Sub-Micron Moulding Topological Mass Transport Regimes in Angled Vortex Fluidic Flow

Abstract

<b>Induced mechanical energy in a thin film of liquid in an inclined rapidly rotating tube in the vortex fluidic device (VFD) can be harnessed for generating non-equilibrium conditions, which are optimal at 45<sup>o</sup> tilt angle, but the nature of the fluid flow is not understood. Through understanding that the fluid exhibits resonance behaviours from the confining boundaries of the glass surface and the meniscus that determines the liquid film thickness, we have established specific topological mass transport regimes. These topologies have been established through materials processing, as circular flow normal to the surface of the tube, double-helical flow across the thin film, and spicular flow, a transitional region where both effects contribute. This includes new phenomenological shear stressed crystallization and molecular drilling. The manifestation of these patterns has been observed by monitoring mixing times, temperature profiles, and film thickness against rotational speed of liquids in the tube. The grand sum of the different behavioural regimes is a general fluid flow model that accounts for all processing in the VFD at an optimal tilt angle of 45<sup>o</sup>, and provides a new concept in the fabrication of novel nanomaterials and controlling the organisation of matter.</b>

Vortex Fluidic-Mediated Fabrication of Fast Gelated Silica Hydrogels with Embedded Laccase Nanoflowers for Real-Time Biosensing under Flow

“…As shown, BNFs reduced from 5 to 2 μm with more tightly packed petals by increasing the rotational speed from 3000 to 7000 rpm (1.5 mL BSA in 10 mM PBS at 0.1 mg/mL; 10 μL CuSO 4 ), in accordance with a reduction in the dimension of the double helical topological flow arising from eddies from the Faraday waves being twisted. 17 By systematically exploring the concentration effects (Figure S6) and a wide range of different molar ratios between PBS and CuSO 4 , we established that 13:1 (1.5 mL 0.1 mg/mL BSA in 10 mM PBS; 10 μL CuSO 4 ) generates the most homogeneous and monodispersed BNFs (Figures S7 and S8). On the basis of the EE for the BNFs prepared under different conditions, the concentration of proteins in the system has a greater impact on the EE than the rotational speed, with the best outcome (88% EE) observed when adding a smaller amount of protein, 0.02 mg/mL for BSA (Figure 1c,d), which is consistent with previous findings.…”

“…4 Toroidal-shaped BSA-Cu 2+ crystals (1.5 μm in diameter with 0.58 μm void diameter) prevail after only 2 min with their formation representing localized areas of high shear associated with double helical topological fluid flow arising from eddies from Faraday waves being twisted by the Coriolis inertial forces from the cylindrical shape of the tube. 17 They occur across the rotational landscape in the VFD when the tilt angle is 45 o , but with reduced dimensionality for increasing the rotational speed, 17 as shown in Figure 1a. The shear stress associated with this double helical fluid flow presumably facilitates protein molecule complexation with Cu 2+ , noting that the shear stress generated in the VFD is effective in promoting nucleation and growth of nanoparticles.…”

“…These observations indicate that the growth mechanism of BNFs, and the intermediate toroidal structures, within the VFD is dramatically different from those formed using conventional batch processing. The formation of the NFs is initiated from a toroid driven by the double helical flow striking the surface of the VFD tube where there is high heat and mass transfer, 17 with the protein molecules uniformly distributed within the confines of the toroids. For 30 min processing, which results in spheroidal BNFs, the size of the BNFs can be manipulated by changing the rotational speed of the VFD (Figure 1a and Figure S2).…”

“…A similar situation has been observed when alkaline phosphatase displayed an average 6 fold acceleration in a VFD-mediated reaction, 23 but once being immobilized on the glass surface, the VFD-mediated enzymatic ac-celeration is not observed. 14,25 This results in high mass transfer (increase in average velocity of molecules in the system) 17 under conditions beyond diffusion control. For an enzyme like laccase, such conditions could accelerate removal of the product from the enzyme active site, decreasing product inhibition.…”

“…The shear stress associated with this double helical fluid flow presumably facilitates protein molecule complexation with Cu 2+ , noting that the shear stress generated in the VFD is effective in promoting nucleation and growth of nanoparticles. 17 Complexation predominantly involves coordination of the amide groups in the protein backbone 4 and the nucleation of Cu 3 (PO 4 ) 2 crystals forming stacked petal layers radiating from the center, thereby filling the void. Processing for 10 min in the VFD affords slightly larger toroidal structures, with a buildup of material around the surface of the first formed microtoroids with the void space reducing in size (to 0.25 μm in diameter) with the overall diameter of the toroid structures becoming about 2 μm (Figure 1b).…”