Microscale <i>p</i>H regulation by splitting water

Cheng, Li-Jing; Chang, Hsueh‐Chia

doi:10.1063/1.3657928

Cited by 76 publications

(103 citation statements)

References 25 publications

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“…phenomenon. 19 This new separation platform is capable of creating pH without supplying ampholytes in the system. To understand the heat generation in their microfluidic separation system and compare that with the traditional microchip IEF, we have simulated the IEF separation for their system.…”

Section: Effect Of Ampholyte Dissociation Constants On Maximum Temmentioning

confidence: 99%

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Effect of Joule heating on isoelectric focusing of proteins in a microchannel

2014

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Electric field-driven separation and purification techniques, such as isoelectric focusing (IEF) and isotachophoresis, generate heat in the system that can affect the performance of the separation process. In this study, a new mathematical model is presented for IEF that considers the temperature rise due to Joule heating. We used the model to study focusing phenomena and separation performance in a microchannel. A finite volume-based numerical technique is developed to study temperature-dependent IEF. Numerical simulation for narrow range IEF (6 < pH < 10) is performed in a straight microchannel for 100 ampholytes and two model proteins: staphylococcal nuclease and pancreatic ribonuclease. Separation results of the two proteins are obtained with and without considering the temperature rise due to Joule heating in the system for a nominal electric field of 100 V/cm. For the no Joule heating case, constant properties are used, while for the Joule heating case, temperature-dependent titration curves and thermo-physical properties are used. Our numerical results show that the temperature change due to Joule heating has a significant impact on the final focusing points of proteins, which can lower the separation performance considerably. In the absence of advection and any active cooling mechanism, the temperature increase is the highest at the midsection of a microchannel. We also found that the maximum temperature in the system is a strong function of the DpK value of the carrier ampholytes. Simulation results are also obtained for different values of applied electric fields in order to find the optimum working range considering the simulation time and buffer temperature. Moreover, the model is extended to study IEF in a straight microchip where pH is formed by supplying H þ and OH À , and the thermal analysis shows that the heat generation is negligible in ion supplied IEF. V C 2014 AIP Publishing LLC.

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Section: Effect Of Ampholyte Dissociation Constants On Maximum Temmentioning

confidence: 99%

“…Furthermore, the maximum temperatures along the channel are studied by varying the dissociation constants of the ampholytes. Finally, we studied the thermal characteristics in the newly introduced microchip IEF, 4,19 where pH is formed by supplying hydrogen and hydroxyl ions to show the contrasts with ampholyte based IEF.…”

Section: Introductionmentioning

confidence: 99%

Effect of Joule heating on isoelectric focusing of proteins in a microchannel

2014

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“…5(a)). 120,121 These membranes, synthesized by UV photo-polymerization, exhibit distinct hysteretic I-V polarization and cyclic voltammetry signatures due to local field-induced water-breaking reactions. At the membrane junctions, a high-voltage reverse bias depletes ions and a large field (>10 6 V/cm) develops.…”

Section: -11mentioning

confidence: 99%

Future microfluidic and nanofluidic modular platforms for nucleic acid liquid biopsy in precision medicine

et al. 2016

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Nucleic acid biomarkers have enormous potential in non-invasive diagnostics and disease management. In medical research and in the near future in the clinics, there is a great demand for accurate miRNA, mRNA, and ctDNA identification and profiling. They may lead to screening of early stage cancer that is not detectable by tissue biopsy or imaging. Moreover, because their cost is low and they are non-invasive, they can become a regular screening test during annual checkups or allow a dynamic treatment program that adjusts its drug and dosage frequently. We briefly review a few existing viral and endogenous RNA assays that have been approved by the Federal Drug Administration. These tests are based on the main nucleic acid detection technologies, namely, quantitative reverse transcription polymerase chain reaction (PCR), microarrays, and next-generation sequencing. Several of the challenges that these three technologies still face regarding the quantitative measurement of a panel of nucleic acids are outlined. Finally, we review a cluster of microfluidic technologies from our group with potential for point-of-care nucleic acid quantification without nucleic acid amplification, designed to overcome specific limitations of current technologies. We suggest that integration of these technologies in a modular design can offer a low-cost, robust, and yet sensitive/selective platform for a variety of precision medicine applications.

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“…16 Also, BMs have also been utilized to generate H þ and OH À ions in lab-on-a-chip applications. 2,17 However, the EFE water dissociation effect diminishes the diode property of BMs when operated outside the 61 V window, which is unwanted in, for instance, chemical circuits and addressing matrices for delivery of complex gradients of chemical species. The effect can be suppressed by incorporating a neutral electrolyte inside the BM, 10,18 for instance, poly(ethylene glycol) (PEG).…”

mentioning

confidence: 99%

“…17,18 As no additional neutral layer at the BM interface is needed, ion diodes that operate outside the usual EFE water dissociation window of 61 V can be constructed using less active layers, fewer processing steps and with relaxed alignment requirement as compared to polyammonium-based devices. This enables the fabrication of ion rectification devices with an active interface as low as 10 lm.…”

mentioning

confidence: 99%

Polyphosphonium-based bipolar membranes for rectification of ionic currents

Gabrielsson

Berggren

2013

Biomicrofluidics

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Bipolar membranes (BMs) have interesting applications within the field of bioelectronics, as they may be used to create non-linear ionic components (e.g., ion diodes and transistors), thereby extending the functionality of, otherwise linear, electrophoretic drug delivery devices. However, BM based diodes suffer from a number of limitations, such as narrow voltage operation range and/or high hysteresis. In this work, we circumvent these problems by using a novel polyphosphonium-based BM, which is shown to exhibit improved diode characteristics. We believe that this new type of BM diode will be useful for creating complex addressable ionic circuits for delivery of charged biomolecules. Combined electronic and ionic conduction makes organic electronic materials well suited for bioelectronics applications as a technological mean of translating electronic addressing signals into delivery of chemicals and ions. 1 For complex regulation of functions in cells and tissues, a chemical circuit technology is necessary in order to generate complex and dynamic signal gradients with high spatiotemporal resolution. One approach to achieve a chemical circuit technology is to use bipolar membranes (BMs), which can be used to create the ionic equivalents of diodes 2-5 and transistors. 6-8 A BM consists of a stack of a cation-and an anionselective membrane, and functions similar to the semiconductor PN-junction, i.e., it offers ionic current rectification 9,10 (Figure 1(a)). The high fixed charge concentration in a BM configuration make them more suited in bioelectronic applications as compared to other non-linear ionic devices, such as diodes constructed from surface charged nanopores 11 or nanochannels, 12 as the latter devices typically suffers from reduced performance at elevated electrolyte concentration (i.e., at physiological conditions) due to reduced Debye screening length. 13 However, a unique property of most BMs, as compared to the electronic PN-junction and other ionic diodes, is the electric field enhanced (EFE) water dissociation effect. 10,14 This occurs above a threshold reverse bias voltage, typically around À1 V, as the high electric field across the ion-depleted BM interface accelerates the forward reaction rate of the dissociation of water into H þ and OH À ions. As these ions migrate out from the BM, there will be an increase in the reverse bias current. The EFE water dissociation is a very interesting effect and is commonly used in industrial electrodialysis applications, 15 where highly efficient water dissociating BMs are being researched. 16 Also, BMs have also been utilized to generate H þ and OH À ions in lab-on-a-chip applications. 2,17 However, the EFE water dissociation effect diminishes the diode property of BMs when operated outside the 61 V window, which is unwanted in, for instance, chemical circuits and addressing matrices for delivery of complex gradients of chemical species. The effect can be suppressed by incorporating a neutral electrolyte inside the BM, 10,18 for instance, poly(ethylene glyc...

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Microscale pH regulation by splitting water

Cited by 76 publications

References 25 publications

Effect of Joule heating on isoelectric focusing of proteins in a microchannel

Effect of Joule heating on isoelectric focusing of proteins in a microchannel

Future microfluidic and nanofluidic modular platforms for nucleic acid liquid biopsy in precision medicine

Polyphosphonium-based bipolar membranes for rectification of ionic currents

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