Biological　assays　around　＂lab-on-a-chip　(LoC)＂　are　required　in　multiple　concentration　(or　dilution)　factors,　satisfying　specific　sample　concentrations.　Unfortunately,　most　of　them　suffer　from　non-locality　and　are　non-protectable,　requiring　a　large　footprint　and　high　purchase　cost.　A　digital　geometric　technique　can　generate　arbitrary　gradient　profiles　for　digital　microfluidic　biochips　(DMFBs).　A　next-　generation　DMFB　has　been　proposed　based　on　the　microelectrode-dot-array　(MEDA)　architectures　are　shown　to　produce　and　disperse　droplets　by　channel　dispensing　and　lamination　mixing.　Prior　work　in　this　area　must　address　the　problem　of　reactant　and　waste　minimization　and　concurrent　sample　preparation　for　multiple　target　concentrations.　This　paper　proposes　the　first　splitting-droplet　sharing　algorithm　for　reactant　and　waste　minimization　of　multiple　target　concentrations　on　MEDAs.　The　proposed　algorithm　not　only　minimizes　the　consumption　of　reagents　but　also　reduces　the　number　of　waste　droplets　by　preparing　the　target　concentrations　concurrently.　Experimental　results　on　a　sequence　of　exponential　gradients　are　presented　in　support　of　the　proposed　method　and　demonstrate　its　effectiveness　and　efficiency.　Compared　to　prior　work,　the　proposed　algorithm　can　achieve　up　to　a　24.8%　reduction　in　sample　usage　and　reach　an　average　of　50%　reduction　in　waste　droplets.