A　microchannel　with　serial　converging–diverging　geometries,　inspired　by　porous　structures　of　rock,　was　designed　to　enhance　the　cross-interfacial　mass　transfer　of　two-phase　flow　at　a　high　phase　injection　ratio　up　to　200:1.　It　was　experimentally　demonstrated　that　the　design　enhanced　mass　transfer　coefficient　by　approximately　four　times　compared　to　classic　microchannel　design.　The　superior　performance　of　the　microchannel　was　attributed　to　the　retention　of　dispersed　fluid　before　the　converging　geometry　due　to　the　capillary　pressure　barrier　that　resulted　in　velocity　contrast　between　the　two　fluids　and　reduced　the　effective　mass-transfer　distance　in　continuous　phase.　Additionally,　the　deformation　and　dispersal　of　droplets　at　the　diverging　geometry　further　increased　the　interfacial　area.　The　flow　patterns　in　this　geometry　were　experimentally　identified.　The　serial　converging–diverging　design　can　be　used　for　high　phase　ratio　extraction　applications.　©　2022