Design,Fabrication And Interferometric Measurement Method Using Dual-grating Of Microbeams For Surface Stress Sensing

Biochemical detection technology is widely required in many areas, such asdisease diagnosis, food safety, environmental monitoring, national defense andanti-terrorism. The microbeam based array sensors play important roles in thedevelopment of the biochemical assay for miniaturization, integration, high throughput,multi-target and high sensitivity detection. In this dissertation, with a final goal ofrealizing high throughput, high sensitivity, and low detection limit biochemicaldetection, an interferometric displacement measurement method of array based onintegrated dual gratings and CCD detection, which can be used for the detection ofbiochemical binding surface stress, is studied. It provides a way to the development ofbiochemical array detection. Based on these, research has been done as follows,Firstly, the principle of interferometric displacement detection based on integrateddual gratings was introduced. The output light intensity of integrated grating withdifferent parameters was simulated using commercial software based on the vectordiffraction theory and cosine fitted. The deviation of the fitting results from thesimulating ones was analyzed. Then, the influence of the distance between the reflectingsurface and grating and the duty cycle of the grating on the standard deviation, intensitycontrast and light intensity peak was studied, followed by the design of integrateddual-grating. Finally, a calculation process for the interferometric displacementmeasurement based on integrated dual gratings were presented and validated bysimulation.The mechanical model of parallel-moving microbeam structures for surface stresssensing was studied. The material selection and the microbeam structure design werecarried out by considering the sensitivity and the mechanical thermal noise. Structuralparameters of the support beam and the length of the sensitive layer on its surface wereoptimized using the finite element simulation. The detection sensitivity of themicrobeams and a compensation method for biochemical detection were analyzed.The fabrication process of sensing microbeams on a transparent substrate wasinvestigated. The process of lithography and lift-off to pattern the metallic gratings onglass shallow grooves was achieved using a metal reflective assistant layer. Polymer surface micromachining process using aluminum as a sacrificial layer was designed,process experiments and thrice fabrication processes were carried out, and finallyparallel-moving microbeam was fabricated.A CCD based detection system was established. The system noises were analyzed,and the results shows that the main noise come from the intensity drift and randomnoise of the expanded laser beam, the complex imaging optical path made the systemnoise increase, and the noise slightly increased in liquid environment. Experiments onfabricated chips were carried out. The measured displacement of aluminum beams in airand polyimide ones in liquid was650nm and800nm, respectively. A preliminaryimmune detection response experiment with goat anti-rabbit IgG and rabbit IgG using apolyimide sensing chip was carried out.