Laura Campo-Deaño

Bio: Laura Campo-Deaño is an academic researcher from Faculdade de Engenharia da Universidade do Porto. The author has contributed to research in topics: Rheology & Viscoelasticity. The author has an hindex of 14, co-authored 37 publications receiving 790 citations. Previous affiliations of Laura Campo-Deaño include University of Vigo & University of Porto.

The slow retraction method (SRM) for the determination of ultra-short relaxation times in capillary breakup extensional rheometry experiments

Abstract: We monitor the capillary thinning and breakup of low viscous liquid filaments with high speed imaging to determine the relaxation time of dilute polymer solutions in extension The induction of filament thinning by a slow extension of a liquid bridge beyond the static stability limit enables one to create axially symmetric thinning profiles with minimized inertial oscillations from acceleration of the liquid The minimized disturbance of the capillary thinning process by this slow retraction method (SRM) allows the observation and quantitative fitting of the visco-capillary and inertio-visco-capillary balance as well as the potential flow regime for a series of Newtonian liquids covering a viscosity range from 350 to 27 mPa s For dilute solutions of polyethylene oxide in water the SRM allows the reliable determination of relaxation times in extension of as low as 240 μs A lower limit for the polymer concentration c l o w below which an elasto-capillary balance cannot be observed is introduced, based on the finite extensibility limit L2 of the polymer chain

Viscoelasticity of blood and viscoelastic blood analogues for use in polydymethylsiloxane in vitro models of the circulatory system

Abstract: The non-Newtonian properties of blood are of great importance since they are closely related with incident cardiovascular diseases. A good understanding of the hemodynamics through the main vessels of the human circulatory system is thus fundamental in the detection and especially in the treatment of these diseases. Very often such studies take place in vitro for convenience and better flow control and these generally require blood analogue solutions that not only adequately mimic the viscoelastic properties of blood but also minimize undesirable optical distortions arising from vessel curvature that could interfere in flow visualizations or particle image velocimetry measurements. In this work, we present the viscoelastic moduli of whole human blood obtained by means of passive microrheology experiments. These results and existing shear and extensional rheological data for whole human blood in the literature enabled us to develop solutions with rheological behavior analogous to real whole blood and with a refractive index suited for PDMS (polydymethylsiloxane) micro- and milli-channels. In addition, these blood analogues can be modified in order to obtain a larger range of refractive indices from 1.38 to 1.43 to match the refractive index of several materials other than PDMS.

Microfluidic systems for the analysis of viscoelastic fluid flow phenomena in porous media

Abstract: In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better insight about the flow characteristics of viscoelastic fluids flowing through a packed bed. For these purposes, flow visualizations and pressure drop measurements are conducted with Newtonian and viscoelastic fluids. The 1-D microfluidic analogues of porous medium consisted of microchannels with a sequence of contractions/expansions disposed in symmetric and asymmetric arrangements. The real porous medium is in reality, a complex combination of the two arrangements of particles simulated with the microchannels, which can be considered as limiting ideal configurations. The results show that both configurations are able to mimic well the pressure drop variation with flow rate for Newtonian fluids. However, due to the intrinsic differences in the deformation rate profiles associated with each microgeometry, the symmetric configuration is more suitable for studying the flow of viscoelastic fluids at low De values, while the asymmetric configuration provides better results at high De values. In this way, both microgeometries seem to be complementary and could be interesting tools to obtain a better insight about the flow of viscoelastic fluids through a porous medium. Such model systems could be very interesting to use in polymer-flood processes for enhanced oil recovery, for instance, as a tool for selecting the most suitable viscoelastic fluid to be used in a specific formation. The selection of the fluid properties of a detergent for cleaning oil contaminated soil, sand, and in general, any porous material, is another possible application.

Flow of low viscosity Boger fluids through a microfluidic hyperbolic contraction

Abstract: In this work we focus on the development of low viscosity Boger fluids and assess their elasticity analyzing the flow through a microfluidic hyperbolic contraction. Rheological tests in shear and extensional flows were carried out in order to evaluate the effect of the addition of a salt (NaCl) to dilute aqueous solutions of polyacrylamide at 400, 250, 125 and 50 ppm (w/w). The rheological data showed that when 1% (w/w) of NaCl was added, a significant decrease of the shear viscosity curve was observed, and a nearly constant shear viscosity was found for a wide range of shear rates, indicating Boger fluid behavior. The relaxation times, measured using a capillary break-up extensional rheometer (CaBER), decreased for lower polymer concentrations, and with the addition of NaCl. Visualizations of these Boger fluids flowing through a planar microfluidic geometry containing a hyperbolic contraction, which promotes a nearly uniform extension rate at the centerline of the geometry, was important to corroborate their degree of elasticity. Additionally, the quantification of the vortex growth upstream of the hyperbolic contraction was used with good accuracy and reproducibility to assess the relaxation time for the less concentrated Boger fluids, for which CaBER measurements are difficult to perform.

Particle manipulations in non-Newtonian microfluidics: A review.

Abstract: Microfluidic devices have been widely used since 1990s for diverse manipulations of particles (a general term of beads, cells, vesicles, drops, etc.) in a variety of applications. Compared to the active manipulation via an externally imposed force field, the passive manipulation of particles exploits the flow-induced intrinsic lift and/or drag to control particle motion with several advantages. Along this direction, inertial microfluidics has received tremendous interest in the past decade due to its capability to handle a large volume of samples at a high throughput. This inertial lift-based approach in Newtonian fluids, however, becomes ineffective and even fails for small particles and/or at low flow rates. Recent studies have demonstrated the potential of elastic lift in non-Newtonian fluids for manipulating particles with a much smaller size and over a much wider range of flow rates. The aim of this article is to provide an overview of the various passive manipulations, including focusing, separation, washing and stretching, of particles that have thus far been demonstrated in non-Newtonian microfluidics.

The stab resistance of fabrics impregnated with shear thickening fluids including various particle size of additives

Abstract: Shear thickening fluid (STF) treated high performance fabrics have attracted much attention in the applications of body protection. In order to improve the contribution of STF treatments, we designed multi-phase STFs and investigated the stab resistance of fabrics impregnated with these novel fluids. Silica and polyethylene glycol (PEG) based STFs were synthesized with various particle size of silicon carbide (SiC) additives to constitute the multi-phase suspension systems. The influence of the additive particles on the thickening behavior of the STFs was analyzed via rheological testing. The stab resistance of the fabrics was investigated in a drop tower against spike and knife threats and therefore, the role of the STFs was discussed in detail. According to this study, multi-phase STFs realized further improvement in the stab resistance of fabrics with respect to single-phase STFs.