Research / 2020 / Article / Fig 2

Research Article

The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity

Figure 2

Apparent contact angles versus gravity. (a) AFM images of the sample solid surfaces and their section analyses. The analyses show that the surfaces are very smooth, with roughness less than 1 nm. (b) The contact angle on solid surfaces at different gravities. The contact angles show the same tendency to decrease with increasing gravity. The contact angle hysteresis was smaller than 3°, except for the cases of ethylene glycol and glycerol on PDMS9K. (c) Comparison of (the difference in contract angles at 1 G and 8 G) and (the average contact angle hysteresis). Independent -test was applied, , , , , , , and , for water on DMDCS, water on PDMS9K, ethylene glycol on PDMS2K, glycerol on DMDCS, glycerol on PDMS2K, and glycerol on PDMS9K, respectively. Five out of the nine solid-liquid contact systems showed significant larger than , three showed comparable results. The experimental results confirmed that the decrease in the contact angle upon increasing gravity is caused by gravity, not only by the contact angle hysteresis.