Durable and biocompatible superhydrophobic surfaces are of significant potential use in biomedical applications. Here, a nonfluorinated, elastic, superhydrophobic film that can be used for medical wound dressings to enhance their hemostasis function is introduced. The film is formed by titanium dioxide nanoparticles, which are chemically crosslinked in a poly(dimethylsiloxane) (PDMS) matrix. The PDMS crosslinks result in large strain elasticity of the film, so that it conforms to deformations of the substrate. The photocatalytic activity of the titanium dioxide provides surfaces with both self‐cleaning and antibacterial properties. Facile coating of conventional wound dressings is demonstrated with this composite film and then resulting improvement for hemostasis. High gas permeability and water repellency of the film will provide additional benefit for medical applications.
Controlling
the droplet evaporation on surfaces is desired to get
uniform depositions of materials in many applications, for example,
in two- and three-dimensional printing and biosensors. To explore
a new route to control droplet evaporation on surfaces and produce
asymmetric particles, sessile droplets of aqueous dispersions were
allowed to evaporate from surfaces coated with oil films. Here, we
applied 1–50 μm thick films of different silicone oils.
Two contact lines were observed during droplet evaporation: an apparent
liquid–liquid–air contact line and liquid–liquid–solid
contact line. Because of the oil meniscus covering part of the rim
of the drop, evaporation at the periphery is suppressed. Consequently,
the droplet evaporates mainly in the central region of the liquid–air
interface rather than at the droplet’s edge. Colloidal particles
migrate with the generated upward flow inside the droplet and are
captured by the receding liquid–air interface. A uniform deposition
ultimately forms on the substrate. With this straightforward approach,
asymmetric supraparticles have been successfully fabricated independent
of particle species.
Polydimethylsiloxane
(PDMS) can be linked to the surface of metal-oxide photocatalysts
by immersion and UV illumination. The surfaces become hydrophobic
and keep their hydrophobicity even under extended UV exposure. Titanium
dioxide (TiO
2
) is a prominent example of a metal-oxide
photocatalyst. Here, we studied the influence of a grafted PDMS layer
on the photocatalytic activity and wetting properties of TiO
2
. By varying the molecular weight of PDMS, we controlled the thickness
of the polymer layer from 0.6 to 5.5 nm. We recommend a PDMS molecular
weight of 6.0 kDa. It leads to a grafted PDMS layer thickness of 2.2
nm, a receding contact angle of 94°, a low contact angle
hysteresis of 9°, and the layer is still photocatalytically active.
Giant unilamellar vesicles (GUVs)
are model membrane systems consisting
of a single lipid bilayer separating an inner lumen from the outer
solution, with dimensions comparable to that of eukaryotic cells.
The importance of these biomimetic systems has recently grown with
the development of easy and safe methods to assemble GUVs from complex
biorelevant compositions. However, size and position control is still
a key challenge for GUV formation and manipulation. Here, a gel-assisted
formation method is introduced, able to produce arrays of giant unilamellar
anchored vesicles (GUAVs) with a predetermined narrow size distribution.
The approach based on micropatterned gel substrates of cross-linked
poly(
N
-isopropylacrylamide) allows performing parallel
measurements on thousands of immobile unilamellar vesicles. Such power
and flexibility will respond to the growing need for developing platforms
of biomimetic constructs from cell-sized single bilayers.
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