Electrochemical engineering of hollow nanoarchitectures: pulse/step anodization (Si, Al, Ti) and their applications.

Hollow nanoarchitectured materials with straight channels play a crucial role in the fields of renewable energy, environment and biotechnology due to their one-dimensional morphology and extraordinary properties. The current challenge is the difficulty on tailoring hollow nanoarchitectures with well-controlled morphology at a relatively low cost. As a conventional technique, electrochemistry exhibits its unique advantage on machining nanostructures. In this review, we present the progress of electrochemistry as a valuable tool in construction of novel hollow nanoarchitectures through pulse/step anodization, such as surface pre-texturing, modulated, branched and multilayered pore architectures, and free-standing membranes. Basic principles for electrochemical engineering of mono- or multi-ordered nanostructures as well as free-standing membranes are extracted from specific examples (i.e. porous silicon, aluminum and titanium oxide). The potential of such nanoarchitectures are further demonstrated for the applications of photovoltaics, water splitting, organic degradation, nanostructure templates, biosensors and drug release. The electrochemical techniques provide a powerful approach to produce nanostructures with morphological complexity, which could have far-reaching implications in the design of future nanoscale systems.

Recent developments in optical detection technologies in lab-on-a-chip devices for biosensing applications.

The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches for the detection technologies in lab-on-a-chip devices: (a) study of the compatibility of conventional instrumentation with microfluidic structures, and (b) integration of innovative sensors contained within the microfluidic system. Despite the recent advances in electrochemical and mechanical based sensors, their drawbacks pose important challenges to their application in disposable microfluidic devices. Instead, optical detection remains an attractive solution for lab-on-a-chip devices, because of the ubiquity of the optical methods in the laboratory. Besides, robust and cost-effective devices for use in the field can be realized by integrating proper optical detection technologies on chips. This review examines the recent developments in detection technologies applied to microfluidic biosensors, especially addressing several optical methods, including fluorescence, chemiluminescence, absorbance and surface plasmon resonance.

Fabrication and assembly of MEMS accelerometer-based heart monitoring device with simplified, one step placement.

An accelerometer-based heart monitoring system has been developed for real-time evaluation of heart wall movement. In this paper, assembly and fabrication of an improved device is presented along with system characterization and test data from an animal experiment. The new device is smaller and has simplified the implantation procedure compared to earlier prototypes. Leakage current recordings were well below those set by the corresponding standards.

Integrated optical microfluidic biosensor using a polycarbazole photodetector for point-of-care detection of hormonal compounds.

A picogram-sensitive optical microfluidic biosensor using an integrated polycarbazole photodiode is developed. The photodetector is mainly composed of the blend heterojunction of poly [N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) and the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the hole transport layer. Analyte detection is accomplished via a chemiluminescent immunoassay performed in a poly(dimethylsiloxane)-gold-glass hybrid microchip, on which antibodies were immobilized and chemiluminescent horseradish peroxidase-luminol-peroxide reactions were generated. Enhanced sensor response to the chemiluminescent light is achieved by optimizing the thickness of PCDTBT: PC70BM and PEDOT:PSS. Using the optimized polycarbazole photodiode for detecting the human thyroid-stimulating hormone as the model target, the integrated biosensor demonstrates an excellent linearity in the range of 0.03 to 10 ng/ml with an analytical sensitivity of 68 pg/ml. The sensor response shows high specificity and reproducibility. Hormone detection in clinical samples is further demonstrated and compared with a commercial enzyme-linked immunosorbent assay. The integrated device reported here has potential to detect other hormonal compounds or protein targets. Moreover, the presented concept enables the development of miniaturized, low-cost but highly sensitive optical microfluidic biosensors based on integrated polymer photodetectors with high potential for point-of-care diagnostics.

Integration of Carbon Nanotubes in Microsystems: Local Growth and Electrical Properties of Contacts.

Carbon nanotubes (CNTs) have been directly grown onto a silicon microsystem by a local synthesis method. This method has potential for wafer-level complimentary metal-oxide-semiconductor (CMOS) transistor-compatible integration of CNTs into more complex Si microsystems; enabling, e.g., gas sensors at low cost. In this work, we demonstrate that the characteristics of CNTs grown on specific locations can be changed by tuning the synthesis conditions. We also investigate the role of the contact between CNTs and the Si microsystem; observing a large influence on the electrical characteristics of our devices. Different contact modes can render either an ohmic or Schottky-like rectifying characteristics.

Local Synthesis of Carbon Nanotubes in Silicon Microsystems: The Effect of Temperature Distribution on Growth Structure.

Local synthesis and direct integration of carbon nanotubes (CNTs) into microsystems is a promising method for producing CNT-based devices in a single step, low-cost, and wafer-level, CMOS/MEMS-compatible process. In this report, the structure of the locally grown CNTs are studied by transmission imaging in scanning electron microscopy-S(T)EM. The characterization is performed directly on the microsystem, without any post-synthesis processing required. The results show an effect of temperature on the structure of CNTs: high temperature favors thin and regular structures, whereas low temperature favors "bamboo-like" structures.

Compatible immuno-NASBA LOC device for quantitative detection of waterborne pathogens: design and validation.

Waterborne pathogens usually pose a global threat to animals and human beings. There has been a growing demand for convenient and sensitive tools to detect the potential emerging pathogens in water. In this study, a lab-on-a-chip (LOC) device based on the real-time immuno-NASBA (immuno-nucleic acid sequence-based amplification) assay was designed, fabricated and verified. The disposable immuno-NASBA chip is modelled on a 96-well ELISA microplate, which contains 43 reaction chambers inside the bionic channel networks. All valves are designed outside the chip and are reusable. The sample and reagent solutions were pushed into each chamber in turn, which was controlled by the valve system. Notably, the immuno-NASBA chip is completely compatible with common microplate readers in a biological laboratory, and can distinguish multiple waterborne pathogens in water samples quantitatively and simultaneously. The performance of the LOC device was demonstrated by detecting the presence of a synthetic peptide, ACTH (adrenocorticotropic hormone) and two common waterborne pathogens, Escherichia coli (E. coli) and rotavirus, in artificial samples. The results indicated that the LOC device has the potential to quantify traces of waterborne pathogens at femtomolar levels with high specificity, although the detection process was still subject to some factors, such as ribonuclease (RNase) contamination and non-specific adsorption. As an ultra-sensitive tool to quantify waterborne pathogens, the LOC device can be used to monitor water quality in the drinking water system. Furthermore, a series of compatible high-throughput LOC devices for monitoring waterborne pathogens could be derived from this prototype with the same design idea, which may render the complicated immuno-NASBA assays convenient to common users without special training.