Abstract: A closed loop microfluidic device that has at least one microchannel formed in a body and a pump in fluid connection with the microchannel. The pump is actuated by an external motive force to push and pull fluid through the microchannel. A number of chambers are formed in fluid connection with the microchannel to store reagents. The reagents are moved through the microchannel by the pump. A number of active zones are also formed in the microchannel. Various reactions and diagnostics are performed at the active zone. A sample is introduced to the microchannel through a sealable input port. The microchannel forms a closed loop with all necessary reagents and diagnostics contained within the closed loop microfluidic device. The sample is processed and analysed completely within the closed loop microchannel.