Using　the　optical　feedback　interferometry　(OFI)　technique,　we　demonstrated　a　miniaturized　and　compact　sensor　system　based　on　a　dedicated　optical　source　for　flowmetry　at　the　micro-scale.　In　the　system,　polymer　microlenses　were　integrated　directly　on　a　VCSEL　(vertical-cavity　surface-emitting　laser)　chip　and　the　microfluidic　channel　chip　surface　using　polymer-based　micro-fabrication　technologies.　In　particular,　at　a　post-process　stage,　we　integrated　a　collimation　lens　on　a　VCSEL　chip　of　small　dimensions　(200　mu　m　x　200　mu　m　x　150　mu　m).　This　process　was　enabled　by　the　soft-printing　of　dry　thick　resist　films　and　through　direct　laser　writing　technology.　We　performed　flow　rate　measurements　using　this　new　compact　system,　with　a　conventional　bulk　glass　lens　configuration　for　system　performance　evaluation.　A　maximum　33　dB　signal-to-noise　ratio　was　achieved　from　this　novel　ultra-compact　system.　To　our　knowledge,　this　is　the　highest　signal　level　achieved　by　existing　OFI　based　flowmetry　sensors.