Biomedical subjects

L E Helseth

Publications and source records attributed to L E Helseth.

21 records · Page 2Linked to original sources

PubMed2003

Particle interactions near the contact line in liquid drops.

Micrometer-sized particles distributed in a drop of water are drawn toward the contact line upon evaporation, where they arrange themselves into a crystal structure. Here we report experiments with paramagnetic particles, which make it possible to measure the particle interactions by tuning an external magnetic field. By aligning the magnetic dipoles, we are also able to redistribute the particles back into the bulk of the droplet. This method allows us to assemble and disassemble colloidal crystals simply by applying a magnetic field.

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PubMed2003

Adsorption and diffusion in a one-dimensional potential well.

We investigate the adsorption and diffusion of colloidal particles at an interface containing a one-dimensional potential well. It is observed how the adsorption kinetics onto the wall is altered with time, and one observes the formation of a particle chain. We find that the time it takes for a bead to penetrate into the chain depends strongly on the particle density, and beyond a critical value this time diverges. We also study diffusion within the well, and find that at low particle densities the short time behavior is governed by normal Fickian diffusion.

Journal Article↗

PubMed2003

Paramagnetic beads surfing on domain walls.

Paramagnetic beads electrostatically stabilized in aqueous solution are attracted toward domain walls in magnetic films. The position above the domain wall can be destabilized by realigning the beads magnetic moment with an external magnetic field. The destabilization may result in a steady state dissipative mode, where the beads surf on the slope of the moving domain wall. The technique could be an alternative route to probe electrostatic and hydrodynamic interactions between particles and interfaces, and could also serve as a model system for studying motion in a one-dimensional potential.

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