To　fully　utilize　the　dynamic　reconfigurability　of　digital　microfluidic　biochips,　most　of　electrodes　would　be　shared　by　different　droplets.　Thus,　contaminations　caused　by　liquid　residues　among　droplets　are　inevitable　which　lead　to　lethal　errors　in　bioassays.　To　remove　the　contaminations,　washing　operations　are　introduced　as　an　essential　step　to　ensure　the　correctness　of　bioassay.　However,　existing　works　have　oversimplified　assumptions　on　the　washing　droplets　behavior　and　constraints　which　cannot　clean　all　contaminations　with　erroneous　outcomes.　Moreover,　straightforward　integration　of　washing　operations　with　droplet　routing　may　increase　the　execution　time　of　a　bioassay　which　is　not　feasible　for　timing-critical　bioassay.　To　effectively　remove　contaminations　and　minimize　the　execution　time　of　a　bioassay,　this　article　proposes　a　unified　contamination-aware　routing　method,　which　addresses　the　above　issues　simultaneously.　Firstly,　we　present　a　top-down　scheme　to　generate　candidates　of　routing　paths,　then　construct　a　shortest-path　model　to　select　desirable　routing　solution　for　all　subproblems.　With　a　decision　diagram　of　droplets,　we　further　propose　an　integer　linear　programming　(ILP)　formulation　to　compact　the　execution　time.　Finally,　contamination　removal　by　washing　droplets　with　realistic　washing　capacity　is　considered　for　all　subproblems.　Tested　on　real-life　benchmarks,　our　proposed　method　can　significantly　reduce　72%　contamination　spots　and　save　11%　execution　time.