Abstract
This study try using UV-LIGA technology, coupled with UV lithography and micro electroforming technique, to hot-emboss a high resolution and high aspect-ratio microstructure for a planar Mach-Zehnder Interferometer (MZI). The polymer MZI chip will be used as a portable, high sensitivity biochemical sensor. In cooperated with a real-time demolding mechanism, the experimental results showed that the MZI microstructure can be hot embossed in PMMA material with a minimum feature size of 1μm and an aspect ratio of 6 after processes optimization of the Taguchi methods. A composite material of WGC was then spin-coated in the molded PMMA microstructure as the core of the waveguide. The refractive index of the WGC material was modulated providing single mode transmission of the NIR light source. Optical measurement results showed that transmission efficiency of the molded MZI is good (~5 dB), and the deviation of the transmission intensity could be as low within 4%. The measurement results also indicate that the molded MZI chip can detect a concentration change of 10^-9g/ml of the sodium chloride solution, which corresponding to a refractive index change of 10^-11. In addition, the antibody-conjugated gold nanoparticles were tried to enhance the sensitivity of the MZI sensor since the refractive index difference is quite large between gold and bimolecular. By using the gold nanoparticles, the measurement results showed that the detection sensitivity of the SU-8 MZI chip can be improved from 10^-12g/ml to 10^-14g/ml. Once the molded MZI chip coupled with nanoparticle amplification, the low-cost, portable and high-sensitivity biosensing scheme will benefit the detection, prevention and curing of decease.