Envied by many scientists, delicate multichannel (or multichamber) tubular structures have been adopted by a number of animals in long-term evolution. For example, feathers of many birds are of multichannel inner structure. It could reduce weight by increasing friction with air and serve as heat-shields from intense solar radiation. 1 To survive in an extremely formidable polar environment, pelts of some polar homeothermic species (e.g., polar bear) show excellent thermoinsulation properties which also benefit from their hair with multichamber structures. 2 These attractive features of nature are all results from the unique multichannel tubular inner structures.Partially similar with nature, traditional nanotubes with a single inner channel have attracted considerable interest for their broad applications. 3 Accordingly, various strategies have been proposed for building these materials. 4 Recently, another promising coaxial electrospinning method has been developed for preparing ultralong nanotubes.  Electrospinning is a versatile top-down method for manufacturing 1-D nanomaterials 9 with various applications. 10,11 Coaxial electrospinning is an evolution of electrospinning, which is based on a spinneret consisting of two coaxial capillaries with different diameters. By co-electrospinning two fluids with such special spinneret, nanotubes or core-shell nanofibers can be prepared.  Although methods for production of single channel nanotubes have been well established, artificial mimic multichannel tubular structures of nature in micro-to nanometer scale are still a giant challenge. To meet the emerging needs of multifunctional, integrative, and miniature devices, micro/nanomaterials with more complex inner structures are urgently expected.In this communication, we describe a multifluidic compoundjet electrospinning technique for the first time that could fabricate bio-mimic hierarchical multichannel microtubes in a facile and straightforward way. The experimental setup of the multifluidic compound-jet electrospinning is sketched in Figure 1a, where the three-channel tube (TCT) fabrication system is demonstrated as an example. Three metallic capillaries embedded in a plastic syringe were arranged at three vertexes of an equilateral triangle. These conductive metallic inner capillaries serve as inner fluid vessels and electrode at the same time. Two immiscible viscous liquids were fed separately to the three inner capillaries and an outer syringe in an appropriate flow rate. An ethanol solution of Ti(OiPr) 4 and poly(vinyl pyrrolidone) 6 served as outer liquid, while a commercially available innocuous paraffin oil was chosen for inner liquid. After a compound fluidic electrospinning process, a fibrous film was collected on the counter electrode. By removing the organics of as-prepared products through calcination, TiO 2 TCT was obtained. Figure 1b is a side-view image of the sample taken by field emission scanning electron microscopy (SEM), which exposes the cross section of the TCT. It c...
The interaction of covalently coupled hyaluronic acid, alginic acid, and pectic acid with proteins, cells (hematopoietic KG1a and Jurkat cells), and marine organisms (algal zoospores and barnacle cypris larvae) is compared. In contrast to cells and proteins for which such polysaccharide coatings are known for their antiadhesive properties, marine algal spores and barnacle cyprids were able to colonize the surfaces. Of the three polysaccharides, hyaluronic acid showed the lowest settlement of both Ulva zoopores and barnacles. Photoelectron spectroscopy reveals that the polysaccharide coatings tend to bind bivalent ions, such as calcium, from salt water. Such pretreatment with a high salinity medium significantly changes the protein and hematopoietic cell resistance of the surfaces. Complexation of bivalent ions is therefore considered as one reason for the decreased resistance of polysaccharide coatings when applied in the marine environment.
Reversible switching of the mobility of a water microdroplet between rollable and pinned simply by changing the temperature is realized by coordination of the phase transition of a side‐chain liquid‐crystal polymer (SCLCP) with optimized surface roughness of a superhydrophobic surface. The responsive surface has potential applications in microreactor design and microfluidic control systems.
The interaction of spores of Ulva with bioinspired structured surfaces in the nanometer–micrometer size range is investigated using a series of coatings with systematically varying morphology and chemistry, which allows separation of the contributions of morphology and surface chemistry to settlement (attachment) and adhesion strength. Structured surfaces are prepared by layer‐by‐layer spray‐coating deposition of polyelectrolytes. By changing the pH during application of oppositely charged poly(acrylic acid) and polyethylenimine polyelectrolytes, the surface structures are systematically varied, which allows the influence of morphology on the biological response to be determined. In order to discriminate morphological from chemical effects, surfaces are chemically modified with poly(ethylene glycol) and tridecafluoroctyltriethoxysilane. This chemical modification changes the water contact angles while the influence of the morphology is retained. The lowest level of settlement is observed for structures of the order 2 µm. All surfaces are characterized with respect to their wettability, chemical composition, and morphological properties by contact angle measurement, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy.
Achieving nanocomposites with simultaneous highly anisotropic thermal and electrical conductivities using carbon materials remains challenging as carbon material tends to form random networks in nanocomposites. Here, highly anisotropic and flexible graphene@naphthalenesulfonate (NS)/poly(vinyl alcohol) (GN/PVA) nanocomposites were fabricated using a layer-by-layer scraping method with flat graphene as the starting functional filler. NS acted as a bond bridge for linking the graphene (π−π interaction) and PVA (hydrogen bond). The results showed well-dispersed graphene in the nanocomposites while maintaining flat morphology with uniform in-plane orientation. The as-fabricated nanocomposites exhibited highly anisotropic thermal and electrical conductivities. The in-plane and out-of-plane thermal conductivities of the nanocomposite prepared with 10.0 wt % graphene reached 13.8 and 0.6 W m −1 K −1 , and in-plane and out-of-plane electrical conductivities were 10 −1 and 10 −10 S cm −1 , respectively. This indicated highly anisotropic thermal and electrical conductivities. Furthermore, the nanocomposites showed elevated flexibility and tensile strength from 42.0 MPa for pure PVA to 110.0 MPa for GN-5.0 wt %/PVA. In sum, the proposed strategy is effective for the preparation of nanocomposites with high flexibility, as well as superior anisotropic thermal and electrical conductivities.
This paper presents a simultaneous microscopic structure characteristic of shape-memory (SM) poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) inverse opals together with a bulk PVDF-HFP by scanning electron microscopy (SEM). The materials show a thermo-sensitive micro-SM property, accompanied with a reversible and modulated optical property. The introduction of the inverse opal structure into the shape-memory polymer material renders a recognition ability of the microstructure change aroused from complex environmental signals by an optical signal, which can be simultaneously detected by SEM. Furthermore, this feature was applied as a reversible write/erase of fingerprint pattern through the press-stimulus and solvent-induced effect, together with the changes of morphology/optical signal. This micro-SM property can be attributed to the shrink/swell effect of the polymer chain from external stimuli combined with the microscopic structure of inverse opals. It will trigger a promising way toward designing reversible micro-deformed actuators.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.