A cast-in-place and lithographically shaped mobile, monolithic polymer element for fluid flow control in microfluidic devices and method of manufacture. The lever plate has a fitting hole into which a shaft part of the adjustable vane is fitted formed at a position close to one end of an elongated plate main body thereof and an engaging protrusion to be engaged with the drive ring formed at the other end thereof. When the sequentially stripping-off type adhesive tape is placed on the holding member, it needs only that the adhesive tape is rotated for a circle, the tearing areas on one side of the adhesive tape pieces can be brought out, then the user can tear the adhesive tape pieces in either of two ways until the whole roll of adhesive tape is all used. The assembly is also suitable for modulation methods that use a modulation with phase and amplitude variation. The complementary datum features on both shield and shield retention stage enable accurate and repeatable positioning of the sample in the apparatus for sample processing and reprocessing.