Effect of gravity on the macroscopic advancing contact angle of sessile drops

A series of experiments were conducted in a reduced gravity (near-free-fall) environment (g approximate to 0) and on ground (g = 1) to study the effect of gravity on the advancing contact angles of sessile drops. The reduced net acceleration force was produced by parabolic flights. The ground experiments were conducted for various three-phase contact-line advancing rates whereas the reduced gravity experiments were conducted for only one advancing rate due to the short duration of reduced gravity. The experimental results show that for water sessile drops on Teflon-coated silicon wafers, the advancing contact angle in the reduced gravity environment is less than that of the advancing contact angle in 1g (126 degrees) by about 5 degrees for the same three-phase contact line advancing rates.