▁which ▁a ▁user ▁must ▁press ▁the ▁home ▁button ▁to ▁have ▁the ▁home ▁screen ▁appear , ▁however ▁this ▁can ▁be ▁changed ▁in ▁the ▁iOS ▁settings ▁to ▁where ▁users ▁can ▁just ▁rest ▁their ▁finger ▁on ▁the ▁sensor ▁to ▁un lock ▁the ▁user ' s ▁device ▁and ▁go ▁directly ▁to ▁the ▁home ▁screen , ▁similar ▁to ▁previous ▁versions ▁of ▁iOS . ▁So le ly ▁placing ▁a ▁finger ▁on ▁the ▁sensor ▁will ▁only ▁un lock ▁the ▁iPhone ▁unless ▁said ▁setting ▁is ▁enabled , ▁and ▁no ▁notifications ▁are ▁currently ▁being ▁displayed ▁on ▁the ▁lock ▁screen . ▁ ▁Gener ations ▁ ▁Hard ware ▁ ▁Touch ▁ID ▁is ▁built ▁into ▁the ▁home ▁button , ▁which ▁is ▁built ▁of ▁las er - cut ▁sa pp hire ▁cry stal , ▁and ▁does ▁not ▁scratch ▁easily ▁( scr atch ing ▁would ▁prevent ▁Touch ▁ID ▁from ▁working ). ▁It ▁features ▁a ▁st ain less ▁steel ▁detection ▁ring ▁to ▁detect ▁the ▁user ' s ▁finger ▁without ▁pressing ▁it . ▁There ▁is ▁no ▁longer ▁a ▁rounded ▁square ▁icon ▁in ▁the ▁home ▁button , ▁nor ▁is ▁it ▁con ca ve . ▁ ▁The ▁sensor ▁uses ▁capac itive ▁touch ▁to ▁detect ▁the ▁user ' s ▁finger print . ▁The ▁sensor ▁has ▁a ▁thick ness ▁of ▁ 1 7 0   µ m , ▁with ▁ 5 0 0 ▁pixels ▁per ▁in ch ▁resolution . ▁The ▁user ' s ▁finger ▁can ▁be ▁orient ed ▁in ▁any ▁direction ▁and ▁it ▁will ▁still ▁be ▁read . ▁Apple ▁says ▁it ▁can ▁read ▁sub - ep id erm al ▁skin ▁layers , ▁and