cules ▁that ▁can ▁bind ▁more ▁per flu or in ated ▁termin ations ▁to ▁the ▁surface ▁can ▁results ▁in ▁lower ing ▁the ▁surface ▁energy ▁( high ▁water ▁contact ▁angle ). ▁ ▁Me as uring ▁methods ▁ ▁The ▁static ▁sess ile ▁drop ▁method ▁ ▁The ▁sess ile ▁drop ▁contact ▁angle ▁is ▁measured ▁by ▁a ▁contact ▁angle ▁g oni ometer ▁using ▁an ▁optical ▁sub system ▁to ▁capture ▁the ▁profile ▁of ▁a ▁pure ▁liquid ▁on ▁a ▁solid ▁substr ate . ▁The ▁angle ▁formed ▁between ▁the ▁liquid – sol id ▁interface ▁and ▁the ▁liquid – v apor ▁interface ▁is ▁the ▁contact ▁angle . ▁Old er ▁systems ▁used ▁a ▁mic ros cope ▁optical ▁system ▁with ▁a ▁back ▁light . ▁Current - gener ation ▁systems ▁employ ▁high ▁resolution ▁cam eras ▁and ▁software ▁to ▁capture ▁and ▁analyze ▁the ▁contact ▁angle . ▁Ang les ▁measured ▁in ▁such ▁a ▁way ▁are ▁often ▁quite ▁close ▁to ▁adv ancing ▁contact ▁angles . ▁Equ ilib rium ▁contact ▁angles ▁can ▁be ▁obtained ▁through ▁the ▁application ▁of ▁well ▁defined ▁v ibr ations . ▁ ▁The ▁pendant ▁drop ▁method ▁Me as uring ▁contact ▁angles ▁for ▁pendant ▁dro ps ▁is ▁much ▁more ▁complicated ▁than ▁for ▁sess ile ▁dro ps ▁due ▁to ▁the ▁inher ent ▁un stable ▁nature ▁of ▁invert ed ▁dro ps . ▁This ▁complexity ▁is ▁further ▁ampl ified ▁when ▁one ▁attempts ▁to ▁incl ine ▁the ▁surface . ▁Ex perimental ▁appar atus ▁to ▁measure ▁pendant ▁drop ▁contact ▁angles ▁on ▁incl ined ▁substr ates ▁has ▁been ▁developed ▁recently . ▁This ▁method ▁allows ▁for ▁the ▁de position ▁of ▁multiple ▁micro dro ps