0000000000023596
AUTHOR
Markus Preuss
showing 6 related works from this author
Measuring the Contact Angle of Individual Colloidal Particles.
1998
The aim of this study was to measure the contact angles of individual colloidal spheres ( solidus in circle 4.4 µm) and compare it to contact angles obtained on similarly prepared planar surfaces. For this purpose the particles were attached to atomic force microscope cantilevers. Then the force between the particle in aqueous medium and an air bubble was measured versus the distance. From the resulting force curves we obtained contact angles and detachment forces of single particles. Contact angles of gold coated silica particles were adjusted between 20 degrees and 100 degrees by self-assembling monolayers from different mixtures of undecanethiols and omega-hydroxy undecanethiols from sol…
Microsphere tensiometry to measure advancing and receding contact angles on individual particles
1999
In this paper, a method to measure the advancing and receding contact angles on individual colloidal spheres is described. For this purpose, the microspheres were attached to atomic force microscope cantilevers. Then the distance to which the microsphere jumps into its equilibrium position at the air-liquid interface of a drop or an air bubble was measured. From these distances the contact angles were calculated. To test the method, experiments were done with silanized silica spheres (4.1 μm in diameter). From the experiments with drops, an advancing contact angle of 101 ± 4° was determined. A receding contact angle of 101 ± 2° was calculated from the jump-in distance into a bubble. Both ex…
Adhesion and Friction Forces between Spherical Micrometer-Sized Particles
1999
An experimental setup, based on the principles of atomic force microscopy (AFM), was used to measure directly the adhesion and rolling-friction forces between individual silica microspheres of radii between 0.5 and 2.5 \ensuremath{\mu}m. It showed that the linear dependence of the pull-off force on the particle radius is still valid for micron-sized particles. Rolling-friction forces between silica microspheres were measured for the first time by combining AFM methods and optical microscopy: They are $\ensuremath{\sim}100$ times lower than the corresponding adhesion forces.
Direct measurement of forces between particles and bubbles
1999
One of the elementary stages of the flotation process is the formation of an aggregate between the particle and a bubble. This aggregate formation is governed by hydrodynamic, capillary and interparticle forces. During the last four years, techniques have been developed to measure directly the force between a colloidal particle and a bubble. These techniques are closely related to the development of atomic force microscopy. Advantages and possibilities, as well as limits and drawbacks are described.
Preliminary results on the electrostatic double-layer force between two surfaces with high surface potentials
1998
Abstract The aim of this study is to measure interaction forces between surfaces with high electric potentials in aqueous electrolyte solutions. Therefore the force between a gold sample and a gold sphere attached to the end of an atomic force microscope cantilever was measured. Gold sample and sphere were electrically connected and served as the working electrode. A potential was applied via a platinized platinum electrode. Experimental results are compared to forces approximated with the Poisson-Boltzmann theory.
Direct Measurement of Particle−Bubble Interactions in Aqueous Electrolyte: Dependence on Surfactant
1998
The aim of this study was to determine the influence of surfactant on the particle−bubble interaction. Therefore we constructed an experimental setup with which the interaction between colloidal pa...