Pmma Waveguide-based Music Just Wave Device Characterization

Chemical sensor development is being increasingly driven by the need for real time analyses. Nowadays, the use of surface acoustic devices as chemical sensors is well known. However, as a common acoustic mode, Rayleigh wave can't provide enough sensitivity to satisfy several special applications, for example, detection of chemical war agents in battlefield environments. To resolve the problem, the design and fabrication of Love wave resonator devices have been investigated in the dissertation. The chief results and conclusions obtained are as follows:(1)According to SAW theory, the Surface skimming bulk waves(SSBWs) resonator and delay line devices are designed and fabricated. For comparison, both of them have the same pattern of interdigital transducers(IDTs). Compared with delay line, the resonator has the lower insertion loss(resonator: 38.8dB; delay line: 47dB) and higher Q value(resonator: 594; delay line: 230), which enhances the frequency stability of devices.(2)The spin coating technology is modified: the solutions with low concentration is chosen to obtain the layer with a smooth surface; the steps are formed on the edges of substrate to raise the thickness of layer obtained during the spin coating process. In experiments, the PMMA layers with thickness of 0.8?3.3μm are obtained. The thickness of layers depends on the spin speed and the concentration of solution. The roughness of layers depends on the lasting time of the low speed and the difference between the low speed and high speed. The modified spin coating technology also shows nice repeatability.(3) The Love wave devices are obtained by spin coating PMMA guiding layer on the surface of SSBW devices. The properties of devices, such as, frequency, insertion loss, Q value and mass sensitivity are studied as a function of the guiding layer thickness. And then the properties of resonator and delay line devices are also compared. Due to the enhancement of the electromechanical coupling and the efficient guiding of acoustic energy in the guiding layer, insertion loss initially decreases with increasing guiding layer thickness and reaches the minimum at 1.3μm. At the greater thickness, decrease in coupling and the acoustic absorption of guiding layer results in the increase of insertion loss. But the variation of Q value following the increase of thickness is contrary to that of insertion loss. Compared with delay line, the Love wave resonator devices can further suppress insertion loss and enhance Q value, but shows the same mass sensitivity. The mass sensitivity up to 1179cm2 g?1 is got at the thickness of 2.25μm.