| Summary: | The centrifugal technique was employed to investigate the influence of substrate materials (aluminium, acrylic and plywood), particle size and humidity on particle-surface adhesion force. Substrate materials loaded with monodispersed polymer microspheres (with mean diameter of 2 µm, 10 µm and 20 µm) were rotated up to a maximum rotation speed of 6,000 rpm in a micro-centrifuge Particles were detached by rolling off the surface upon experiencing a centrifugal force.
Plywood substrate was the most adhesive to the aerosol particles with only 4% of particles detached, followed by aluminium and acrylic substrate being the least adhesive to the aerosol particles with 12.7% detached from the surface.
The particle size and the relative humidity had direct proportionality relationship the adhesion force. The 2 µm particles had the smallest ratio of F_det/F_adh equal to 0.25%, indicating that the detachment force experienced by the particles was not enough to overcome the adhesion force. The meniscus formed in between the particle and substrate at high humidity levels created another form of adhesion force. This adhesion force caused by the surface tension of water molecules was calculated to be 9.1 µN which was relatively large compared to the Van der Waals adhesion force of 135 nN. As a result, the force needed to detach the particles has to be much stronger than the adhesion force.
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