| Summary: |
Blood is an extraordinary fluid from the rheological point of view. Among its characteristics, one should mention shear thinning and elasticity and scale dependent rheology. Shear thinning and elasticity damp shear stress and velocity oscillations. Scale dependent
rheology permits that the blood adapts to a network in which the largest scale is 1000 times larger than the smallest one. Blood has to respect several simultaneous optimization requirements in order to assure oxygen distribution, low shear stresses and to avoid
clogging and settling. This is possible due to red blood cells (RBCs) unusual characteristics. RBCs are flexible disk shaped oxygen carriers with a high surface to volume ratio. They have fine-tuned density, aggregation and disaggregation characteristics according to shear rate, and can migrate to the bulk flow and change shape in small vessels.
While blood is an elegant solution to a very specific problem, solved through evolutionary adaptions that took millions of years, similar problems exist in biomedical industry and research. The transport of small particles in hierarchical networks is presently in
biomedical topics: tissues engineering, chemical and biological reactors and drug delivery. Additionally, one may wish to fine-tune the rheology of some fluids for mechanical engineering or research purposes. An example is the development of blood analogues for
in vitro hemodynamics.
In this project, we adopt the view that useful solutions can be obtained mimicking solutions already developed by natural selection. A large set of biomimetic solutions for engineering problems has been created in this spirit (e.g. [1]). The purpose of the present
project is to explore the range of possible blood like fluids and the methods to control their characteristics. The result, we expect, will be a collection of biomimetic solutions to engineering problems. Additionally, we expect to develop a deeper understanding of
how rheological properties em  |
Summary
Blood is an extraordinary fluid from the rheological point of view. Among its characteristics, one should mention shear thinning and elasticity and scale dependent rheology. Shear thinning and elasticity damp shear stress and velocity oscillations. Scale dependent
rheology permits that the blood adapts to a network in which the largest scale is 1000 times larger than the smallest one. Blood has to respect several simultaneous optimization requirements in order to assure oxygen distribution, low shear stresses and to avoid
clogging and settling. This is possible due to red blood cells (RBCs) unusual characteristics. RBCs are flexible disk shaped oxygen carriers with a high surface to volume ratio. They have fine-tuned density, aggregation and disaggregation characteristics according to shear rate, and can migrate to the bulk flow and change shape in small vessels.
While blood is an elegant solution to a very specific problem, solved through evolutionary adaptions that took millions of years, similar problems exist in biomedical industry and research. The transport of small particles in hierarchical networks is presently in
biomedical topics: tissues engineering, chemical and biological reactors and drug delivery. Additionally, one may wish to fine-tune the rheology of some fluids for mechanical engineering or research purposes. An example is the development of blood analogues for
in vitro hemodynamics.
In this project, we adopt the view that useful solutions can be obtained mimicking solutions already developed by natural selection. A large set of biomimetic solutions for engineering problems has been created in this spirit (e.g. [1]). The purpose of the present
project is to explore the range of possible blood like fluids and the methods to control their characteristics. The result, we expect, will be a collection of biomimetic solutions to engineering problems. Additionally, we expect to develop a deeper understanding of
how rheological properties emerge from the fluid components and interactions.
Particulate fluids will be developed by associating solvents, particles and additives. The additives can have two roles: modify the rheological properties of the base solvent and modify adhesion between particles. The range of properties to explore includes:
solvent rheology, aggregation additives and particles shape, dimensions and elasticity. Other properties may be also of interest, in order to adapt the fluid for particular cases, such as particle density and refractive index.
A crucial aspect of the project is the production of microparticles with tunable properties. Here, we take advantage of the expertise of the research team on microfluidics [PP2-PP4, 2, 3] and multiphase flows [PP1,PP5]. Two methods of producing microparticles are
pursued: particle formation from droplets generated in microfluidics, and particles produced by photolithography. The former method has already been tested in our lab with success (see http://paginas.fe.up.pt/~jmiranda/fluidDesigner/index.html). The
latter one is very flexible, allowing the production of disk shaped particles, but it requires experimental development. The fluids obtained in the project will be characterized in our lab rheometers and in experimental microfluidic devices.
The project will be focused in two applications: development of blood analogue fluids for hemodynamics research and development of particles for carrying solutes in vessel networks. The first application aims to solve present research limitations of blood
analogues in hemodynamics in vitro research. No analogue exists that can simultaneously have the rheological properties of blood, at all scales, and the adequate refractive index for experimental studies. The second application will take advantage of the particles
fabricated to develop solute carriers for drug delivery and similar functions. We expect that these fluids and particles may find new applications the fields of tissues engineering and biotechnology, as oxygen and drug carriers. The technology developed will be
available for commercial exploitation and could be the basis for a service of designer fluids on demand.
The research team has a large experience in fluid mechanics [PP1,PP3,PP5], multiphase flow [PP1,PP5], mass transport [2] and hemodynamics studies [PP3, 3, 4]. Additionally, the team has know how in computational fluid dynamics. Particle methods, adequate to simulate particulate flows, are currently a subject of a PhD thesis being developed in the research group (FCT research grant SFRH/BD/91192/2012). The numerical technique developed will be used as a tool to improve and speed up the design of new particles in this project. |