This study presents a polyimide (PI) self-assembly technique for developing a 3-D surface-micromachined structure. The effects of geometric factors and curing temperatures of PI elastic joints on the lifting angles of such 3-D microstructures are investigated. Under the optimized curing condition (380°C), a maximum 74-deg lifting angle of 5.2×10−11 kg-weight polysilicon microplate is achieved utilizing a large thermal shrinkage force of a single PI joint. Before severe cross-linkage occurred (curing at 390 to 400°C), the lifting angle of the thermally actuated 3-D microstructure is nearly in direct proportion to the length/width-thickness ratio of the PI joint (with linearity of 95.5%) and the difference between curing and room temperatures (with linearity of 92.3 to 97%). The PI-based self-assembly process is very suitable for mass production due to its high yield of fabrication (80 to 91.6%) and high compatibility with the present IC and MEMS manufacturing processes.
To identify the extreme low concentration of alpha-fetoprotein (AFP) antigen in human serum for early detection of hepatocellular carcinoma, we aim to develop a high-sensitivity and low-cost AFP biosensor using quartz crystal microbalance (QCM) and cystamine self-assembly monolayer (SAM) technologies. In this study, the surface topographies of concentrations (0.1 and 1.0 mg/mL) of AFP antibody with and without 1.25% glutaraldehyde cross-linking layer will be analyzed by an atomic force microscope system to investigate the effects of the glutaraldehyde layer on the sensing characteristics of the QCM-based AFP biosensor. According to our experimental results, the mass sensitivity was improved almost doubly (from 0.07 to 0.146 Hz mL mg−1) as the glutaraldehyde layer was added between the 20-mM cystamine SAM and the low-concentration (0.1 mg/mL) AFP antibody. Either with or without the glutaraldehyde layer, higher mass sensitivity (0.163 to 0.335 Hz mL mg−1) was obtained as the AFP antibody concentration increased to 1.0 mg/mL. However, a large AFP antibody requirement will increase fabrication cost and limit disposable application. We also demonstrated that high sensing linearities (95.67 to 99.6%) of the QCM-AFP biosensors can be achieved without being obviously affected by the glutaraldehyde layer and AFP antibody concentration.
Printed electronics have attracted increasing attentions in recent years due to its flexible format, easy process and potentially
low cost features. Achieving good performance organic Schottky diode as the key component of a rectifier for printed RFID
applications became a critical task. The electrical performances of an organic Schottky diode electrical can be improved by
inserting an intermediate layer between the semiconductor and electrode surfaces. This interface plays an important role in
improving rectification ratio and lifetime of a polymer diode. In this work, a 13.56MHz rectifier based on a polymer
Schottky diode will be demonstrated and a wireless energy transmission built on flexible substrates will be proposed.