. ▁The ▁shapes ▁of ▁three - dimensional ▁sess ile ▁and ▁pendant ▁dro ps ▁have ▁been ▁successfully ▁predicted ▁using ▁this ▁energy ▁minim isation ▁method . ▁ ▁Typ ical ▁contact ▁angles ▁ ▁Contact ▁angles ▁are ▁extremely ▁sensitive ▁to ▁cont am ination ; ▁values ▁reprodu cible ▁to ▁better ▁than ▁a ▁few ▁degrees ▁are ▁generally ▁only ▁obtained ▁under ▁labor atory ▁conditions ▁with ▁pur ified ▁liqu ids ▁and ▁very ▁clean ▁solid ▁surfaces . ▁If ▁the ▁liquid ▁mole cules ▁are ▁strongly ▁attract ed ▁to ▁the ▁solid ▁mole cules ▁then ▁the ▁liquid ▁drop ▁will ▁completely ▁spread ▁out ▁on ▁the ▁solid ▁surface , ▁corresponding ▁to ▁a ▁contact ▁angle ▁of ▁ 0 ° . ▁This ▁is ▁often ▁the ▁case ▁for ▁water ▁on ▁bare ▁met all ic ▁or ▁cer am ic ▁surfaces , ▁although ▁the ▁presence ▁of ▁an ▁ox ide ▁layer ▁or ▁cont amin ants ▁on ▁the ▁solid ▁surface ▁can ▁significantly ▁increase ▁the ▁contact ▁angle . ▁Gener ally , ▁if ▁the ▁water ▁contact ▁angle ▁is ▁smaller ▁than ▁ 9 0 ° , ▁the ▁solid ▁surface ▁is ▁considered ▁hydro ph il ic ▁and ▁if ▁the ▁water ▁contact ▁angle ▁is ▁larger ▁than ▁ 9 0 ° , ▁the ▁solid ▁surface ▁is ▁considered ▁hydro ph ob ic . ▁Many ▁polym ers ▁exhib it ▁hydro ph ob ic ▁surfaces . ▁High ly ▁hydro ph ob ic ▁surfaces ▁made ▁of ▁low ▁surface ▁energy ▁( e . g . ▁flu or in ated ) ▁materials ▁may ▁have ▁water ▁contact ▁angles ▁as ▁high ▁as ▁ ≈   1 2 0 ° . ▁Some ▁materials ▁with ▁highly ▁rough ▁surfaces ▁may ▁have