The zeta potential of cyclo-olefin polymer microchannels and its effects on insulative (electrodeless) dielectrophoresis particle trapping devices

Abstract

While cyclo-olefin polymer microchannels have the potential to improve both the optical detection sensitivity and the chemical resistance of polymer microanalytical systems, their surface properties are to date not thoroughly characterized. These surface properties dictate, among other things, electrokinetic effects when electric fields are present. Here, we report the measurement of the zeta potential of cyclo-olefin polymers (injection-molded and hot-embossed Zeonor 1060R and 1020R) microchannels as a function of pH, counter-ion concentration, storage conditions, and chemical treatment in aqueous solutions both with and without EOF-suppressing additives. In contrast with previous reports, significant surface charge is measured, consistent with titration of charged sites with pK(a) = 4.8. Storage in air, acetonitrile, or aqueous solutions has relatively minor effects. While the source of the surface charge is unclear, chemical functionalization has shown that carboxylic acid groups are not present at the surface, consistent with the chemical structure of Zeonor. EOF-suppressing additives (hydroxypropylmethylcellulose) and conditioning in perchloric acid allow the surface charge to be suppressed. We demonstrate dielectrophoretic particle trapping devices in Zeonor 1060R substrates that show reduced trapping voltage thresholds as compared to previous implementations in glass.

A method for simultaneously determining the zeta potentials of the channel surface and the tracer particles using microparticle image velocimetry technique

“…In the improved method a general least-square analysis is used to account for measurement uncertainties. Mela et al [12] used the streaming potential method to measure the zeta potential for characterizing the cyclo-olefin polymer microchannels. Sze et al [13] used the current monitoring method [14] to determine the zeta potentials of channel surfaces by using the Smoluchowski equation together with the measured slope of current-time relationship in EOFs.…”

Bacteria concentration using a membrane type insulator‐based dielectrophoresis in a plastic chip

“…The iDEP chip has been employed to selectively trap and concentrate both live and dead E. coli and separate different species of live bacterial cells from water School of Nano-Biotechnology and Chemical Engineering, UNIST, Ulsan, Republic of Korea using a direct current electric field [7,12,13,19]. Mela et al, reported reduced trapping voltage thresholds for the iDEP chips fabricated with cyclo-olefin polymer as compared with the previously reported glass-based iDEP chips [22].…”

“…In iDEP chips, the DEP trap is formed by geometrical constrictions in insulating substrates (e.g. quartz [6,7,12,13,18], glass beads [20,24], cyclo-olefin polymer [22], PMMA [21], and polycarbonate (PC) [23]) instead of metallic microelectrodes. A Nonuniform electric field is generated near the non-uniform structures made of insulating materials when an electric field is applied to remotely located electrodes.…”

Electroactive intercalators for DNA analysis on microchip electrophoresis

“…Several polymers such as poly(methylmethacrylate) (PMMA) [4], PDMS [5], polycarbonate (PC) [6], polyester [7], and poly(ethylenterephthalate) (PET) [8] have been employed. Recently, cyclic olefin polymers and copolymers such as Zeonor [9] or thermoplastic olefin polymer of amorphous structure (Topas) [10] have also received attention due to their high chemical resistance, good machinability, and optical transparency.…”