This　paper　presents　a　novel　approach　for　automatic,　rapid　and　efficient　micro-droplet　mixing　on　＇open-surface＇　droplet-based　microfluidics　system　via　magnetic　actuation.　A　two-step　micro-fabrication　process　was　employed　to　decorate　the　magnetically　functionalized　polydimethylsiloxane　(PDMS)　membrane　with　micro-pillar　arrays　(MPA)　to　reduce　the　adhesion　on　resident　droplets.　Droplet　manipulation　relies　on　the　localized　deformation　of　the　elastic　membrane　under　external　magnetic　fields,　thus　relieving　the　additives　of　magnetic　components　to　the　droplets　that　is　commonly　required　in　conventional　magnetism-based　actuation.　Via　integration　with　peripheral　computer-based　regulator,　swift　droplet　mixing　is　realized　via　controlling　the　coalescent　droplets　back　and　forth　to　generate　internal　fluid　circulations　for　enhanced　mass　transfer　within　the　droplet.　The　comparison　of　mixing　performance　between　the　coalesce-and-stop　and　back-and-forth　mode　was　systematically　performed,　which　verifies　that　the　back-and-forth　actuation　of　the　droplets　can　obviously　improve　the　mixing　efficiency,　and　typically　a　higher　driving　frequency　on　the　droplet　renders　a　shorter　mixing　duration.　With　driving　frequency　of　2.5　cycles/s,　the　mixing　homogeneity　can　reach　80%　within　0.6　s　and　reach　90%　within　1.5　s.　Also,　it　has　been　experimentally　demonstrated　that　the　proposed　system　can　accelerate　the　dilution　under　various　volume　ratios,　including　1:2,　1:5,　and　1:10.　Finally,　we　demonstrated　that　the　platform　can　be　used　to　dynamically　manipulate　the　droplets,　allowing　the　de-pinning　effect　for　molecular　concentrating　and　obvious　detection　sensitivity　enhancement　in　terms　of　Surface-Enhanced　Raman　Scattering　(SERS).　Owing　to　the　superiorities　including　programmable　efficient　mixing　and　parallel　scalability,　the　study　herein　offers　insights　for　exploiting　cost-effective　and　versatile　microfluidics　platform　for　future　application　in　biological　analysis,　chemical　micro-reactions,　and　trace　molecule　detections.