Vortex fluidic regulated phospholipid equilibria involving liposomes down to sub-micelle size assemblies.

Conventional channel-based microfluidic platforms have gained prominence in controlling the bottom-up formation of phospholipid based nanostructures including liposomes. However, there are challenges in the production of liposomes from rapidly scalable processes. These have been overcome using a vortex fluidic device (VFD), which is a thin film microfluidic platform rather than channel-based, affording ∼110 nm diameter liposomes. The high yielding and high throughput continuous flow process has a 45° tilted rapidly rotating glass tube with an inner hydrophobic surface. Processing is also possible in the confined mode of operation which is effective for labelling pre-VFD-prepared liposomes with fluorophore tags for subsequent mechanistic studies on the fate of liposomes under shear stress in the VFD. In situ small-angle neutron scattering (SANS) established the co-existence of liposomes ∼110 nm with small rafts, micelles, distorted micelles, or sub-micelle size assemblies of phospholipid, for increasing rotation speeds. The equilibria between these smaller entities and ∼110 nm liposomes for a specific rotational speed of the tube is consistent with the spatial arrangement and dimensionality of topological fluid flow regimes in the VFD. The prevalence for the formation of ∼110 nm diameter liposomes establishes that this is typically the most stable structure from the bottom-up self-assembly of the phospholipid and is in accord with dimensions of exosomes.

Vortex fluidics mediated non-covalent physical entanglement of tannic acid and gelatin for entrapment of nutrients.

We have developed a simple process for the entrapment of nutrients in shear stress induced non-covalent physically entangled tannic acid-gelatin gel in a thin film vortex fluidic device (VFD) operating under continuous flow. This allows control of the porosity and surface area of the pores in order to improve the nutrient entrapment capacity. The VFD microfluidic platform simplifies the processing procedure of physically entangled biopolymers, as a time and cost saving one-step process devoid of any organic solvents, in contrast to the conventional homogenization process, which is also inherently complex, involving multiple-step processing. Moreover, the use of homogenization (as a benchmark to entrap nutrients) afforded much larger porosity and surface area of pores, with lower entrapment capacity of nutrients. Overall, the VFD processing provides a new alternative, bottom-up approach for easy, scalable processing for materials with a high nutrient entrapment capacity.

Continuous Flow Copper Laser Ablation Synthesis of Copper(I and II) Oxide Nanoparticles in Water.

Copper(I) oxide (Cu2O) nanoparticles (NPs) are selectively prepared in high yields under continuous flow in a vortex fluidic device (VFD), involving irradiation of a copper rod using a pulsed laser operating at 1064 nm and 600 mJ. The plasma plume generated inside a glass tube (20 mm O.D.), which is rapidly rotating (7.5 k rpm), reacts with the enclosed air in the microfluidic platform, with then high mass transfer of material into the dynamic thin film of water passing up the tube. The average size of the generated Cu2ONPs is 14 nm, and they are converted to copper(II) oxide (CuO) nanoparticles with an average diameter of 11 nm by heating the as-prepared solution of Cu2ONPs in air at 50 °C for 10 h.

Inverted vortex fluidic exfoliation and scrolling of hexagonal-boron nitride.

Exfoliation or scrolling of hexagonal boron nitride (h-BN) occurs in a vortex fluidic device (VFD) operating under continuous flow, with a tilt angle of -45° relative to the horizontal position. This new VFD processing strategy is effective in avoiding the build-up of material that occurs when the device is operated using the conventional tilt angle of +45°, where the h-BN precursor and scrolls are centrifugally held against the wall of the tube. At a tilt angle of -45° the downward flow aided by gravity facilitates material exiting the tube with the exfoliation of h-BN and formation of h-BN scrolls then optimized by systematically varying the other VFD operating parameters, including flow rate and rotational speed, along with concentration of h-BN and the choice of solvent. Water was the most effective solvent, which enhances the green chemistry metrics of the processing.

Dynamic thin film mediated slicing of boron nitride nanotubes.

A method has been developed to slice boron nitride nanotubes BNNTs under continuous flow in a vortex fluidic device (VFD), along with a method to partially purify the as received BNNT containing material. The latter involves heating the BNNTs to 600 °C followed by dispersing in a 1 : 3 isopropyl alcohol (IPA) and water mixture at 100 °C. The VFD mediated slicing of the BNNTs comprises irradiating the rapidly rotating glass tube (20 mm OD) with a pulsed Nd:YAG laser. Systematically exploring the operating parameter space of the VFD established slicing of ca. 200 µm long purified BNNTs down to 340 nm to 400 nm, in ca. 53% yield, in a 1 : 1 mixture of IPA and water, in the absence of reagents/harsh chemicals, at a flow rate of 0.45 mL min-1, a concentration of 0.1 mg mL-1 BNNTs and an 8.5k rpm rotational speed, with the pulsed laser operating at 1064 nm and 250 mJ per pulse.

Vortex Fluidic Mediated Synthesis of Macroporous Bovine Serum Albumin-Based Microspheres.

Macroporous bovine serum albumin (BSA) nanoparticles with controllable diameter were readily fabricated in a rapidly rotating angled glass tube in a vortex fluidic device (VFD). Systematically varying the rotational speed and the ratio of BSA, ethanol, and glutaraldehyde led to conditions for generating ca. 600 nm diameter macroporous particles that have intrinsic fluorescence emission at 520 nm when excited at 490 nm. The presence of the macropores increased the absorption efficiency of rhodamine B with potential applications for drug delivery purpose, compared with BSA nanoparticles having surfaces devoid of pores. Further control over the size of BSA nanoparticles occurred in the presence of C-phycocyanin protein during the VFD processing, along with control of their shape, from spheres to pockets, as established in exploring the parameter space of the microfluidic device.