The extensive application of monolithic columns for HPLC is severely hindered by a lack of column-to-column reproducibility. EMμ(Electroactive Monolithic μChip) is a new concept that solves the significant reproducibility problems, as well as allowing miniaturization and improving overall efficiency through electrochemically controlled dynamic separations. This novel μchip has a micro-structured monolith fabricated from intelligent, electroactive polymer. By application of a specific potential, conducting polymers such as polyaniline (PANI) can be reproducibly grown and readily fine-tuned in terms of porosity, hydrophobicity an

d ionic capacity. This unique chip provides for an Electroac

tive Monolithic μchip capable of multi-dimensional chromatographic separations.

The monolith microstructuring (provided by templating) wi

ll provide reproducibility and improve efficiency by decre

asing the A-term of the Van Deemter equation. Furthermore, the use of these intelligen t materials will enable gradient control and redox reaction s to be exploited during

separations of large biomolecules

Galineau, Jeremy

Morrin, Aoife

Smyth, Malcolm R.

White, Blánaid

DCU Online Research Access Service

Galineau, J., White, B., Smyth, M.R., Morrin, A.*, Sensors and Separations Group, NCSR, School of Chemical Sciences, Dublin City University, Dublin 9; blanaid.white@dcu.ieElectroactive Monolithic µChips Based on Nanostructured PolyanilineChip DesignConceptThe aim of this project was to create a highly reproducible micro-structured monolithicstationary phase within a commercial glass µchip, using the following steps:• assemble a reproducible template within the separation channel:• polymerise the monolith through the template;• sacrifice the template without damaging the monolith.Polystyrene (PS) beads were used as the template, with PANI fabricated electrochemically toform the monolithic stationary phase.PS beads were synthesised according to Shim et al. (J. App. Poly. Sc., 71 (13) 2259).For this synthesis, di-vinyl-benzene (DVB) was used as a cross linking agent duringpolymer synthesis. Increasing DVB concentration was found to increase the stabilityand rigidity of the resulting beads, and therefore decrease their solubility (left). Bydecreasing the DVB concentration to 0.4% during synthesis, PS beads were formed,which were sufficiently rigid, monodispersed and spherical to be used as templatingscaffolds, but which readily dissolved in toluene, ensuring that the PS nanostructurecould be sacrificed when required (shown on right).Development of a dissolvable PS bead templateThe extensive application of monolithic columns for HPLC is severely hindered by a lack of column-to-column reproducibility. EMµ (ElectroactiveMonolithic µChip) is a new concept that solves the significant reproducibility problems, as well as allowing miniaturization and improving overallefficiency through electrochemically controlled dynamic separations. This novel µchip has a micro-structured monolith fabricated from intelligent,electroactive polymer. By application of a specific potential, conducting polymers such as polyaniline (PANI) can be reproducibly grown andreadily fine-tuned in terms of porosity, hydrophobicity and ionic capacity. This unique chip provides for an Electroactive Monolithic µchip capableof multi-dimensional chromatographic separations.The monolith microstructuring (provided by templating) will provide reproducibility and improve efficiency by decreasing the A-term of the VanDeemter equation. Furthermore, the use of these intelligent materials will enable gradient control and redox reactions to be exploited duringseparations of large biomolecules.The glass microfluidic chip (Micronit) has cross-shaped channel dimensions 110 µm x 50 µm(width x length). To electrochemically grow the stationary phase, a 20 mm length of the mainchip channel was gold-sputtered to serve as the working electrode. PS was packed in anordered fashion into the main channel via capillary forces, using surface energy directedevaporation-induced self assembly. PANI was electrochemically deposited to the workingelectrode via a three-electrode cell. The auxiliary electrode and C4D detector were etched intothe printed circuit board. The mask used to etch the PCB is shown on the right.Chip BondingChip bonding was achieved viathe pressure sensitive adhesive(PSA) layer. Fluidic connectionswere made through apolydimethylsiloxane (PDMS)gasket to ensure leakage-freeconnections. The etched PCB wascovered with epoxy glue. The gluewas then ground until copperelectrodes were revealed in orderto obtain a smooth, flat surface.Finally, pressure was maintainedby screwing the whole system in acustom made chip holder.Microstructured PANI monolithic stationary phaseInverse opal PANI structures were obtained by electrochemically growing PANIthrough a sacrificial PS template. PS opals were grown at 40ºC using 1 % (w/v), 1 µmPS beads suspension. PANI was then grown potenstiostatically at +0.9 V vs Ag/AgCl.After removing the PS template using toluene, a typical inverse opal PANI structurewas observed. The observed structure is ordered in 3-dimensions, potentiallyproviding a new way for improving chip-to-chip reproducibility of monolithic stationaryphases.Increasing the surfactant concentration in the original PS beads suspensions increasedthe zeta potential of the PS beads (data not shown). When rewetting the template withthe monomer solution, the electrostatic repulsion between the beads disorganised thetemplate (which were PS opals in all cases). Thus by increasing the surfactantconcentration, the microstructure of the polymer can be tailored from inverse opals torandom hollow spheres. (Scale bars 100 µm)Direction of polymerisation to ensure pore inter-connectivityIncreasing surfactant concentrationConclusion A micro-structured monolithic stationary phase has been fabricated from intelligent electroactive polymer. The electropolymerisation process allowedgood reproducibility of the polymers physico-chemical properties. It has been shown that the surfactant concentration in the the PS beads could be tuned to optimisethe final PANI structures. Finally, highly ordered stationary phase structures were formed within the microfluidic channel.

Electroactive monolith μchips based on nanostructured polyaniline

The extensive application of monolithic columns for HPLC is severely hindered by a lack of column-to-column reproducibility. EMμ(Electroactive Monolithic μChip) is a new concept that solves the significant reproducibility problems, as well as allowing miniaturization and improving overall efficiency through electrochemically controlled dynamic separations. This novel μchip has a micro-structured monolith fabricated from intelligent, electroactive polymer. By application of a specific potential, conducting polymers such as polyaniline (PANI) can be reproducibly grown and readily fine-tuned in terms of porosity, hydrophobicity an\ud
d ionic capacity. This unique chip provides for an Electroac\ud
tive Monolithic μchip capable of multi-dimensional chromatographic separations.\ud
The monolith microstructuring (provided by templating) wi\ud
ll provide reproducibility and improve efficiency by decre\ud
asing the A-term of the Van Deemter equation. Furthermore, the use of these intelligen t materials will enable gradient control and redox reaction s to be exploited during\ud
separations of large biomolecules

Name not available

http://doras.dcu.ie/19862/1/Poster_29_Macro_2010_%5BCompatibility_Mode%5D.pdf

Electroactive monolith μchips based on nanostructured polyaniline

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