Flow-based　microfluidic　biochips　(FBMBs)　have　attracted　much　attention　over　the　past　decade.　On　such　a　micrometer-scale　platform,　various　biochemical　applications,　also　called　bioas-says,　can　be　processed　concurrently　and　automatically.　To　improve　execution　efficiency　and　reduce　fabrication　cost,　a　distributed　channel-storage　architecture　(DCSA)　can　be　implemented　on　this　platform,　where　fluid　samples　can　be　cached　temporarily　in　flow　channels　close　to　components.　Although　DCSA　can　improve　the　execution　efficiency　of　FBMBs　significantly,　it　requires　a　careful　arrangement　of　fluid　samples　to　enable　the　channels　to　fulfill　the　dual　functions　of　transportation　and　caching.　In　this　paper,　we　formulate　the　first　flow-layer　physical　design　problem　considering　DCSA,　and　propose　a　top-down　synthesis　algorithm　to　generate　efficient　solutions　considering　execution　efficiency,　washing,　and　resource　usage　simultaneously.　Experimental　results　demonstrate　that　the　proposed　algorithm　leads　to　a　shorter　execution　time,　less　flow-channel　length,　and　a　higher　efficiency　of　on-chip　resource　utilization　for　biochemical　applications　compared　with　a　direct　approach　to　incorporate　distributed　storage　into　existing　frameworks.　©　2019　EDAA.