Design of an innovative polymerase chain reaction device based on buoyancy driven flow

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Polymerase Chain Reaction (PCR) plays a central role in the field of molecular biology. The miniaturization of PCR systems is promising as it potentially minimizes costly reagent consumption and time required for analysis. In PCR microdevices a sample solution is usually handled by external pumps. An alternative solution relies on temperature-induced density difference in the presence of a body force to induce buoyancy driven flow. This alternative method is easy to be used and does not require expensive setup, but, to date, the thermo-fluid-dynamic field in the micro-channels still needs to be optimized. The present study focuses on the design of micro-channels, having innovative and optimized shapes to obtain proper fluid actuation and DNA sample amplification within buoyancy driven flow PCR devices. A parametric study is carried out by means of computational thermal fluid dynamic modeling: several channel geometry configurations were compared in terms of time required for analysis, temperature distribution and priming volume. The advantages and disadvantages of such configurations are discussed

Computational and experimental investigation of mixing in microchannels

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Mixing is a key process for the successful of all chemical or biochemical reactions, so effective micromixers represent essential components for micro total analysis systems (μTAS) or lab-on-a-chip. In the present study a combined computational and experimental approach was adopted to evaluate how the efficiency of a Y-mixer can be enhanced by modifying its downstream geometry. Three different geometries were studied and compared: Y-straight channel, Y-sine channel and Y-wrinkled wall channel. For each of them the influence of perfusing flow rates and channel cross section aspect ratio was investigated. Physical prototypes were built using a simple technique based on a xerographic process, and their mixing performance was experimentally evaluated. Computational models of the designed micromixers were generated: the Navier-Stokes equations for an incompressible Newtonian fluid and the advection-diffusion equation were solved with an uncoupled approach by means of the finite volume method. The computational and experimental results were critically compared, revealing Y-wrinkled wall mixer as the best performer among those considered and suggesting criteria of possible improvements and optimization

Numerical simulation of a deformable cell in microchannels

The main goal of this work is to numerically investigate the behavior of a cell flowing in a microfluidic system. In particular, we want to model flow-induced deformations of an isolated cell to quantitatively evaluate the cell response when subjected to a representative range of flow rates in a realistic geometry, with specific interest in the case of cell trapping. This research will help optimize operating conditions as well as the design of cell manipulation/culture micro-devices, so as to guarantee cell viability and ultimately improve high-throughput performance

Design of an air-flow microchamber for microparticles detec

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.A novel device, able to funnel a suspension of micrometric particles in air into a microchamber equipped with a capacitive sensor, has been designed for the detection and characterization of particulate matter (PM) in air. Numerical simulations have been performed to predict the trajectory of the microparticles through the PDMS microchamber where the sensor is located. The feasibility of detecting single PM10 particles has been demonstrated by our experiments, where sequences of single industrial talc particles (average diameter of 8 μm) have been detected and counted by a capacitive sensor. Our results indicate that radical miniaturization of air quality monitors is possible and, therefore, pervasive monitoring of air pollution will be soon feasible

µ-Particle tracking velocimetry and computational fluid dynamics study of cell seeding within a 3D porous scaffold

Cell seeding of 3D scaffolds is a critical step in tissue engineering since the final tissue properties are related to the initial cell distribution and density within the scaffold unit. Perfusion systems can transport cells to the scaffold however; the fact that cells flow inside the scaffold pores does not guarantee cell deposition onto the scaffold substrate and cell attachment. The aim of this study was to investigate how fluid flow conditions modulate cell motion and deposition during perfusion. For such a purpose, a multiphase-based computational fluid dynamics (CFD) model was developed in conjunction with particle tracking velocimetry experiments (PTV) which for the first time were applied to observe cell seeding inside a 3D scaffold. CFD and PTV results showed the strong effect of gravity for lower flow rates leading to cell sedimentation and poor transport of cells to the scaffold. Higher flow rates help overcome the effect of gravity so more cells travelling inside the scaffold were found. Nonetheless, fluid flow drags cells along the fluid streamlines without intercepting the scaffold substrate. As a consequence, if cells do not deposit into the scaffold substrate, cell adhesion cannot occur. Therefore, cell-scaffold interception should be promoted and the present computational model which predicts the effect of gravity and fluid drag on cells trajectories could serve to optimise bioreactors and enhance cell seeding efficiency

Una Experiencia de Prevención del Acoso Entre Pares en Niños Escolarizados

En el presente trabajo se presenta la experiencia de capacitación con docentes y directivos en relación a la prevención del acoso entre pares (presencial y virtual) en niños de Escuelas Municipales de la ciudad de Córdoba. Se adopta el enfoque de educación en habilidades para la vida como estrategia para la construcción de una convivencia saludable en el ámbito escolar, en consonancia con los lineamientos formulados por la Organización Panamericana de la Salud (2001), la cual recomienda que los programas escolares integren al currículo los conocimientos, valores y habilidades necesarias para el desarrollo de estilos de vida saludable. Sensibilizar y concienciar a los docentes sobre la necesidad de intervenir y desarrollar actuaciones para fortalecer habilidades interpersonales y de la comunicación como forma de reducción y prevención del acoso entre pares. La experiencia se abordó desde la metodología de Investigación Acción Participativa. Se desarrollaron 4 encuentros con modalidad de jornada taller de 4 horas cada uno. Participaron 45 docentes y 60 directivos. Los participantes discriminan conductas de riesgos en relación al acoso entre pares de aquellas acciones que favorecerían la salud y convivencia; destacaron la importancia de favorecer la comunicación; proponen el trabajo cooperativo, fomentando la solidaridad; reconocen la problemática del acoso entre pares y su incidencia en edades tempranas. El trabajo demuestra que el docente, en la medida que fortalece en los alumnos diferentes habilidades interpersonales y de la comunicación, potencia la construcción de vínculos solidarios orientados a la convivencia saludable a nivel escolar, familiar y comunitario

Salivary cortisol measurement in normal-weight, obese and anorexic women: comparison with plasma cortisol

OBJECTIVE: To compare salivary, plasma and urinary free cortisol (UFC) measurements in patients with anorexia nervosa, in whom an overdrive of the hypothalamic-pituitary-adrenal (HPA) axis is well established but information on salivary cortisol is lacking, in viscerally obese patients in whom subtle abnormalities of cortisol secretion and metabolism are postulated, and in normal-weight healthy women. PARTICIPANTS AND EXPERIMENTAL DESIGN: Measurement of salivary cortisol offers a convenient way to assess the concentrations of free, biologically active cortisol in plasma in different physiopathological settings. Forty-seven drug-free, newly diagnosed women with active restrictive anorexia nervosa, 30 restrictive anorexic women undergoing chronic psychopharmacological treatment, 47 women with mild-to-moderate visceral obesity, 103 women with severe central obesity and 63 normal-weight healthy women entered the study. Salivary and blood samples were collected at 0800 h, 1700 h and 2400 h, together with three consecutive 24-h urine specimens for UFC determination. In controls and patients with anorexia nervosa (n=83), salivary and plasma cortisol were also measured after a 1-mg overnight dexamethasone suppression test (DST). In patients with anorexia nervosa, mood was rated by the Hamilton scale for anxiety and depression. RESULTS: Untreated patients with anorexia nervosa showed increased plasma and salivary cortisol and UFC concentrations (all P<0.001 compared with controls), and decreased cortisol suppression after DST in plasma and saliva (P<0.0001 and P<0.005 respectively compared with controls). These alterations were less pronounced, although still statistically significant, in treated patients with anorexia nervosa. Salivary cortisol was highly correlated with paired plasma cortisol in the whole population and after splitting the participants by group (P<0.0001). However, for plasma cortisol values greater than 500 nmol/l (the corticosteroid-binding globulin saturation point), this parallelism was lost. Taking plasma cortisol as a reference, the level of agreement for post-dexamethasone salivary and plasma cortisol was 58.9% among suppressors and 77.8% among non-suppressors (chi2 test: P<0.01). Decreased 0800 h/2400 h cortisol ratios were observed in plasma and saliva in drug-free patients with anorexia nervosa (P<0.005 and P<0.05 respectively compared with controls), and in saliva in severely obese patients (P<0.05 compared with controls). Depression and anxiety scores were unrelated to cortisol concentrations in any compartment. CONCLUSIONS: Salivary cortisol measurement is a valuable and convenient alternative to plasma cortisol measurement. It enables demonstration of the overdrive of the HPA axis in anorexia nervosa and subtle perturbations of the cortisol diurnal rhythm in women with visceral obesity. With the establishment of more specific and widely acceptable cut-off values for dynamic testing, measurement of salivary cortisol could largely replace plasma cortisol measurement