Fabrication of open PDMS electrospray tips integrated with microchannels using replication from a nickel master (original) (raw)
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Lab on a Chip, 2005
We describe the integration of a cyclo-olefin polymer based microchip with a sheathless capillary tip for electrospray ionization-mass spectrometry (ESI-MS). The microchip was fabricated by hot embossing and thermal bonding. Its design includes a side channel for adjusting the composition of the electrospray solution so that analytes in 100% water can be analyzed. The fused silica capillaries, used for sample introduction, and the electrospray tips for MS coupling were directly inserted into the microchannel before thermal bonding of the device. A microfabricated on-chip gold microelectrode was used to apply the electrospray voltage. Annealing the device after thermal bonding increased the pressure resistance of the microchip. The cross section of the microchannel was imaged by scanning electron microscopy to estimate the effects of the annealing step. The relationship between the applied electrospray voltages and MS signal was measured at different flow rates by coupling the device to an ion trap mass spectrometer. The performance of the microchip was evaluated by MS analysis of imipramine in ammonium acetate buffer solution by direct infusion. An alkylacrylate based monolith polymer bed for on-chip sample pretreatment and separation was polymerized in the microchannel and tested for ESI-MS applications.
Chip-based microfluidic devices coupled with electrospray ionization-mass spectrometry
ELECTROPHORESIS, 2005
Chip-based microfluidic devices coupled with electrospray ionization-mass spectrometry We present the current status of the development of microfluidic devices fabricated on different substrates for coupling with electrospray ionization-mass spectrometry (ESI-MS). Until now, much success has been gained in fabricating the ESI chips, which show better performances due to miniaturization when compared with traditional methods. Integration of multiple steps for sample preparation and ESI sample introduction, however, remains a great challenge. This review covers the main technical development of electrospray device that were published from 1997 to 2004. This article does not attempt to be exclusive. Instead, it focuses on the publications that illustrated the breath of the development and applications of microchip devices for MS-based analysis.
A new mass spectrometry electrospray tip obtained via precise mechanical micromachining
Analytical and Bioanalytical Chemistry, 2005
A new electrospray tip incorporating a beveled edge has been designed for use in plastic electrophoresis chip/electrospray mass spectrometry. Theoretical hydrodynamic analysis has been conducted to model the analytical sensitivity of the spray tip shape. A larger sample wall, that provides increased hydraulic pressure, is recommended in order to preserve the fluid stability at the tip outlet. A polymer with better hydrophobic characteristics than glass was used for the spray tip in order to restrict moisture accumulation at the spray tip outlet. Experimental results demonstrate that the analytical sensitivity of the proposed scheme is better than that obtained using the flat-head tip. Although a tapered capillary tip is commonly used in electrophoresis chip/ electrospray mass spectrometry, the proposed tip offers a similar sensitivity while being more rugged and durable than the conventional tapered capillary tip. The cost of our design is also much lower than conventional spray tips.
Fabrication and fluidic characterization of silicon micropillar array electrospray ionization chip
Sensors and Actuators B Chemical, 2008
A silicon electrospray ionization (ESI) chip for the mass spectrometric analysis is designed, fabricated, and characterized. The chip has three parts: a liquid sample introduction spot, a flow channel, and a sharp electrospray ionization tip. A regular micropillar array is micromachined inside the whole channel. The chip has no lid, which makes the sample application and chip fabrication easier. A two photomask level fabrication process utilizes nested masks of silicon dioxide and aluminum oxide. A combination of anisotropic and isotropic plasma etching steps allows formation of a truly three-dimensional electrospray ionization tip without double-sided lithography. The filling properties of the lidless micropillar channel are studied. Because of the capillary forces facilitated by the micropillar array, the sample applied onto the sample introduction spot spontaneously fills the whole flow channel including the electrospray ionization tip, without external pumping. Besides reliable self-filling, the chip offers stable electrospraying and high sensitivity chemical analysis when coupled to a mass spectrometer (MS).
Analytical Chemistry, 2011
An integrated poly(dimethylsiloxane) (PDMS) membrane-based microfluidic emitter for high performance nanoelectrospray ionization-mass spectrometry (nanoESI-MS) has been fabricated and evaluated. The ~100-μm-thick emitter was created by cutting a PDMS membrane that protrudes beyond the bulk substrate. The reduced surface area at the emitter enhances the electric field and reduces wetting of the surface by the electrospray solvent. As such, the emitter enables highly stable electrosprays at flow rates as low as 10 nL/min, and is compatible with electrospray solvents containing a large organic component (e.g., 90% methanol). This approach enables facile emitter construction, and provides excellent stability, reproducibility and sensitivity, as well as compatibility with multilayer soft lithography.
Droplet-assisted electrospray phase separation using an integrated silicon microfluidic platform
Lab on a Chip, 2021
We report a silicon microfluidic platform that enables monolithic integration of transparent micron-scale microfluidic channels, an on-chip segmentation of analyte flows into picoliter-volume droplets, and a nano-electrospray ionization emitter that enables spatial and temporal separation of oil and aqueous phases during electro-spray for subsequent mass spectrometry analysis.
A novel nib-like design for microfabricated nanospray tips
Journal of the American Society for Mass Spectrometry, 2004
We present here novel tips for nanoelectrosray ionization-mass spectrometry (ESI-MS) applications. These ionization sources have a planar geometry in the shape of a nib. Their functioning is based on a principle much akin to that of a fountain pen in that fluids are actuated by capillarity. Once a voltage is applied, an electrospray is formed at the nib tip. The nib fabrication relies on micromachining techniques using the epoxy-based negative photoresist SU-8 and a double exposure photolithographic process. Two types of nib-like sources were fabricated; they were made either conductive by metallization with a nickel layer or non-conductive but hydrophilic by covering them with a SiO 2 layer. In the latter case, the HV was applied via a Pt wire inserted into the reservoir feature of the nib. The nib-like sources were tested on an ion trap mass spectrometer using Gramicidin S samples at concentrations as low as 1 M and ionization voltages as low as 1.2 kV. We have observed a good overall stability of the spray during the tests with no marked decrease in the signal intensity even under extreme conditions. (J Am Soc Mass Spectrom 2004, 15, 409 -412)
Design and fabrication of polymer microfluidic chip for ESI-MS
BioMEMS and Nanotechnology III, 2007
In this paper, we report on the design, fabrication, and testing of a polymer micro fluidic chip for Electrospray Ionization Mass Spectrometry (ESI-MS). A disposable plastic chip is designed to be fabricated using the hot-embossing process on polystyrene (PS) and polycarbonate (PC) substrates. The chip has an open reservoir, which is connected to an open channel that runs to the tip of the chip. A high voltage circuit is required to form the electrospray at the tip using methanol/water solution with an electrode wire in the reservoir. We have tried to minimize sources of impurities entering the microchannel, and hence, the MS, by careful selection of the fabrication process and electrode and use of open channel. The hot-embossing process is modeled using ANSYS to design the tool and predict the channel and reservoir shape and deformation. The simulation results provide an insight into the hot embossing process. Several samples are fabricated and tested, and the electrospray experimental results are reported. Laser machining and electroforming processes were investigated for fabricating the hot-embossing tool, and the results are reported.