We describe two new measurement techniques for studying the wetting behavior of a liquid on a surface. First, we measure the contact angle of a droplet, by measuring the capacitance between a conducting droplet and a subsurface counter electrode. The estimated error in the measured contact angle is 2% for contact angles in the range between 60 degrees and 120 degrees. In the second measurement technique, we detect the current as a function of time, which provides information about the dynamics of a droplet wetting the substrate. The time-integrated current is related to the base area of the droplet. Consequently, we can derive the radial velocity of the three-phase line of the droplet. The time resolution of the measurement technique is limited by the charging time of the initial capacitance, in our case approximately 0.5 ms. (C) 1999 American Institute of Physics. [S0034-6748(99)03409-7].
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