Colloid Coalescence with Focused X Rays

Weon, Byung Mook; Kim, J. T.; Je, Jung Ho; Yi, J. M.; Wang, S.; Lee, W.-K.

doi:10.1103/physrevlett.107.018301

Cited by 11 publications

(10 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1c, with a high spatial resolution (~50 nm per pixel) without using any contrast agents. The interference bright and dark fringes at each interface, originating from the Zernike phase contrast3738, allowed us to clearly identify each interface3940. We for the first time found that wetting ridges in large drops ( r ≈1 mm) have bent cusps (Fig.…”

Section: Resultsmentioning

confidence: 78%

“…A Fresnel zone plate was used as an objective lens. For phase-contrast enhancement, we used a Au Zernike phase ring, optimized for 9 keV, which is very useful to imaging soft matters such as organic3940 or biological samples3738 without any contrast agents. Image taking was started within 1–2 min after contact line pinning, under controlled temperature (22.5 °C) and humidity (19.5%).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Visualization of asymmetric wetting ridges on soft solids with X-ray microscopy

et al. 2014

View full text Add to dashboard Cite

One of the most questionable issues in wetting is the force balance that includes the vertical component of liquid surface tension. On soft solids, the vertical component leads to a microscopic protrusion of the contact line, that is, a ‘wetting ridge’. The wetting principle determining the tip geometry of the ridge is at the heart of the issues over the past half century. Here we reveal a universal wetting principle from the ridge tips directly visualized with high spatio-temporal resolution of X-ray microscopy. We find that the cusp of the ridge is bent with an asymmetric tip, whose geometry is invariant during ridge growth or by surface softness. This singular asymmetry is deduced by linking the macroscopic and microscopic contact angles to Young and Neuman laws, respectively. Our finding shows that this dual-scale approach would be contributable to a general framework in elastowetting, and give hints to issues in cell-substrate interaction and elasto-capillary problems.

show abstract

Section: Resultsmentioning

confidence: 78%

Section: Methodsmentioning

confidence: 99%

Visualization of asymmetric wetting ridges on soft solids with X-ray microscopy

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Theory.-The coalescence motions are, after initial neck growth [9,10,[26][27][28], controlled by the slow release of surface energy Ás (s is the surface area) [27,28]. For an ideal case of two spheres (with radii r L and r S ) that form a new sphere (with r M ), the mass conservation dictates r M ¼ ðr L 3 þ r S 3 Þ 1=3 [22,28].…”

mentioning

confidence: 99%

“…The coalescence preference would be valid for both sessile and free spheres because the surface energy release holds regardless of the existence of a ground interface. The universal nature of the coalescence preference requires further studies in terms of fluid wettability [17] or fluid viscosity [26].…”

mentioning

confidence: 99%

Coalescence Preference Depends on Size Inequality

Weon

2012

Phys. Rev. Lett.

View full text Add to dashboard Cite

During bubble or droplet coalescence, there is a puzzling tendency for the coalesced bubble or droplet to be preferentially placed closer to the larger of its two parents. We confirm that this preference is a function of parent size ratio by directly visualizing coalescing air bubbles on an oil-water interface and coalescing water droplets immersed in oil. We find that the final position of the coalesced sphere is controlled by surface energy release and is related to the parent size ratio by a power-law relationship.

show abstract

“…This X-ray-induced effect can be fully recovered by a sufficient pause in the irradiation. High-brilliance X-rays can modify material properties, including surface tension and viscosity [28]. A very short exposure on the μs timescale would be useful to prevent any X-ray-induced changes [29,30].…”

Section: Introductionmentioning

confidence: 99%

X-ray-induced water vaporization

Weon

Lee

et al. 2011

Phys. Rev. E

Self Cite

View full text Add to dashboard Cite

We present quantitative evidence for X-ray-induced water vaporization: water is vaporized at a rate of 5.5 pL/s with the 1-Å-wavelength X-ray irradiation of ~0.1 photons per Å 2 ; moreover, water vapor is reversibly condensed during pauses in irradiation. This result fundamentally suggests that photoionization induces vaporization. This phenomenon is attributed to surface tension reduction by ionization and would be universally important in radiological and electrohydrodynamic situations.PACS numbers: 68.03. Fg, 68.03.Cd, 78.70.-g * E-mail: bmweon@hotmail.com, † jhje@postech.ac.krBrief Report -Physical Review E -2 -X-ray photonics is undergoing a revolution in imaging capabilities with the use of ultrabright X-ray sources. X-ray imaging at the nano-and microscale is of great interest for applications in physical and life sciences, including X-ray physics, materials science, biological imaging, environmental analysis, archaeology, paleontology, and heritage restoration [1], because it facilitates the nondestructive, direct visualization of internal structures or elements.Meanwhile, radiation damage from the energy deposited into the sample by the X-ray photons used for imaging is inevitable [2,3]. In particular, radiation-induced ionization ultimately disintegrates the sample by charge accumulation beyond a limit and is otherwise known as Coulomb explosion [2,3] and fission [4,5]. The conventional damage barrier for Coulomb explosion is known to be about 200 photons per Å 2 for X-rays with a wavelength of 1 Å [2,3].Radiation damage can be mitigated by cryofixation or by ultrabright, ultrashort X-ray pulses [2].However, radiation damage to living tissues by radiation ionization is not yet fully understood[6], although it is a limiting factor in achieving high-resolution data [2].In previous works, we demonstrated that high-brilliance X-ray photons affect the surface tension of water by inducing ionization, using hard X-ray imaging at the 7B2 beamline (dose rate ~1 kGy s -1 ) of the Pohang Light Source [7][8][9]. A charge density over ~10 -4 charges per Å 2 was required for a significant reduction (> 30%) in the surface tension [9]. This condition corresponds to X-ray irradiation of ~0.1 photons per Å 2 , following a simulation using the ionization rate of ~1 charge per Å 2 by 2000 photons per Å 2 with X-rays of 1 Å wavelength [2].We put forward a possibility of water vaporization by surface tension reduction [7,8] based on a monotonic relationship of the surface tension to the vaporization enthalpy [10,11], but quantitative evidence was lacking.To corroborate the possibility, we conducted an elaborate experiment in a different synchrotron source while applying high-speed X-ray imaging [12,13]. Using a hydrophilic capillary tube containing a small amount of water, we first made a confined water lens with concave menisci, where the left region was closed and the right one was open in air [ Fig. 1]. The changes of the water menisci were simultaneously imaged using a high-speed camera, synchronized and gated t...

show abstract

Colloid Coalescence with Focused X Rays

Cited by 11 publications

References 32 publications

Visualization of asymmetric wetting ridges on soft solids with X-ray microscopy

Visualization of asymmetric wetting ridges on soft solids with X-ray microscopy

Coalescence Preference Depends on Size Inequality

X-ray-induced water vaporization

Contact Info

Product

Resources

About