FIGURE 4.

(A) Variations in contact angle of CO₂-brine-quartz with the surfactin production, and (B) the digital images of sessile drops of CO₂ in contact to the quartz disk before and after the surfactin production. Note: The dotted lines indicate the contact angle values from previous literature; the value for gaseous CO₂ (1) is from Kim and Santamarina (2014) and the values for liquid and supercritical CO₂ (2, 3) are from Sarmadivaleh et al. (2015). The droplet images in B correspond to the dotted circles in A.