Abstract
Microelectromechanical Systems and micromachining is the mainstream of industrial development. Use of traditional machining to make high aspect ratio structure has disadvantages like tool wear, longer processing time and cannot be mass produced. Sapphire is hard and brittle material and it is very difficult to use the traditional mechanical processing methods to process it. In this study, we used electroplated Ni as a mask during sapphire inductively coupled plasma (ICP) etching with Cl2/BCl3/Ar gas mixtures. A gas mixture of Cl2/BCl3/Ar was used to etch the sapphire with process variables including BCl3 flow ratio and bias power. An X-ray sapphire resonator cavity with a depth of 95 μm, a crystal width of ~ 30 μm, a crystal gap of ~115 μm, and a vertical sidewall profile of 89.5 ° was obtained by etching for 540 minutes. The resonant spectrum of the x-ray resonant cavity of the sapphire was successfully observed. In addition, a novel package technology has been developed for miniaturized AlGaN/GaN field-effect transistor biosensors by Nd:YVO4 and CO2 laser drilling. We investigated the effect of laser drilling parameters on the PMMA substrate, double side tape and hydrophilic film, which are required for PMMA mold, PMMA channel and capillary channel. A hydrophilic film and double side tapes were patterned using CO2 laser drilling to generate a channel and an outlet pattern. The stack of double side tapes and hydrophilic film were then stuck together to form the capillary microchannel. The PMMA substrate was also patterned using CO2 laser drilling to generate a PMMA mold and PMMA channel. The miniaturized AlGaN/GaN high electron mobility transistors (HEMTs) were embedded in an epoxy substrate and connected with metal electrodes. The epoxy substrates were drilled in the shape of a micro-SD card with two holes by Nd:YVO4 laser. The epoxy substrate was passivated by photoresist to make openings on the transistor and gate electrode regions, followed by bonding a microfluidic channel made of PMMA and capillary channel. Finally, C-reactive protein (CRP) aptamer was then immobilized on the AlGaN/GaN HEMT inside the capillary channel. CRP was essfully detected in standard buffer solution and human serum using the disposable biosensor chip and the portable readout device. The result shows that this portable system is promising in personal healthcare in the future.