Narrow Results

When a drop impacts onto a solid surface, it spreads out into a pancake shape and often forms a dry-spot at the center of the drop. We show that this dewetting at the center is sometimes produced by a small bubble of air which is entrapped on the substrate under the center of the drop. Capillary waves are generated on the surface of the pancake, during the rebounding of the lamellar edge. As these capillary waves converge at the axis of symmetry, their amplitude grows in size until a wave trough touches and merges with the entrapped bubble. This opens up a dry-patch at the center of the splash. We use state-of-the art high-speed video imaging to study this process, for a drop impacting onto a Perspex surface. The imaging is done by looking through the bottom plate to reveal the detailed motions of the capillary waves.

In this paper, the effect of dewetted gold nanoparticles (AuNPs) on hexagonal boron nitride (hBN) is discussed along with the changes in surface plasmon resonance (SPR). Au is sputtered on monolayer hBN/SiO₂/Si substrate for a varied duration and subjected to thermal annealing. Monolayer hBN is verified by spectroscopic ellipsometry using the Tauc–Lorentz model, while the AuNPs are modeled using a combination of Gauss, Cody–Lorentz, and Tanguy dispersion laws. Sputtering of Au on hBN/SiO₂/Si results in a film-like layer compared to the one on SiO₂/Si. Before annealing, the improved uniformity of Au on hBN/SiO₂/Si diminished the SPR wavelength, ${\lambda }_{\mathrm{\text{spr}}}$, when the sputter duration exceeded 30 s, much sooner compared to 120 s from the one on SiO₂/Si. After annealing, the ${\lambda }_{\mathrm{\text{spr}}}$ is vibrant for all samples around 2.3 eV. Au dewetted more on hBN due to higher surface tension. Large dewetted AuNPs supported by hBN result in higher photon extinction at ${\lambda }_{\mathrm{\text{spr}}}$. The longest sputter duration of 120 s on hBN/SiO₂/Si (mean size 53 nm) exhibited an 11.2% higher extinction coefficient compared to the one on SiO₂/Si (mean size 39.6 nm). Findings support the advantages of preparing plasmonic AuNPs by dewetting on monolayer hBN.

The growth of high-quality continuous film of graphene on less than $1\mu$m-thick Cu film is proven to be a challenging task due to the solid-state dewetting of Cu during the high-temperature chemical vapor deposition (CVD) process. In this paper, we introduce the use of nanostructured black Si (b-Si) as a template for Cu evaporation to mitigate the dewetting of Cu thin film. Using a cold-wall CVD system at a process temperature of 825${}^{\circ }$C, even Cu thickness, $t_{\mathrm{\text{Cu}}}=600$ nm on polished SiO₂/Si substrate is poor for maintaining Cu as a continuous film. If the polished SiO₂/Si is replaced with SiO₂/b-Si, the minimum $t_{\mathrm{\text{Cu}}}=400$ nm is sufficient. According to the Cu trapping mechanism, moving Cu particle is trapped in the nanostructured trenches of SiO₂/b-Si during annealing and CVD growth processes. Continuous monolayer graphene with a grain size of $\sim 1\mu$m without defect is obtained on Cu/SiO₂/b-Si substrate. The improved adhesion of Cu to the SiO₂/b-Si enables dry-transfer of graphene by mechanical peeling using a polyvinyl alcohol (PVA) film. Our solution is promising for obtaining flat graphene and a recyclable Cu/SiO₂/b-Si substrate.

The fluorescence behavior of 3,3′diethyl-thiacarbocyanine iodide in micrometer-sized polystyrene droplets, or "domes" on glass substrates was investigated. The samples were prepared by casting dilute polymer/dye solutions onto the substrates. A dewetting process leads to the formation of small polymer domes with a diameter of 1–100 μm and a height of 100 nm to several μm. Fluorescence microscopy shows that the dye is incorporated into these polymer domes. It was found that the absorption and fluorescence spectra depend on the size of the polymer domes. Larger domes show red-shifted fluorescence spectra.

We study the kinetics of specific adhesion of giant vesicles on complemetary (bilayer-decorated) solid surfaces. Tensed vesicles exhibit a single adhesion zone that grows slowly. Floppy vesicles adhere via many small adhesion spots that grow and fuse, merging finally into a large adhesive zone. Using approaches derived from Ref. 12, we show how the progressive mobilization of adhesive molecules (diffusing toward the patch) can explain our experimental observations.

Cell-sized lipid vesicles (CLVs) have shown great promise for therapeutic and artificial cell applications, but their fragility and short shelf life has hindered widespread adoption and commercial viability. We present a method to circumvent the storage limitations of CLVs such as giant unilamellar vesicles (GUVs) and single-compartment multisomes (SCMs) by storing them in a double emulsion precursor form. The double emulsions can be stored for at least 8 months and readily converted into either GUVs or SCMs at any time. In this study, we investigate the interfacial parameters responsible for this morphological change, and we also demonstrate the therapeutic potential of CLVs by utilizing them to present a transmembrane protein, neuroligin-2, to pancreatic $\beta$-cells, forming cell-cell synapses that stimulate insulin secretion and cellular growth.

The fluorescence behavior of 3,3'diethyl-thiacarbocyanine iodide in micrometer-sized polystyrene droplets, or "domes" on glass substrates was investigated. The samples were prepared by casting dilute polymer/dye solutions onto the substrates. A dewetting process leads to the formation of small polymer domes with a diameter of 1–100 μm and a height of 100 nm to several μm. Fluorescence microscopy shows that the dye is incorporated into these polymer domes. It was found that the absorption and fluorescence spectra depend on the size of the polymer domes. Larger domes show red-shifted fluorescence spectra.