ABSTRACT
By use of synchrotron X-ray fluorescence and Rutherford backscattering spectrometry, we show the SU-8 soft lithographic process contaminates PDMS. Residues of the antimony containing photoinitiator are transferred from the master mold to the surface of PDMS, uncontrollably intensifying the surface potential, leading to electroosmotic flow variability in PDMS microfluidic devices.
Subject(s)
Dimethylpolysiloxanes/chemistry , Microfluidic Analytical Techniques/instrumentation , Antimony/chemistry , Surface PropertiesABSTRACT
We discuss the use of aqueous NaOH as a facile surface treatment method to control the electroosmotic flow in PDMS microchannels. Flushing of PDMS/PDMS and glass/PDMS microchannels with 1 M NaOH for 24 h leads to a doubling of the electroosmotic flow. This high flow rate is comparable to the flow rates achieved by treating PDMS microchannels with O2 plasma. Contact angle measurements and ATR-FTIR analysis show that the surface chemistry of the NaOH treated PDMS differs from O2 plasma treated PDMS. An important advantage of the NaOH treated surfaces is the enhanced stability, irrespective of whether the devices are stored in air or water.
