Hybrid integrated PDMS microfluidics with a silica capillary (original) (raw)
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TRANSDUCERS 2009 - 2009 International Solid-State Sensors, Actuators and Microsystems Conference, 2009
We present an effective hybrid integration of PDMS microfluidic devices and fused silica capillaries. These hybrid microfluidic Integrated PDMS and Silica Capillary (iPSC) modules exhibit a novel architecture and method for leakage free CE sample injection requiring only a single high voltage source. Use of the iPSC devices is based on a modular approach which allows the capillary to be reused over 1,000 times whilst replacing the fluidics below it for different experiments. Integrating fused silica capillaries with PDMS microfluidics allows the direct application of a wide variety of well established conventional CE protocols for complex analyte separations and ESI-MS coupling, allowing users to focus on the sample analysis rather than the development of new separation protocols. The iPSC fabrication method is simple (3 steps) and quick (7 min).
Microfluidic device for capillary electrochromatography-mass spectrometry
ELECTROPHORESIS, 2003
A novel microfabricated device that integrates a monolithic polymeric separation channel, an injector, and an interface for electrospray ionization-mass spectrometry detection (ESI-MS) was devised. Microfluidic propulsion was accomplished using electrically driven fluid flows. The methacrylate-based monolithic separation medium was prepared by photopolymerization and had a positively derivatized surface to ensure electroosmotic flow (EOF) generation for separation of analytes in a capillary electrochromatography (CEC) format. The injector operation was optimized to perform under conditions of nonuniform EOF within the microfluidic channels. The ESI interface allowed hours of stable operation at the flow rates generated by the monolithic column. The dimensions of one processing line were sufficiently small to enable the integration of 4-8 channel multiplexed structures on a single substrate. Standard protein digests were utilized to evaluate the performance of this microfluidic chip. Low-or sub-fmol amounts were injected and detected with this arrangement.
Journal of Chromatography A, 2013
Two-dimensional electrophoretic separations are one of the most promising tools for the continuously growing needs of different bioanalytical fields such as proteomics and metabolomics. In this work we present the design and the implementation of a two-dimensional electrophoretic separation coupled to mass spectrometry. We started our work studying the sample transfer characteristics of different microfluidic interfaces compatible with capillary coupling for two-dimensional electrophoretic separations. These junctions are aimed at method decoupling and sample transfer in a modular two-dimensional electrophoretic separation system. In order to perform the characterization of the interfaces, we carried out capillary electrophoresis experiments and numerical simulations using three cationic compounds under different flow conditions. The comparison of the experimental and simulation results enables us to clearly define the desirable characteristics of interfaces in order to achieve method orthogonality with lossless sample transfer in a two-dimensional separation system. Finally, we present a glass microfluidic chip as interface for the implementation of a novel hybrid modular system for performing two-dimensional electrophoretic separations involving isotachophoresis and capillary electrophoresis. In this setup we include mass spectrometric and contactless capacitively coupled conductivity detection to monitor the separation process. We demonstrate the ability of the setup to be used as a flexible analysis tool by performing preconcentration, separation, detection and identification of four different human angiotensin peptides.
Analytical Chemistry, 2007
A robust, reproducible, and single-step interface design between low flow rate separation techniques, such as sheathless capillary electrophoresis (CE) and nanoliquid chromatography (nLC), and mass spectrometry (MS) using electrospray ionization (ESI), is introduced. In this design, the electrical connection to the capillary outlet was achieved through a porous tip at the capillary outlet. The porous section was created by removing 1-1.5 in. of the polyimide coating of the capillary and etching this section by 49% solution of HF until it is porous. The electrical connection to the capillary outlet is achieved simply by inserting the capillary outlet containing the porous tip into the existing ESI needle (metal sheath) and filling the needle with the background electrolyte. Redox reactions of water at the ESI needle and transport of these small ions through the porous tip into the capillary provides the electrical connection for the ESI and for the CE outlet electrode. The etching process reduces the wall thickness of the etched section, including the tip of the capillary, to 5-10 µm, which for a 20-30 µm i.d. capillary results in stable electrospray at ∼1.5 kV. The design is suitable for interfacing a wide range of capillary sizes with a wide range of flow rates to MS via ESI, but it is especially useful for interfacing narrow (<30 µm i.d.) capillaries and low flow rates (<100 nL/min). The advantages of the porous tip design include the following: (1) its fabrication is reproducible, can be automated, and does not require any mechanical tools. (2) The etching process reduces the tip outer diameter and makes the capillary porous in one step.
A polymeric microfluidic chip for CE/MS determination of small molecules
2001
A polymeric microfluidic chip made of Zeonor 1020 was fabricated using conventional embossing techniques to perform capillary electrophoresis for selected ion monitoring and selected reaction monitoring mass spectrometric detection of small molecules. A silicon master was microfabricated using photolithographic and dry etching processes. The microfluidic channel was embossed in the plastic from a silicon master. The embossed chip was thermally bonded with a Zeonor 1020 cover to form an enclosed channel. This channel (60-µm width, 20-µm depth, 2.0-and 3.5-cm length) provided capillary electrophoresis (CE) separation of polar small molecules without surface treatment of the polymer. A microsprayer coupled via a microliquid junction provided direct electrospray mass spectrometric detection of CE-separated components. An electric field of 0.5-2 kV/cm applied between the microsprayer and a separation buffer reservoir produced a separation of carnitine, acylcarnitine, and butylcarnitine with separation efficiencies ranging from 1650 to 18 000 plates. Injection quantities of 0.2 nmol of these compounds produced a separation of the targeted polar small molecules without surface treatment of the polymer-abundant ion current signals and baseline separation of these compounds in less than 10 s. These results suggest the feasibility of polymeric chip-based devices for ion spray CE/MS applications.
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.
Analytical Chemistry, 2000
A simple procedure was developed for preparing a carboncoated fused-silica capillary for use in sheathless capillary electrophoresis/electrospray mass spectrometry (CE/ESI-MS). The tapered capillary tip was smeared with a marker pen before coating with carbon using a soft pencil. The layer from the ink of the marker pen was critical to the preparation of the carbon-coated capillary. The fabrication of a carbon-coated fused-silica capillary tip requires less than 1 min. The stability of this carbon-coated fused-silica capillary is examined, and its utility in on-line sheathless CE/ESI-MS is demonstrated with the separation of berberine, coptisine, and palmatine chlorides. Although the carbon-coated fused-silica capillary tip is not as rugged as a gold-coated capillary, it is durable enough for sheathless CE/ESI-MS applications. Moreover, it is easy to refurbish the column once the performance of the tip is degraded. Capillary electrophoresis (CE) is a powerful separation technique which has rapidly developed and matured since its introduction. 1,2 Because of its salient universality, relatively high sensitivity, and structural elucidation capability, mass spectrometry is expected to become one of the most powerful and popular CE detectors. 3,4 Currently, electrospray ionization (ESI) serves as the most common ionization method for CE/MS applications. 5-7 One major requirement for using ESI-MS as an on-line detector in CE separations is the provision of electrical contact at the capillary outlet. The most widely used interface for commercial CE/ESI-MS instrumentation is the sheath-flow interface. 8 At the sheathflow interface, a coaxial sheath liquid was introduced which served to establish the electrical contact for CE. This method offers several advantages, including reliability, simple fabrication, and
Analytical Chemistry, 2003
An electrokinetic injection technique is described which uses a nuclear track-etched nanocapillary array to inject sample plugs from one layer of a microfluidic device into another vertically separated layer for electrophoretic separations. Gated injection protocols for analyte separations, reported here, establish nanocapillary array interconnects as a route to multilevel microfluidic analytical designs. The hybrid nanofluidic/microfluidic gated injection protocol allows sample preparation and separation to be implemented in separate horizontal planes, thereby achieving multilayer integration. Repeated injections and separations of FITC-labeled arginine and tryptophan, using 200-nm pore-diameter capillary array injectors in place of traditional cross injectors are used to demonstrate gated injection with a bias configuration that uses relay switching of a single high-voltage source. Injection times as rapid as 0.3 s along with separation reproducibilities as low as 1% for FITC-labeled arginine exemplify the capability for fast, serial separations and analyses. Impedance analysis of the micro-/nanofluidic network is used to gain further insight into the mechanism by which this actively controlled nanofluidic-interconnect injection method works. Gated sample introduction via a nanocapillary array interconnect allows the injection and separation protocols to be optimized independently, thus realizing the versatility needed for real-world implementation of rapid, serial microchip analyses.
High performance microfluidic capillary electrophoresis devices
Biomedical Microdevices, 2007
This paper presents a novel microfluidic capillary electrophoresis (CE) device featuring a double-T-form injection system and an expansion chamber located at the inlet of the separation channel. This study addresses the principal material transport mechanisms depending on parameters such as the expansion ratio, the expansion length, the fluid flow. Its design utilizes a double-L injection technique and combines the expansion chamber to minimize the sample leakage effect and to deliver a highquality sample plug into the separation channel so that the detection performance of the device is enhanced. Experimental and numerical testing of the proposed microfluidic device that integrates an expansion chamber located at the inlet of the separation channel confirms its ability to increase the separation efficiency by improving the sample plug shape and orientation. The novel microfluidic capillary electrophoresis device presented in this paper has demonstrated a sound potential for future use in high-quality, high-throughput chemical analysis applications and throughout the micro-total-analysis systems field.