Integrated Dual Grating Polymer Microbeams for Bio-chemical Sensing in Liquid Environment

A polymer microbeam array integrated with dual gratings for interferometric measurement was developed for biochemical sensing in liquid environment. An Au-coated polyimide microbeam structure suspending a centered plate was designed to realize out-plane translational motion. The microbeam array chip was fabricated on a glass substrate based on surface micromachining process. Two adjacent metal gratings corresponding to a microbeam were patterned inside and outside of a groove with the depth of 55 nm to form a phase shift of pi/2 to extend the displacement measurement range. The interferometric intensities from the two gratings were detected using a CCD image measurement setup and the displacement of a microbeam was obtained by alternately using intensity signals from the two corresponded gratings. The preliminary experimental results in ethanol show that the detection method with the polymer microbeam chip is available in liquid environment. And antibody-antigen binding detection was also carried out with a rabbit IgG immobilized chip in 100 mu g/ml goat anti-rabbit IgG solution.