Derivatization of Plastic Microfluidic Devices with Polyelectrolyte Multilayers

1. 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

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

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

4. press Al block plastic template Al block press Room TemperatureImprinting PDMS Lid Plastic Substrate Xu, J.; Locascio, L. E.; Lee, C. S. Anal. Chem.2000,72, 1930-1933.

5. EOF Comparison *Huang, X.; Gordon, M.; Zare, R.N. Anal. Chem. 1988, 60, 1837. §Locascio, L., Perso, C., Lee, C. J. Chrom., A 1999, 857, 275-284.

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

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

8. •HCl CH2NH2 CH2CH n SO3-Na+ Polyelectrolytes Polystyrene sulfonate Poly(allylamine hydrochloride) n • 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. Macromolecules1997,30, 78-86

9. XPS of PEM Treated Polystyrene Nitrogen 1s Sulfur 2p

10. EOF Mobility in PEM Treated PETG

11. Comparison of EOF Mobility in PEM Treated PETG and PS

12. 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

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

14. - + Solution Flow + + + + + + + + - + + + + + + + + + + + Solution Flow + + + + + + + + + + + + + + + + + + Control of Electroosmotic Flow Direction + + + + + + + +

15. Flow Imaging Used to measure the effect of substrate material and microchannel geometry on sample dispersion Advantage of this approach is that there is no distortion of the plug caused by the sample “injection” process Paul, P. H.; Garguilo, M. G.; Rakestraw, D. J. Anal. Chem.1998,70, 2459-2467

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

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

18. 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

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