Sofie Högberg

Respiratory Deposition of Fibers in the Non-Inertial Regime—Development and Application of a Semi-Analytical Model

A semi-analytical model describing the motion of fibrous particles ranging from nano- to micro scale was developed, and some important differences in respiratory tract transport and deposition between fibrous particles of various sizes and shapes were elucidated. The aim of this work was to gain information regarding health risks associated with inhalation exposure to small fibers such as carbon nanotubes. The model, however, is general in the sense that it can be applied to arbitrary flows and geometries at small fiber Stokes and Reynolds numbers. Deposition due to gravitational settling, Brownian motion and interception was considered, and results were presented for steady, laminar, fully developed parabolic flow in straight airways. Regarding particle size, our model shows that decrease in particle size leads to reduced efficiency of sedimentation but increased intensity of Brownian diffusion, as expected. We studied the effects due to particle shape alone by varying the aspect ratios and diameters of the microfibers simultaneously, such that the effect of particle mass does not come into play. Our model suggests that deposition both due to gravitational settling and Brownian diffusion decreases with increased fiber aspect ratio. Regarding the combined effect of fiber size and shape, our results suggest that for particles with elongated shape the probability of reaching the vulnerable gas-exchange region in the deep lung is highest for particles with diameters in the size range 10–100 nm and lengths of several micrometers. Note that the popular multi-walled carbon nanotubes fall into this size-range.

Motion of dispersed carbon nanotubes during impregnation of fabrics

Abstract Interest is growing in the development of hierarchical composites, in which nanoscale particles are used alongside the traditional microscale reinforcing fibres. To produce high quality multiscale materials, knowledge of mechanisms governing nanofibre distribution and orientation is crucial. In this work, analysis and numerical simulations are used to model the motion of dispersed carbon nanotubes during impregnation of dual scale fabrics in composites manufacturing. Results suggest that nanofibre displacement and orientation is mainly deterministic on mesoscale, while typically random on microscale. The randomising Brownian torque may still influence the motion and trigger the fibre to make 180° rotations in the former, however, when acting together with the fluid shear. Fibre deposition may lead to a total blockage of the flow within the microchannels, whereas only minor deposition is expected in the mesochannels.

Time-Dependent Deposition of Micro- and Nanofibers in Straight Model Airways

In this paper, we increase the understanding of the influence of the breathing pattern on the fate of inhaled non-spherical micro and nanoparticles and examine the accuracy of replacing the cyclic ...

Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway

A model for the motion and deposition of oblate and prolate spheroids in the nano- and microscale was developed. The aim was to mimic the environment of the human lung, but the model is general and ...