Integration of multiple components in polystyrene-based microfluidic devices part I: fabrication and characterization

Abstract

In Part I of a two-part series, we describe a simple, and inexpensive approach to fabricate polystyrene devices that is based upon melting polystyrene (from either a Petri dish or powder form) against PDMS molds or around electrode materials. The ability to incorporate microchannels in polystyrene and integrate the resulting device with standard laboratory equipment such as an optical plate reader for analyte readout and micropipettors for fluid propulsion is first described. A simple approach for sample and reagent delivery to the device channels using a standard, multi-channel micropipette and a PDMS-based injection block is detailed. Integration of the microfluidic device with these off-chip functions (sample delivery and readout) enables high throughput screens and analyses. An approach to fabricate polystyrene-based devices with embedded electrodes is also demonstrated, thereby enabling the integration of microchip electrophoresis with electrochemical detection through the use of a palladium electrode (for a decoupler) and carbon-fiber bundle (for detection). The device was sealed against a PDMS-based microchannel and used for the electrophoretic separation and amperometric detection of dopamine, epinephrine, catechol, and 3,4-dihydroxyphenylacetic acid. Finally, these devices were compared against PDMS-based microchips in terms of their optical transparency and absorption of an anti-platelet drug, clopidogrel. Part I of this series lays the foundation for Part II, where these devices were utilized for various on-chip cellular analysis.

Integrated hybrid polystyrene–polydimethylsiloxane device for monitoring cellular release with microchip electrophoresis and electrochemical detection

“…19,21,22,31 The work described here utilizes PS for its ability to embed electrodes for analysis and fluidic tubing to provide a low dead-volume connection to direct flow from sample (or immobilized cells) to the analysis device. 16,18 Importantly, the ability to embed the tubing allows us to integrate the chip with off-chip, well-established culture methods such as conventional petri dishes in a manner that does not significantly degrade the temporal resolution (discussed in more detail below). The PS embedded Pd decoupler has a large surface area and is capable of absorbing the increased hydrogen production at the decoupler due to increased ionic strength and current.…”

“…A simple and reproducible fabrication approach has been described that incorporates multiple electrode materials and allow electrode polishing to generate a fresh electrode surface when desired. 16,17 It has been shown that the resulting embedded Pd decouplers have improved performance and are capable of dissipating the hydrogen production from the electrolysis of water associated with highly conductive biological buffers. The use of higher field strengths is possible with the embedded Pd decouplers (as opposed to the thin-layer Pd decouplers) due to the increased surface area of the Pd, which allows for more H 2 dissipation.…”

Microfluidic device with tunable post arrays and integrated electrodes for studying cellular release

“…Following the assembly of the mold and electrodes, polystyrene powder (250 µm particle size) was poured into the electrode mold and melted at 270°C (on a hot plate) for approximately 4 hours. 21 After the polystyrene powder melted, it was left to cool slowly (~20 minutes). The aluminum mold was removed and the polystyrene was shaped by wet polishing, as previously reported.…”

“…The aluminum mold was removed and the polystyrene was shaped by wet polishing, as previously reported. 21 …”

Cyclic Block Copolymer Microchannel Fabrication and Sealing for Microfluidics Applications

“…Compared with PDMS, thermoplastic is a rigid polymer material that can be shaped or reshaped upon heating above the glass transition temperature (T g ). Myriad thermoplastic materials, such as polycarbonate (PC) [14][15][16], polymethyl methacrylate (PMMA) [17][18][19], cyclic olefin polymers (COPs) [20][21][22][23], polystyrene (PS) [24][25][26], and polyethylene terephthalate (PET) [27,28] have been employed in microfluidics. Among them, COPs have high optical transmissivity, satisfactory solvent and acid and base resistivity, and glass-like properties.…”