A microfluidic device a micromachined freestanding member adapted to sense one or more properties of a fluid flowing through the freestanding member. The freestanding member is supported by a substrate and spaced apart and separated from the substrate to enable the freestanding member to move relative to the substrate under the influence of a vibration-inducing element. Movement of the freestanding member relative to the substrate is then sensed by a sensing element. The freestanding member has an inlet, an outlet, an internal passage that fluidically couples the inlet and outlet, and a wall that defines and separates first and second passage portions of the internal passage that are arranged in fluidic series so that a fluid flowing through the internal passage flows through the first and second passage portions in opposite directions.