Microsqueeze force sensor useful as contact-free profilorneter and viscometer

We present a sensor for measuring viscous friction forces in liquids proximal to a substrate. The sensor is implemented as a mechanical oscillator that is damped by the liquid squeezed in the gap between the sensor head and the substrate. Force versus distance curves were recorded ranging from 100 pm down to a few microns and are in agreement with the expected power law for the damping curve. The viscosity ratios of different liquids were measured with the sensor and are in accordance with values in the literature. Moreover, the topography of an immersed substrate was recorded with micrometer lateral and vertical resolution by scanning the sensor in constant height mode above the surface. (C) 2005 American institute of Physics.