Microfabrication of SiN membrane nanosieve using anisotropic reactive ion etching (ARIE) with an Ar/CF4 gas flow.

We have designed, fabricated, and characterized a low-stressed silicon nitride (SiN) membrane nanosieve (100 microm x 100 microm) using an anisotropic reactive ion etching (ARIE) combining with gas mixture, thus maintaining compatibility with the complementary metal-oxide semiconductor integrated circuit (CMOS IC) processes. The holes pattern of this nanosieve membrane was precisely controlled under 30 nm diameter by the electron beam writing. By employing mainly anisotropic reactive ion etching plus diffusion to the depth direction, the etch holes size was controlled to be the same with patterns on the e-beam resist (ER). This nanosieve membrane has proper mechanical strength withstanding up to one bar of transmembrane pressure. And it can endure harsh treatments such as high temperature up to 800 degrees C. In addition, it is inert to a number of strong chemicals including the piranha (H2SO4 + H2O2) solution, highly-concentrated potassium hydroxide (KOH), hydrogen fluoride (HF), hydrogen chloride (HCI), and nitric acid (HNO3).

A simple and smart telemedicine device for developing regions: a pocket-sized colorimetric reader.

We have proposed a novel mobile healthcare platform, combining a pocket-sized colorimetric reader (13.5 × 6.5 × 2.5 cm(3)) and commercially available 10-parameter urinalysis paper strips (glucose, protein, glucose, bilirubin, urobilinogen, ketones, nitrite, pH, specific gravity, erythrocytes, and leukocytes), capable of sending data with a smart phone. The reader includes a novel colorimetric multi-detection module, which consists of three-chromatic light-emitting diodes, silicon photodiodes and a novel poly(methylmethacrylate) (PMMA) optical splitter. We employed data reading methods using conversions of the signal data (red, blue, and green) to the hue (H) color map or the Y model data, and used a curve-fitting method for the quantification. The reader is battery-powered, inexpensive, light-weight, and very speedy in analysis. And, it was applied to detection of a thousand of human urine samples and demonstrated reliable quantification of urinary glucose and protein. The features can be used by unskilled people on-site to transfer the analyzed data to experts off-site.

A surface acoustic wave-based immunosensing device using a nanocrystalline ZnO film on Si.

The novelty of this study resides in the fabrication of a bio-sensing device, based on the surface acoustic wave (SAW) on a nanocrystalline ZnO film. The ZnO film was deposited using an rf magnetron sputtering at room temperature on silicon. The deposited films showed the c-axis-oriented crystallite with grain size of approximately 40 nm. The immunosensing device was fabricated using photolithographic protocols on the film. As a model biomolecular recognition and immunosensing, biospecific interaction between a 6-(2,4-dinitrophenyl)aminohexanoic acid (DNP) antigen and its antibody was employed, demonstrating the shifts of resonant frequencies on SAW immunosensing device. The device exhibited a linearity as a function of the antibody concentration in the range of 20-20,000 ng/ml.

Nanocrystalline ZnO film layer on silicon and its application to surface acoustic wave-based streaming.

A surface acoustic wave (SAW) device consisting of 1-6 microm-thick ZnO thin films deposited on Si wafer was designed, fabricated, and characterized in this study. Photolithographic protocols for interdigitated transducers (IDTs) and surface modification using fluoroalkylsilane are employed with the aim of droplet-based microfluidic actuations in bio-microsystems. A ZnO thin film was grown on a 4' silicon wafer with c-axis orientation, an average roughness of 11.6 nm, and a small grain size of 20 nm. It was found that the resonant frequencies (Rayleigh and Sezawa modes) of SAW devices move to a lower frequency range as the thickness of the ZnO thin films increases. Through the silane surface modification, a hydrophobic surface with a contact angle of 114 degrees was obtained. Finally, liquid streaming by acoustic wave was demonstrated by observing the actuation of SiO2 microparticles in a microfluidic drop.