Harnessing Electric Fields for Microfluidics – From Lightning Sparks to Tiny Tornadoes

The dominance of surface tension and viscous effects over body forces such as inertia, gravity or centrifugal force makes fluid actuation and particle manipulation at microscale dimensions extremely difficult. We demonstrate the possibility of exploiting electric fields to drive unstable turbulent-like flows for micromixing and complex flows for efficient particle separation and concentration. In particular, the ions resulting from the breakdown of air surrounding a theoretically singular sharp electrode tip due to corona discharge is employed to accelerate the air towards the surface of a liquid in a cylindrical microchamber. Through interfacial shear, the surface liquid layer is recirculated to produce a Batchelor-type flow within the chamber that spirals suspended colloidal particles to a stagnation point at the bottom no-slip plane. We show the use of this technology for rapid and efficient separation of red blood cells from plasma for the development of miniaturised point-of-care diagnostics. Such liquid flows also become unstable at high applied voltages and frequencies leading to the generation of vortices that span a cascade of length scales, which can be exploited for micromixing

Driving Cell Seeding Using Surface Acoustic Wave Fluid Actuation

In this paper, we investigate the ability to drive fluid streaming via a surface acoustic wave (SAW) into a porous bioscaffold structure, and to exploit this effect to deliver fluorescent particles/yeast cells into the scaffold as a potential rapid and efficient method for cell seeding in tissue engineering. The results demonstrate that the seeding process takes approximately 10 seconds, much shorter than that if the cell suspension were to perfuse through the scaffold under the effects of gravity alone (approximately 30 mins). By increasing the input power, both the velocity of the fluid flow and the particle seeding efficiency can be enhanced. At 560 mW, fluid velocities of the order 10 mm/s were achieved; in this case, the particle/yeast seeding efficiency is around 92%. In addition to rapid seeding, the SAW streaming induced perfusion is observed to significantly improve the uniformity of the scaffold cell distribution due to greater penetration into the scaffold. Finally, we verify using a methylene violet staining procedure that 80% of the yeast cells seeded by the SAW method within the scaffold remained viable

Extensional viscosity of copper nanowire suspensions in an aqueous polymer solution

Suspensions of copper nanowires are emerging as new electronic inks for next-generation flexible electronics. Using a novel surface acoustic wave driven extensional flow technique we are able to perform currently lacking analysis of these suspensions and their complex buffer. We observe extensional viscosities from 3 mPa$\cdot$s (1 mPa$\cdot$s shear viscosity) to 37.2 Pa$\cdot$s via changes in the suspension concentration, thus capturing low viscosities that have been historically very challenging to measure. These changes equate to an increase in the relative extensional viscosity of nearly 12,200 times at a volume fraction of just 0.027. We also find that interactions between the wires and the necessary polymer additive affect the rheology strongly. Polymer-induced elasticity shows a reduction as the buffer relaxation time falls from 819 to 59 $\mu$s above a critical particle concentration. The results and technique presented here should aid in the future formulation of these promising nanowire suspensions and their efficient application as inks and coatings.Comment: 7 pages, 5 figures, under review for Soft Matter RS

Motility induced changes in viscosity of suspensions of swimming microbes in extensional flows

Suspensions of motile cells are model systems for understanding the unique mechanical properties of living materials which often consist of ensembles of self-propelled particles. We present here a quantitative comparison of theory against experiment for the rheology of such suspensions. The influence of motility on viscosities of cell suspensions is studied using a novel acoustically-driven microfluidic capillary-breakup extensional rheometer. Motility increases the extensional viscosity of suspensions of algal pullers, but decreases it in the case of bacterial or sperm pushers. A recent model [Saintillan, Phys. Rev. E, 2010, 81:56307] for dilute active suspensions is extended to obtain predictions for higher concentrations, after independently obtaining parameters such as swimming speeds and diffusivities. We show that details of body and flagellar shape can significantly determine macroscale rheological behaviour.Comment: 12 pages, 1 appendix, 7 figures, submitted to Soft Matter - under revie

Pulmonary Deposition of Radionucleotide-Labeled Palivizumab: Proof-of-Concept Study

Objective: Current prevention and/or treatment options for respiratory syncytial virus (RSV) infections are limited as no vaccine is available. Prophylaxis with palivizumab is very expensive and requires multiple intramuscular injections over the RSV season. Here we present proof-of-concept data using nebulized palivizumab delivery as a promising new approach for the prevention or treatment of severe RSV infections, documenting both aerosol characteristics and pulmonary deposition patterns in the lungs of lambs. Design: Prospective animal study. Setting: Biosecurity Control Level 2-designated large animal research facility at the Murdoch Children’s Research Institute, Melbourne, Australia. Subjects: Four weaned Border-Leicester/Suffolk lambs at 5 months of age. Interventions: Four lambs were administered aerosolized palivizumab conjugated to Tc-99m, under gaseous anesthesia, using either the commercially available AeroNeb Go® or the investigational HYDRA device, placed in-line with the inspiratory limb of a breathing circuit. Lambs were scanned in a single-photon emission computed tomography (SPECT/CT) scanner in the supine position during the administration procedure. Measurements and Main Results: Both the HYDRA and AeroNeb Go® produced palivizumab aerosols in the 1–5 µm range with similar median (geometric standard deviation and range) aerosol droplet diameters for the HYDRA device (1.84 ± 1.40 μm, range = 0.54–5.41μm) and the AeroNeb Go® (3.07 ± 1.56 μm, range = 0.86–10 μm). Aerosolized palivizumab was delivered to the lungs at 88.79–94.13% of the total aerosolized amount for all lambs, with a small proportion localized to either the trachea or stomach. No difference between devices were found. Pulmonary deposition ranged from 6.57 to 9.25% of the total dose of palivizumab loaded in the devices, mostly in the central right lung. Conclusions: Aerosolized palivizumab deposition patterns were similar in all lambs, suggesting a promising approach in the control of severe RSV lung infections

Free Radical Generation from High-Frequency Electromechanical Dissociation of Pure Water

We reveal a unique mechanism by which pure water can be dissociated to form free radicals without requiring catalysts, electrolytes, or electrode contact by means of high-frequency nanometer-amplitude electromechanical surface vibrations in the form of surface acoustic waves (SAWs) generated on a piezoelectric substrate. The physical undulations associated with these mechanical waves, in concert with the evanescent electric field arising from the piezoelectric coupling, constitute half-wavelength "nanoelectrochemical cells" in which liquid is trapped within the SAW potential minima with vertical dimensions defined by the wave amplitude (∼10 nm), thereby forming highly confined polarized regions with intense electric field strengths that enable the breakdown of water. The ions and free radicals that are generated rapidly electromigrate under the high field intensity in addition to being convectively transported away from the cells by the bulk liquid recirculation generated by the acoustic excitation, thereby overcoming mass transport limitations that lead to ion recombination.A.R.R., N.C., and L.Y.Y. acknowledge funding support from the Australian Research Council through Discovery Project (DP180102110); Future Fellowship (FT140100834); and Linkage, Infrastructure, Equipment & Facilities (LE170100023) grant

Which patients are not included in the English Cancer Waiting Times monitoring dataset, 2009-2013? Implications for use of the data in research.

BACKGROUND: Cancer waiting time targets are routinely monitored in England, but the Cancer Waiting Times monitoring dataset (CWT) does not include all eligible patients, introducing scope for bias. METHODS: Data from adults diagnosed in England (2009-2013) with colorectal, lung, or ovarian cancer were linked from CWT to cancer registry, mortality, and Hospital Episode Statistics data. We present demographic characteristics and net survival for patients who were and were not included in CWT. RESULTS: A CWT record was found for 82% of colorectal, 76% of lung, and 77% of ovarian cancer patients. Patients not recorded in CWT were more likely to be in the youngest or oldest age groups, have more comorbidities, have been diagnosed through emergency presentation, have late or missing stage, and have much poorer survival. CONCLUSIONS: Researchers and policy-makers should be aware of the limitations in the completeness and representativeness of CWT, and draw conclusions with appropriate caution

Приклади завдань для позакласної роботи з інформатики у початковій школі

У статті коротко описана методика проведення позакласної роботи з інформатики у початковій школі