Low-temperature plasma treatment for hydrophobicity improvement of silk

The SF6 plasma parameters were measured at the center of the chamber. The electron temperature was about 3-5 eV and the ion density was 1.0-3.5×1010 cm−3. The optical emission spectroscopy results show the mixture of fluorine ion inside the plasma. The hydrophobicity improvement of silk was achieved. The treated samples reach the limit of the absorption times at 180 min and increase the contact angle to 130-140°. These results show a significant increase in the hydrophobic property compared with the untreated sample. The optimum operating conditions were at an RF power of around 50 W and a pressure of 3-5 mTorr.