▁based ▁on ▁the ▁fluid ▁behavior ▁in ▁the ▁device ▁micro ch annels . ▁These ▁devices ▁take ▁advantage ▁of ▁the ▁fluid ▁behavior ▁and ▁the ▁small ▁forces ▁within ▁this ▁mic rom eter ▁order ▁domain ▁to ▁manipulate ▁cells ▁in ▁solution . ▁E ff ort s ▁have ▁been ▁made ▁to ▁develop ▁methods ▁of ▁sorting ▁rare ▁cells ▁from ▁a ▁solution ▁that ▁can ▁be ▁used ▁in ▁point - of - care ▁applications , ▁low ▁sample ▁volumes , ▁and ▁do ▁not ▁require ▁expensive ▁equipment ▁in ▁order ▁to ▁sort ▁cells . ▁The ▁isol ation ▁of ▁rare ▁cells ▁from ▁a ▁blood ▁solution ▁such ▁as ▁cancer , ▁tum or , ▁or ▁stem ▁cells ▁still ▁remains ▁to ▁be ▁a ▁critical ▁technical ▁challenge ▁due ▁to ▁other ▁methods ▁requiring ▁either ▁expensive ▁equipment ▁that ▁is ▁limited ▁to ▁lab ▁environments ▁or ▁requiring ▁a ▁large ▁sample ▁volume ▁in ▁order ▁to ▁develop ▁a ▁hydro ▁dynamically ▁focused ▁stream ▁of ▁single ▁cells . ▁This ▁type ▁of ▁sorting ▁has ▁also ▁been ▁recognized ▁to ▁have ▁a ▁more ▁gentle ▁approach ▁to ▁cells ▁due ▁to ▁the ▁small ▁forces ▁needed ▁to ▁sort ▁them ▁in ▁these ▁domains ▁which ▁leads ▁to ▁better ▁cell ▁vi ability ▁after ▁sorting . ▁The ▁different ▁methods ▁can ▁be ▁broken ▁down ▁into ▁active ▁and ▁pass ive : ▁ ▁Active ▁ ▁Active ▁cell ▁sorting ▁involves ▁the ▁detection ▁of ▁targets ▁cells ▁through ▁a ▁mic ros cope ▁or ▁camera ▁followed ▁by ▁the ▁automatic ▁or ▁manual ▁activation ▁of ▁an ▁actu ation ▁method ▁to ▁alter ▁the ▁fluid ▁flow ▁in ▁the ▁micro fl uid ic ▁channels . ▁Some ▁techniques ▁util ize ▁flu ores cent ▁tag ging ▁similar ▁to ▁what ▁is ▁used ▁in