▁training ▁to ▁apply ▁and ▁because ▁they ▁are ▁not ▁as ▁ha z ard ous ▁as ▁other ▁need les , ▁making ▁the ▁administration ▁of ▁dru gs ▁to ▁patients ▁sa fer ▁and ▁less ▁pain ful ▁while ▁also ▁avoid ing ▁some ▁of ▁the ▁draw back s ▁of ▁using ▁other ▁forms ▁of ▁drug ▁delivery , ▁such ▁as ▁risk ▁of ▁in fection , ▁production ▁of ▁ha z ard ous ▁waste , ▁or ▁cost . ▁ ▁Background ▁▁ ▁Mic r one ed les ▁were ▁first ▁mentioned ▁in ▁a ▁ 1 9 9 8 ▁paper ▁on ▁trans der mal ▁drug ▁delivery ▁demonstr ating ▁that ▁mic r one ed les ▁could ▁pen et rate ▁human ▁skin . ▁Sub sequ ent ▁research ▁into ▁mic r one ed le ▁drug ▁delivery ▁has ▁expl ored ▁the ▁medical ▁and ▁cos met ic ▁applications ▁of ▁this ▁technology ▁through ▁its ▁design . ▁This ▁early ▁paper ▁sought ▁to ▁explore ▁the ▁possibility ▁of ▁using ▁mic r one ed les ▁in ▁the ▁future ▁for ▁v acc ination . ▁Since ▁then ▁research ers ▁have ▁studied ▁mic r one ed le ▁delivery ▁of ▁ins ul in , ▁v acc ines , ▁anti - infl amm ator ies , ▁and ▁other ▁ph arma ce ut ical s . ▁In ▁der mat ology , ▁mic r one ed les ▁are ▁used ▁for ▁sc arring ▁treatment ▁with ▁skin ▁roll ers . ▁▁▁▁▁ ▁The ▁major ▁goal ▁of ▁any ▁mic r one ed le ▁design ▁is ▁to ▁pen et rate ▁the ▁out most ▁layer ▁of ▁the ▁skin ▁the ▁str atum ▁cor neum ▁( 1 0 - 1 5