Shear induced fabrication of intertwined single walled carbon nanotube rings

Developing Novel Fabrication and Optimisation Strategies on Aggregation-Induced Emission Nanoprobe/Polyvinyl Alcohol Hydrogels for Bio-Applications

The current study describes a new technology, effective for readily preparing a fluorescent (FL) nanoprobe-based on hyperbranched polymer (HB) and aggregation-induced emission (AIE) fluorogen with high brightness to ultimately develop FL hydrogels. We prepared the AIE nanoprobe using a microfluidic platform to mix hyperbranched polymers (HB, generations 2, 3, and 4) with AIE (TPE-2BA) under shear stress and different rotation speeds (0-5 K RPM) and explored the FL properties of the AIE nanoprobe. Our results reveal that the use of HB generation 4 exhibits 30-times higher FL intensity compared to the AIE alone and is significantly brighter and more stable compared to those that are prepared using HB generations 3 and 2. In contrast to traditional methods, which are expensive and time-consuming and involve polymerization and post-functionalization to develop FL hyperbranched molecules, our proposed method offers a one-step method to prepare an AIE-HB nanoprobe with excellent FL characteristics. We employed the nanoprobe to fabricate fluorescent injectable bioadhesive gel and a hydrogel microchip based on polyvinyl alcohol (PVA). The addition of borax (50 mM) to the PVA + AIE nanoprobe results in the development of an injectable bioadhesive fluorescent gel with the ability to control AIEgen release for 300 min. When borax concentration increases two times (100 mM), the adhesion stress is more than two times bigger (7.1 mN/mm2) compared to that of gel alone (3.4 mN/mm2). Excellent dimensional stability and cell viability of the fluorescent microchip, along with its enhanced mechanical properties, proposes its potential applications in mechanobiology and understanding the impact of microstructure in cell studies.

High shear in situ exfoliation of 2D gallium oxide sheets from centrifugally derived thin films of liquid gallium

A diversity of two-dimensional nanomaterials has recently emerged with recent attention turning to the post-transition metal elements, in particular material derived from liquid metals and eutectic melts below 330 °C where processing is more flexible and in the temperature regime suitable for industry. This has been explored for liquid gallium using an angled vortex fluidic device (VFD) to fabricate ultrathin gallium oxide (Ga2O3) sheets under continuous flow conditions. We have established the nanosheets to form highly insulating material and have electrocatalytic activity for hydrogen evolution, with a Tafel slope of 39 mV dec-1 revealing promoting effects of the surface oxidation (passivation layer).

High shear spheroidal topological fluid flow induced coating of polystyrene beads with C60 spicules

Spheroidal spicular like topological fluid flow in an angled vortex fluidic device (VFD) housing a 20 mm diameter tube with a hemispherical base rotating at 4k rpm and tilted at 45° is effective in reducing the thermodynamic equilibrium concentration of fullerene C60 in toluene, with the formation of spicules of the material under continuous flow processing. Under the same operational conditions in the presence of polystyrene beads 2 to 6 μm in diameter, spicules of C60ca. 150 nm in length grow on their surfaces. This establishes that the spheroidal topological fluid flow in the VFD prevails while enveloping spheroidal like particles of such size.

Vertically aligned laser sliced MWCNTs

Applications of multi-walled carbon nanotubes (MWCNTs) benefit from the availability of specific lengths of the material while keeping the outer walls pristine, for example, for applications requiring vertically aligned tubes. To this end, a simple and effective continuous flow 'top down' process to control the length of sliced MWCNTs has been developed using a vortex fluidic device (VFD) coupled with a 1064 nm pulse laser, with the process in the absence of chemicals and any auxiliary substances. Three different length distributions of the sliced MWCNTs, centered at 75 ± 2.1 nm, 300 ± 1.8 nm and 550 ± 1.4 nm, have been generated with the length depending on the VFD operating parameters and laser energy, with the processing resulting in a decrease in side wall defects of the material. We also show the ability to vertically self assemble short MWCNTs on a silicon substrate with control of the surface density coverage using a simple dipping and rinsing method.

High-Yield Continuous-Flow Synthesis of Spheroidal C60@Graphene Composites as Supercapacitors

Graphene spheres confining fullerene C60 are quantitatively formed under high-shear and continuous-flow processing using a vortex fluidic device (VFD). This involves intense micromixing a colloidal suspension of graphite in DMF and an o-xylene solution of C60 at room temperature in the absence of surfactants and other auxiliary substances. The diameters of the composite spheres, C60@graphene, can be controlled with size distributions ranging from 1.5 to 3.5 μm, depending on the VFD operating parameters, including rotational speed, flow rate, relative ratio of C60 to graphite, and the concentration of fullerene. An electrode of the composite material has high cycle stability, with a high areal capacitance of 103.4 mF cm-2, maintaining its capacitances to 24.7 F g-1 and 86.4 mF cm-2 (83.5%) at a high scan rate of 100 mV s-1.

Vortex fluidic mediated transformation of graphite into highly conducting graphene scrolls

Two-dimensional graphene has remarkable properties that are revolutionary in many applications. Scrolling monolayer graphene with precise tunability would create further potential for niche applications but this has proved challenging. We have now established the ability to fabricate monolayer graphene scrolls in high yield directly from graphite flakes under non-equilibrium conditions at room temperature in dynamic thin films of liquid. Using conductive atomic force microscopy we demonstrate that the graphene scrolls form highly conducting electrical contacts to highly oriented pyrolytic graphite (HOPG). These highly conducting graphite-graphene contacts are attractive for the fabrication of interconnects in microcircuits and align with the increasing interest in building all sp²-carbon circuits. Above a temperature of 450 °C the scrolls unravel into buckled graphene sheets, and this process is understood on a theoretical basis. These findings augur well for new applications, in particular for incorporating the scrolls into miniaturized electronic devices.

Neutron imaging and modelling inclined vortex driven thin films

The vortex fluidic device (VFD) is a thin film microfluidic platform which has a wide range of applications in synthesis and other areas of science, and it is important to understand the nature of the thin film of liquid in its inclined rapidly rotating tube. Neutron imaging has been used to determine the thickness of the film in a quartz tube with its shape modelled mathematically, showing good agreement between the model and experiments. The resultant equations are useful for studying VFD mediated processing in general, for which the optimal tilt angle of the tube is typically 45°. This includes its utility for the intelligent scale-up of organic syntheses, as demonstrated in the present study by the scaling up of an imine and amide synthesis to >1 g/min.

Laser-Ablated Vortex Fluidic-Mediated Synthesis of Superparamagnetic Magnetite Nanoparticles in Water Under Flow

Selective formation of only one iron oxide phase is a major challenge in conventional laser ablation process, as is scaling up the process. Herein, superparamagnetic single-phase magnetite nanoparticles of hexagonal and spheroidal-shape, with an average size of ca. 15 nm, are generated by laser ablation of bulk iron metal at 1064 nm in a vortex fluidic device (VFD). This is a one-step continuous flow process, in air at ambient pressure, with in situ uptake of the nanoparticles in the dynamic thin film of water in the VFD. The process minimizes the generation of waste by avoiding the need for any chemicals or surfactants and avoids time-consuming purification steps in reducing any negative impact of the processing on the environment.

Controlling the growth of fullerene C60 cones under continuous flow

Micromixing of an o-xylene solution of C60 with N-N-dimethylformamide (DMF) at room temperature under continuous flow in a vortex fluidic device (VFD) results in the formation of symmetrical right cones in high yield with diameters 0.5 to 2.5 μm, pitch angle 25° to 55° and wall thickness 120 to 310 nm. Their formation is in the absence of surfactants and any other reagents, and is scalable. The cones are formed at specific operating parameters of the VFD, including rotational speed, flow rate and concentration, and varying these results in other structures such as grooved fractals. Other aromatic solvents in place of o-xylene results in the formation of rods, spicules and prisms, respectively for m-xylene, p-xylene and mesitylene.

Laser irradiated vortex fluidic mediated synthesis of luminescent carbon nanodots under continuous flow

High shear vortex fluidics coupled with NIR affords luminescent carbon dots as a scalable process.

Vortex Fluidic Chemical Transformations

Driving chemical transformations in dynamic thin films represents a rapidly thriving and diversifying research area. Dynamic thin films provide a number of benefits including large surface areas, high shearing rates, rapid heat and mass transfer, micromixing and fluidic pressure waves. Combinations of these effects provide an avant-garde style of conducting chemical reactions with surprising and unusual outcomes. The vortex fluidic device (VFD) has proved its capabilities in accelerating and increasing the efficiencies of numerous organic, materials and biochemical reactions. This Minireview surveys transformations that have benefited from VFD-mediated processing, and identifies concepts driving the effectiveness of vortex-based dynamic thin films.

Fluid dynamic lateral slicing of high tensile strength carbon nanotubes

Lateral slicing of micron length carbon nanotubes (CNTs) is effective on laser irradiation of the materials suspended within dynamic liquid thin films in a microfluidic vortex fluidic device (VFD). The method produces sliced CNTs with minimal defects in the absence of any chemical stabilizers, having broad length distributions centred at ca 190, 160 nm and 171 nm for single, double and multi walled CNTs respectively, as established using atomic force microscopy and supported by small angle neutron scattering solution data. Molecular dynamics simulations on a bent single walled carbon nanotube (SWCNT) with a radius of curvature of order 10 nm results in tearing across the tube upon heating, highlighting the role of shear forces which bend the tube forming strained bonds which are ruptured by the laser irradiation. CNT slicing occurs with the VFD operating in both the confined mode for a finite volume of liquid and continuous flow for scalability purposes.

One-step ligand exchange and switching from hydrophobic to water-stable hydrophilic superparamagnetic iron oxide nanoparticles by mechanochemical milling

Mechanochemistry permits rapid solvent-free exchange of surface ligands on superparamagnetic iron oxide nanoparticles (IONPs), enabling control of surface properties.

Manipulating three-dimensional gel network entanglement by thin film shearing

A novel method of combining thin-film shearing with SANS resulted in complete disruption of 3-D network of fluorous bis-urea gel. In contrast, non-fluorinated analogue undergoes partial disruption which emphasizes the resistance of non-fluorous bis-urea gelators towards shear.

Microencapsulation of bacterial strains in graphene oxide nano-sheets using vortex fluidics

Microencapsulation of bacterial cells with different shapes in graphene oxide (GO) layers is effective using a vortex fluidic device, with the bacterial cells showing restricted cellular growth with their biological activity sustained.

Strong cation···π interactions promote the capture of metal ions within metal-seamed nanocapsule

Thallium ions are transported to the interior of gallium-seamed pyrogallol[4]arene nanocapsules. In comparison to the capture of Cs ions, the extent of which depends on the type and position of the anion employed in the cesium salt, the enhanced strength of Tl···π vs Cs···π interactions facilitates permanent entrapment of Tl(+) ions on the capsule interior. "Stitching-up" the capsule seam with a tertiary metal (Zn, Rb, or K) affords new trimetallic nanocapsules in solid state.