanochannel.

We investigate the preconcentration profiles of a fluorescein and bovine serum albumin derivatized with this fluorescent tag in a microfluidic chip bearing a nanoslit. A new preconcentration method in which a hydrodynamic pressure is added to both electroosmotic and electrophoretic contributions is proposed to monitor the location of the preconcentration frontline. A simple predictive model of this pressure-assisted electropreconcentration is proposed for the evolution of the flow profile along this micro/nano/microfluidic structure.

Computational study of velocity profile obtained in microfluidic channel bearing a fluidic transistor: toward highly resolved electrophoretic separation.

The present work is a computational study of velocity profiles in microfluidic channels bearing field flow effect transistors (FFET). In particular, this work investigates perturbations and distortions of the sample band during electrophoretic transport in a rectangular separation channel. The EOF heterogeneity and its induced pressure render the predictions of the analytical performances rather complex.

Self-assembled titanium calcium oxide nanopatterns as versatile reactive nanomasks for dry etching lithographic transfer with high selectivity.

We report the simple preparation of ultra-thin self-assembled nanoperforated titanium calcium oxide films and their use as reactive nanomasks for selective dry etching of silicon. This novel reactive nanomask is composed of TiO(2) in which up to 50% of Ti was replaced by Ca (Ca(x)Ti(1-x)O(2-x)). The system was prepared by evaporation induced self-assembly of dip-coated solution of CaCl(2), TiCl(4) and poly(butadiene-block-ethylene oxide) followed by 5 min of thermal treatment at 500 °C in air.

A nanoliter-scale open chemical reactor.

An open chemical reactor is a container that exchanges matter with the exterior. Well-mixed open chemical reactors, called continuous stirred tank reactors (CSTR), have been instrumental for investigating the dynamics of out-of-equilibrium chemical processes, such as oscillations, bistability, and chaos. Here, we introduce a microfluidic CSTR, called μCSTR, that reduces reagent consumption by six orders of magnitude.

Photonic crystal patterning of luminescent sol-gel films for light extraction.

Structured luminescent thin films are investigated in the context of improved light extraction of phosphors for solid-state-lighting applications. Thin films composed of a sol-gel titania matrix doped with europium chelates are studied as a model system. These films, patterned with a square photonic lattice by soft nanoimprint lithography, are characterized by angle-resolved fluorescence.

λ³/1000 plasmonic nanocavities for biosensing fabricated by soft UV nanoimprint lithography.

Arrays of plasmonic nanocavities with very low volumes, down to λ(3)/1000, have been fabricated by soft UV nanoimprint lithography. Nearly perfect omnidirectional absorption (3-70°) is demonstrated for the fundamental mode of the cavity (λ ≃ 1.15 μm).

Ionic and mass transport in micro-nanofluidic devices: a matter of volumic surface charge.

The shape and the surface charge of microchannels are critical parameters for ionic and mass transport in microfluidic systems. A great number of studies and developments have been carried out in order to optimize these features separately. We propose to consider them together within a new fundamental parameter for microfluidics, that we named the Volumic Surface Charge (VSC), which is the ratio of the surface charge to the section height in planar microchannels.

Electropreconcentration with charge-selective nanochannels.

We report on the systematic investigation of electropreconcentration phenomena in hybrid micro/nanofluidic devices. The competition between the electroosmotic dragging force and the highly nonlinear electrophoretic forces induced by the polarization effect is responsible for four preconcentration regimes within such structures that can arise at both cathodic and anodic sides of the nanochannel. Numerical calculations on the spatiotemporal concentration of charged molecules confirm such a classification, showing a general agreement with the reported experimental data at low and moderate ionic strengths.