Surfaces of Alcohol−Water Mixtures Studied by Sum-Frequency Generation Vibrational Spectroscopy

Sung, Jaeho; Park, Kyung-Su; Kim, Doseok

doi:10.1021/jp051959h

Cited by 100 publications

(184 citation statements)

References 63 publications

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“…To manipulate the interfacial tension, ethanol was mixed in varying ratios with water. 29 The ethanol/water mixture was then used to form virtual walls in the PDMS device. As expected, the critical pressure ⌬p c was reduced as the content of ethanol was increased or surface tension decreased ͓Fig.…”

Section: Influence Of Surface Tension On the Adhesion Of Virtual Wmentioning

confidence: 99%

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications

Lai

Allbritton

2011

Biomicrofluidics

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A simple method for micromanipulation of liquids and/or small groups of cells is presented in this study. Microfabricated sieving structures composed of PDMS ͑polydimethylsiloxane͒ were used to segregate aqueous solutions. This microfluidic valving scheme was an application of Cassie-Baxter wetting and was termed "virtual walls" as a nonsolid barrier exists at an air/water interface. The manipulation of the virtual-air-wall valve was accomplished by controlling the strength of surfacetension and hydrostatic-pressure forces. Virtual walls with a range of feature sizes were designed and characterized by monitoring air and water displacement in response to hydrostatic pressure. Thresholds for the virtual-air-wall valves to be turned on or off were quantified. The walls could also be formed or dissipated by the focused microbeam of a pulsed laser. As an illustration of the virtual wall utility, a series of microfluidic applications were demonstrated. First, the capability of virtual walls to temporarily segregate liquids was integrated into a device utilized to establish a chemical gradient. In a second application, the arraying of nonadherent cells within individual aqueous cavities created by the virtual walls was demonstrated. Individual cells were also released from the cavities on demand using a focused microbeam. The virtual walls were simple and easy-to-fabricate without the requirement for surface treatment or precision alignment, and should find usage in bioanalytical applications.

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Section: Influence Of Surface Tension On the Adhesion Of Virtual Wmentioning

confidence: 99%

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications

Lai

Allbritton

2011

Biomicrofluidics

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“…[10][11][12][13][14][15][16][17] As we have reported recently, some assignments for the C-H stretching vibrational spectra are ambiguous or incorrect even for some simple molecules such as methanol and ethanol, [1,2] and the incorrect spectral assignments have been applied to interpret many important dynamical processes. [4,[17][18][19][20] Compared with methanol and ethanol, the vibrational spectrum of 2-propanol is more complex because of the increased C-H groups. Although the extensive studies have been conducted to investigate the vibrational spectra of 2-propanol in the C-H stretching region, its assignment is still controversial at the present time.…”

Section: Introductionmentioning

confidence: 99%

Overlapping spectral features and new assignment of 2‐propanol in the C–H stretching region

Wang

et al. 2014

J Raman Spectroscopy

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The vibrational spectra of gaseous and liquid 2-propanol in the C-H stretching region of 2800~3100 cm À1 were investigated by polarized photoacoustic Raman spectroscopy and conventional Raman spectroscopy, respectively. Using two deuterated samples, that is, CH 3 CDOHCH 3 and CD 3 CHOHCD 3 , the overlapping spectral features between the CH and CH 3 groups were identified. With the aid of depolarization ratio measurements and density functional theory calculations, a new spectral assignment was presented. In the gas phase, the band at 2884 cm À1 was assigned to the overlapping of one CH 3 Fermi resonance mode and a CH stretching of gauche conformer. The bands at 2917 and 2933 cm À1 were assigned to another two CH 3 Fermi resonance modes, but the latter includes weak contribution from CH stretching of trans conformer. The bands at 2950 and 2983 cm À1 were assigned to CH 3 symmetric and antisymmetric stretching, respectively. The spectral features of liquid 2-propanol are similar to those in the gas phase except for the blue shift of CH and the red shift of CH 3 band positions, which can be attributed to the intermolecular interaction in the liquid state. The new assignments not only clarify the confusions in previous studies from different spectral methods but also provide the reliable groundwork on spectral application of 2-propanol in the futures.

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“…The dots represent the mean value of the surface tension, and the error bars show the range of the data. The results of previous reports [20][21][22] are also presented in Figure 7. There is good agreement between our results and that of previous reports.…”

Section: Surface Tension Measurementmentioning

confidence: 66%

Digital image processing of sectorial oscillations for acoustically levitated drops and surface tension measurement

Shen

Xie

Wei

2010

Sci. China Phys. Mech. Astron.

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A type of non-axisymmetric oscillations of acoustically levitated drops is excited by modulating the ultrasound field at proper frequencies. These oscillations are recorded by a high speed camera and analyzed with a digital image processing method. They are demonstrated to be the third mode sectorial oscillations, and their frequencies are found to decrease with the increase of equatorial radius of the drops, which can be described by a modified Rayleigh equation. These oscillations decay exponentially after the cessation of ultrasound field modulation. The decaying rates agree reasonably with Lamb's prediction. The rotating rate of the drops accompanying the shape oscillations is found to be less than 1.5 rounds per second. The surface tension of aqueous ethanol has been measured according to the modified Rayleigh equation. The results agree well with previous reports, which demonstrates the possible application of this kind of sectorial oscillations in noncontact measurement of liquid surface tension. acoustic levitation, drop oscillation, image processing, surface tension

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Surfaces of Alcohol−Water Mixtures Studied by Sum-Frequency Generation Vibrational Spectroscopy

Cited by 100 publications

References 63 publications

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications

Use of a virtual wall valve in polydimethylsiloxane microfluidic devices for bioanalytical applications

Overlapping spectral features and new assignment of 2‐propanol in the C–H stretching region

Digital image processing of sectorial oscillations for acoustically levitated drops and surface tension measurement

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