000083856 001__ 83856
000083856 005__ 20190316233721.0
000083856 0247_ $$2doi$$a10.5075/epfl-thesis-3538
000083856 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis3538-7
000083856 02471 $$2nebis$$a5150326
000083856 037__ $$aTHESIS
000083856 041__ $$aeng
000083856 088__ $$a3538
000083856 245__ $$aTransport phenomena in nanofluidics$$bform ionic studies to proteomic applications
000083856 269__ $$a2006
000083856 260__ $$aLausanne$$bEPFL$$c2006
000083856 300__ $$a164
000083856 336__ $$aTheses
000083856 520__ $$aThis thesis explores transport phenomena in nanochannels on a chip. Fundamental nanofluidic ionic studies form the basis for novel separation and preconcentration applications for proteomic purposes. The measurements were performed with 50-nm-high 1D nanochannels, which are easily accessible from both sides by two microchannels. Nanometer characteristic apertures were manufactured in the bonded structure of Pyrex-amorphous silicon – Pyrex, in which the thickness of the amorphous silicon layer serves as a spacer to define the height of the nanochannels. The geometry of the nanometer-sized apertures is well defined, which simplifies the modeling of the transport across them. Compared to biological pores, the present nanochannels in Pyrex offer increased stability. Fundamental characteristics of nanometer-sized apertures were obtained by impedance spectroscopy measurements of the nanochannel at different ionic strengths and pH values. A conductance plateau (on a log-log scale) was modeled and measured, establishing due to the dominance of the surface charge density in the nanochannels, which induces an excess of mobile counterions to maintain electroneutrality. The nanochannel conductance can be regulated at low ionic strengths by pH adjustment, and by an external voltage applied on the chip to change the zeta potential. This field-effect allows the regulation of ionic flow which can be exploited for the fabrication of nanofluidic devices. Fluorescence measurements confirm that 50-nm-high nanochannels show an exclusion of co-ions and an enrichment of counterions at low ionic strengths. This permselectivity is related to the increasing thickness of the electrical double layer (EDL) with decreasing salt concentrations, which results in an EDL overlap in an aperture if the height of the nanochannel and the thickness of the EDL are comparable in size. The diffusive transport of charged species and therefore the exclusion-enrichment effect was described with a simple model based on the Poisson-Boltzmann equation. The negatively charged Pyrex surface of the nanometer characteristic apertures can be inversed with chemical surface pretreatments, resulting in an exclusion of cations and an enrichment of anions. When a pressure gradient is applied across the nanochannels, charged molecules are electrostatically rejected at the entrance of the nanometer-sized apertures, which can be used for separation processes. Proteomic applications are presented such as the separation and preconcentration of proteins. The diffusion of Lectin proteins with different isoelectric points and very similar compositions were controlled by regulating the pH value of the buffer. When the proteins are neutral at their pI value, the diffusion coefficient is maximal because the biomolecules does not interact electrostatically with the charged surfaces of the nanochannel. This led to a fast separation of three Lectin proteins across the nanochannel. The pI values measured in this experiment are slightly shifted compared to the values obtained with isoelectric focusing because of reversible adsorption of proteins on the walls which affects the pH value in the nanochannel. An important application in the proteomic field is the preconcentration of biomolecules. By applying an electric field across the nanochannel, anionic and cationic analytes were preconcentrated on the cathodic side of the nanometer-sized aperture whereas on the anodic side depletion of ions was observed. This is due to concentration polarization, a complex of effects related to the formation of ionic concentration gradients in the electrolyte solution adjacent to an ion-selective interface. It was measured that the preconcentration factor increased with the net charge of the molecule, leading to a preconcentration factor of > 600 for rGFP proteins in 9 minutes. Such preconcentrations are important in micro total analysis systems to achieve increased detection signals of analytes contained in dilute solutions. Compared to cylindrical pores, our fabrication process allows the realization of nanochannels on a chip in which the exclusion-enrichment effect and a big flux across the nanometer-sized aperture can be achieved, showing the interest for possible micro total analysis system applications. The described exclusion-enrichment effect as well as concentration polarization play an important role in transport phenomena in nanofluidics. The appendix includes preliminary investigations in DNA molecule separation and fluorescence correlation spectroscopy measurements, which allows investigating the behavior of molecules in the nanochannel itself.
000083856 6531_ $$aconcentration polarization
000083856 6531_ $$aconductance plateau
000083856 6531_ $$aelectrical double layer
000083856 6531_ $$aexclusion-enrichment effect
000083856 6531_ $$aionic strength
000083856 6531_ $$amicro total analysis system
000083856 6531_ $$ananochannel
000083856 6531_ $$ananofluidics
000083856 6531_ $$ananoslit
000083856 6531_ $$apreconcentration
000083856 6531_ $$apermselectivity
000083856 6531_ $$aproteomics
000083856 6531_ $$aseparation
000083856 6531_ $$asurface charge density
000083856 6531_ $$asurface pretreatment
000083856 6531_ $$azeta potential
000083856 6531_ $$aconcentration de polarisation
000083856 6531_ $$adensité de charge de surface
000083856 6531_ $$adouble couche électrique
000083856 6531_ $$aeffet de l'exclusion et de l'enrichissement
000083856 6531_ $$aforce ionique
000083856 6531_ $$amicro total analysis system
000083856 6531_ $$ananocanal
000083856 6531_ $$ananofluidique
000083856 6531_ $$ananoslit
000083856 6531_ $$apermsélectivité
000083856 6531_ $$aplateau de conductance
000083856 6531_ $$apotentiel zeta
000083856 6531_ $$apréconcentration
000083856 6531_ $$aprétraitement de surface
000083856 6531_ $$aprotéomique
000083856 6531_ $$aséparation
000083856 700__ $$0240441$$aSchoch, Reto Bruno$$g156273
000083856 720_2 $$0240219$$aRenaud, Philippe$$edir.$$g107144
000083856 8564_ $$s5900652$$uhttps://infoscience.epfl.ch/record/83856/files/EPFL_TH3538.pdf$$yTexte intégral / Full text$$zTexte intégral / Full text
000083856 909C0 $$0252064$$pLMIS4$$xU10324
000083856 909CO $$ooai:infoscience.tind.io:83856$$pthesis$$pthesis-bn2018$$pDOI$$pSTI$$qDOI2$$qGLOBAL_SET
000083856 918__ $$aSTI$$bSTI-SMT
000083856 919__ $$aLMIS4
000083856 920__ $$a2006-6-9$$b2006
000083856 970__ $$a3538/THESES
000083856 973__ $$aEPFL$$sPUBLISHED
000083856 980__ $$aTHESIS