Derivatization of Plastic Microfluidic Devices with Polyelectrolyte Multilayers Susan L. R. Barker, Michael J. Tarlov, Micheal Branham, Jay Xu, William MacCrehan, Michael Gaitan, Laurie E. Locascio

Overview Fabrication of plastic microdevices Characterization of surface chemistry Derivatization with polyelectrolyte multilayers –EOF mobility –Separations and selectivity –Control of flow direction

Silicon Template Imprinting Silicon Template SEM of silicon template Raised silicon used to imprint channels Si Plastic Imprinted PlasticSEM of imprinted channel

Room Temperature Imprinting plastic press template press Al block Xu, J.; Locascio, L. E.; Lee, C. S. Anal. Chem. 2000, 72, Plastic Substrate PDMS Lid

EOF Comparison * Huang, X.; Gordon, M.; Zare, R.N. Anal. Chem. 1988, 60, § Locascio, L., Perso, C., Lee, C. J. Chrom., A 1999, 857,

Imprinted channel treated with carboxylate-reactive dye Brightfield ImageFluorescence Image Chemical Mapping Microchannel floor is uncharged Microchannel walls have high charge EOF originates from wall

Polyelectrolyte Multilayers Facile construction Reproducible surface chemistry Control of EOF mobility Control of flow direction Plastic Substrate PEM

Polyelectrolytes SO 3 - Na + n HCl CH 2 NH 2 CH 2 CH n Polystyrene sulfonate Poly(allylamine hydrochloride) 15 min. treatment of channel with 1 M NaOH at 50-60°C 20 min. treatment with polycation, pH 9, 0.5M NaCl 20 min. treatment with polyanion, pH 9, 0.5M NaCl Alternating 5 min. treatments with positive and negative polyelectrolytes to create desired total number of layers Chen, W.; McCarthy, T. J. Macromolecules 1997, 30, 78-86

XPS of PEM Treated Polystyrene Nitrogen 1sSulfur 2p

EOF Mobility in PEM Treated PETG

Comparison of EOF Mobility in PEM Treated PETG and PS

15 s injections 10 s injections 5 s injections PEM coated channels produce reproducible results The PEM coating can be regenerated by application of the final electrolyte layer

Avidin PEMs PEMs only Native plastic PEMs Incorporating Chemical Selectivity Reactions with fluorescein-labeled biotin

Control of Electroosmotic Flow Direction Solution Flow

Flow Imaging Advantage of this approach is that there is no distortion of the plug caused by the sample “injection” process Used to measure the effect of substrate material and microchannel geometry on sample dispersion Paul, P. H.; Garguilo, M. G.; Rakestraw, D. J. Anal. Chem. 1998, 70,

Two sides of channel have opposite charge Parallel, Opposite Flow PAH H2OH2O T-device in single plastic material Whole device first coated with PAH then PSS (negative charge) Device then treated with H2O or PAH on opposite sides of same channel Cross Sectional View

Solution Flow Flow Imaging A plug of fluorescent dye is uncaged in the microchannel Electro-osmosis moves the dye in opposite directions

Conclusions Variations in plastic surface chemistry occur due to differences in polymer composition and as a result of fabrication methods. Polyelectrolyte multilayers are effective for plastic derivatization and result in –tunable EOF mobilities –reproducible separations and assays –control of flow direction

Acknowledgements Dr. David Ross Maria I. Aquino Dr. James Hickman Heather Canavan