Abstract: The invention relates to a micro valve for use in a biosensor, a micro fluidic device, use of such a device, and a micro fluidic element. Biosensors are used for detection of molecules and/or ions, such as protein, drug, DNA, RNA, hormone, glucose, insulin, enzyme, fungus, bacterium, etc., in a biological sample. The sensor can be used for diagnostic application, but for instance also drugs, either therapeutic or abuse, may be detected in for instance blood, urine and saliva.