Droplets on Inclined Plates: Local and Global Hysteresis of Pinned Capillary Surfaces

Local contact line pinning prevents droplets from rearranging to minimal global energy, and models for droplets without pinning cannot predict their shape. We show that experiments are much better described by a theory, developed herein, that does account for the constrained contact line motion, using as example droplets on tilted plates. We map out their shapes in suitable phase spaces. For 2D droplets, the critical point of maximum tilt depends on the hysteresis range and Bond number. In 3D, it also depends on the initial width, highlighting the importance of the deposition history.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. Let

Plaque burden is associated with minimal intimal coverage following drug-eluting stent implantation in an adult familial hypercholesterolemia swine model

Abstract Safety and efficacy of coronary drug-eluting stents (DES) are often preclinically tested using healthy or minimally diseased swine. These generally show significant fibrotic neointima at follow-up, while in patients, incomplete healing is often observed. The aim of this study was to investigate neointima responses to DES in swine with significant coronary atherosclerosis. Adult familial hypercholesterolemic swine (n = 6) received a high fat diet to develop atherosclerosis. Serial OCT was performed before, directly after, and 28 days after DES implantation (n = 14 stents). Lumen, stent and plaque area, uncovered struts, neointima thickness and neointima type were analyzed for each frame and averaged per stent. Histology was performed to show differences in coronary atherosclerosis. A range of plaque size and severity was found, from healthy segments to lipid-rich plaques. Accordingly, neointima responses ranged from uncovered struts, to minimal neointima, to fibrotic neointima. Lower plaque burden resulted in a fibrotic neointima at follow-up, reminiscent of minimally diseased swine coronary models. In contrast, higher plaque burden resulted in minimal neointima and more uncovered struts at follow-up, similarly to patients’ responses. The presence of lipid-rich plaques resulted in more uncovered struts, which underscores the importance of advanced disease when performing safety and efficacy testing of DES

Flows around Confined Bubbles and Their Importance in Triggering Pinch-Off

We describe the breakup of a confined gas thread in a cross-flowing stream of liquid at capillary numbers Ca<10-2. The breakup is initiated, not by a Plateau-Rayleigh instability, but by liquid that flows from the tip of the thread to the neck where pinch-off occurs. This flow, faster than previously estimated, is driven by different curvatures at the tip and neck and runs through large gaps between thread and channel walls. Understanding how these curvatures evolve during bubble formation leads to accurate predictions of the moment of pinch-off.DelftChemTechApplied Science

Robust surface-subsurface modification of PDMS through atmospheric pressure atomic layer deposition

Polydimethylsiloxane (PDMS) has been widely employed as a material for microreactors and lab-on-a-chip technologies. However, in its applications, PDMS suffers from two major problems: its weak resistance against common organic solvents and its chemically non-functional surface. To overcome both issues, atmospheric pressure atomic layer deposition (AP-ALD) can be used to deposit an inorganic nano-layer (TiOx) on PDMS that in turn can be further functionalized. The inorganic nano-layer is previously communicated to durably increase the organic solvent resistance of PDMS. In this study, we investigate the possibility of this TiOx nano-layer in providing surface anchoring groups on PDMS surfaces, enabling further functionalization. We treat PDMS samples cured at three different temperatures with AP-ALD and measure the hydrophilicity of the treated samples as an indicator of the presence of surface anchoring groups. We find that all the treated PDMS samples become hydrophilic right after the AP-ALD treatment. We further find that the AP-ALD-treated PDMS samples cured at 150°C and 200°C maintain their hydrophilicity, while the samples cured at 70°C become less hydrophilic over time. The presence of surface anchoring groups through TiOx nano-layer deposition on PDMS is further demonstrated and utilized by depositing gold nanoparticles (AuNPs) on the AP-ALD-treated samples. The samples exhibit visible light absorbance at 530 nm, a typical absorbance peak for AuNPs. In conclusion, this study demonstrates the use of nano-layers grown by AP-ALD to solve the two major problems of PDMS simultaneously, widening the PDMS applicability, especially for use in high-end applications such as catalysis and bio-sensing

Robust surface-subsurface modification of PDMS through atmospheric pressure atomic layer deposition

Polydimethylsiloxane (PDMS) has been widely employed as a material for microreactors and lab-on-a-chip technologies. However, in its applications, PDMS suffers from two major problems: its weak resistance against common organic solvents and its chemically non-functional surface. To overcome both issues, atmospheric pressure atomic layer deposition (AP-ALD) can be used to deposit an inorganic nano-layer (TiOx) on PDMS that in turn can be further functionalized. The inorganic nano-layer is previously communicated to durably increase the organic solvent resistance of PDMS. In this study, we investigate the possibility of this TiOx nano-layer in providing surface anchoring groups on PDMS surfaces, enabling further functionalization. We treat PDMS samples cured at three different temperatures with AP-ALD and measure the hydrophilicity of the treated samples as an indicator of the presence of surface anchoring groups. We find that all the treated PDMS samples become hydrophilic right after the AP-ALD treatment. We further find that the AP-ALD-treated PDMS samples cured at 150°C and 200°C maintain their hydrophilicity, while the samples cured at 70°C become less hydrophilic over time. The presence of surface anchoring groups through TiOx nano-layer deposition on PDMS is further demonstrated and utilized by depositing gold nanoparticles (AuNPs) on the AP-ALD-treated samples. The samples exhibit visible light absorbance at 530 nm, a typical absorbance peak for AuNPs. In conclusion, this study demonstrates the use of nano-layers grown by AP-ALD to solve the two major problems of PDMS simultaneously, widening the PDMS applicability, especially for use in high-end applications such as catalysis and bio-sensing