Where Lext :	maximum extraction length of the microchannel
γ :	surface tension between the two phases
θcontact :	contact angle between the two phases
w :	half-width of microchannel
h :	height of microchannel
ΔPoutlet :	difference between the hydrodynamic pressures in the outlets
Qaq and Qorg :	flow rates of the aqueous and organic phases, respectively
$\overline{R_{\mathit{\text{aq}}-\mathit{\text{ext}}}}\overline{R_{\mathit{\text{org}}-\mathit{\text{ext}}}}$:	hydrodynamic resistance of the microchannel per unit length in the extraction zone of the aqueous and organic phases, respectively
Ψ :	maximum extraction efficiency
Dext :	diffusivity of the extracting species
Uext :	linear velocity of the phase in which the extracting species is diffusing towards the interface
$k=\sqrt{\frac{D_{\mathit{\text{ext}}}}{U_{\mathit{\text{ext}}}}}\text{and}{\lambda }_n=\frac{n\pi }{2w}$.