Lab-on-a-disc for fully integrated multiplex immunoassays

This paper presents a cost-effective, rapid, and fully automated lab-on-a-disc for simultaneous detection of multiple protein biomarkers in raw samples such as whole blood or whole saliva. For the diagnosis of cardiovascular disease, here, a novel centrifugal microfluidic layout was designed to conduct the simultaneous detection of high sensitivity C-reactive protein, cardiac troponin I, and N-terminal pro-B type natriuretic peptide based on a bead-based sandwich type enzyme-linked immunosorbent assay (ELISA). Three reaction chambers are initially interconnected for the common processes such as sample injection, incubation, and washing and then isolated on-demand for the independent processes such as substrate incubation and final detection. The assay performances such as the limit of detection and the dynamic range were comparable with those of the conventional ELISA despite the significant reduction of the minimum sample volume (200 μL), the amount of washing buffer (700 μL), and the total process time (20 min).     

Low-power 2-D fully integrated CMOS fluxgate magnetometer

In this paper, we present a low-power, two-axis fluxgate magnetometer. The planar sensor is integrated in a standard CMOS process, which provides metal layers for the coils and electronics for the signal extraction and processing. The ferromagnetic core is placed diagonally above the four excitation coils by a compatible photolithographic post process, performed on a whole wafer. The sensor works using the single-core principle, with a modulation technique to lower the noise and the offset at the output. In contrast to traditional fluxgate approaches, the sensor features a high degree of integration and minimal power consumption at 2.5 V of supply voltage that makes it suitable for portable applications. A novel digital feedback principle is integrated to linearize the sensor characteristics and to extend the linear working range.     

Aluminum alloying in silicon integrated circuits

The metallization step in the fabrication of silicons devices and integrated circuits requires the alloying of silicon to aluminium to create ohmic contacts in the window regions. This heat treatment often results “spearing” which, especially in integrated circuits, represents a significant failure mode. The topology and kinetics of the spearing process are discussed and evidence is presented which tendsto suggest a liquid phase reaction between silicon and aluminium. A variety of metallization techniques, involving aluminium, by which it is believed spearing can be prevented are also discussed.     

A fully integrated temperature compensation technique forpiezoresistive pressure sensors

A fully integrated temperature compensation technique for piezoresistive pressure sensors is presented. The technique is suitable for batch fabricated sensors operable over a temperature range of -40°C-130°C and a pressure range of 0-310 kPa. The implementing hardware for the technique is developed and verified through PSpice and VHDL simulations. The technique is very effective for pressure values below 240 kPa and provides reasonable results for higher pressures. The technique is structurally simple and uses standard IC fabrication technologies     

Toward a fully integrated positive-pressure driven microfabricated liquid analyzer.

A versatile integrated analyzer with a flow-programmed injection strategy and multiwavelength detection is described with applications toward sampling, flow injection analysis, and capillary separations. Continuous near-real-time sampling is a major benefit of the flow-programmed injection technique. Injection volumes ranging from 250 pL to several microliters were made without electrophoretic flow. Multiwavelength grating light reflection spectroscopy (GLRS) and transmission absorbance spectroscopy were performed simultaneously in a detection volume of 150 pL. The utility of these detection methods for refractive index (RI) and absorbance detection in capillary channels is demonstrated through analysis of salt, indicator, and dyes. GLRS is a unique, selective, and path-length-independent technique for probing RI, absorbance, and other optical properties. A limit of detection (LOD) of 170 microM was achieved for GLRS interferometric detection of FD&C Red #3, which corresponded to 2.6 fmol of analyte in the 150-pL detection volume. A LOD of 2 mM for phosphate buffer, or 3 fmol in the 150-pL detection volume will also be demonstrated. A siloxane coating on the GLRS grating was employed as a sensing layer to probe interactions between the sample and stationary phase. The combined GLRS interferometric response provided insight into both optical and chromatographic properties of samples. Open tubular capillary liquid chromatography with multidimensional multiwavelength detection is demonstrated for the analysis of three food dyes. Separation efficiency, N, of 16,000 was achieved for an unretained dye peak eluting at 12 min. Integration of novel sampling and detection schemes makes this a broadly applicable liquid analyzer.     

A fully integrated monolithic microchip electrospray device for mass spectrometry

A novel microfabricated nozzle has been developed for the electrospray of liquids from microfluidic devices for analysis by mass spectrometry. The electrospray device was fabricated from a monolithic silicon substrate using deep reactive ion etching and other standard semiconductor techniques to etch nozzles from the planar surface of a silicon wafer. A channel extends through the wafer from the tip of the nozzle to a reservoir etched into the opposite planar surface of the wafer. Nozzle diameters as small as 15 microm have been fabricated using this method. The microfabricated electrospray device provides a reproducible, controllable, and robust means of producing nano-electrospray of a liquid sample. The electrospray device was interfaced to an atmospheric pressure ionization time-of-flight mass spectrometer using continuous infusion of test compounds at low nanoliter-per-minute flow rates. Nozzle-to-nozzle signal intensity reproducibility using 10 nozzles was demonstrated to be 12% with single-nozzle signal stability routinely less than 4% relative standard deviation (RSD). Solvent compositions have been electrosprayed ranging from 100% organic to 100% aqueous. The signal-to-noise ratio from the infusion of a 10 nM cytochrome c solution in 100% water at 100 nL/min was 450:1. Microchip electrospray nozzles were compared with pulled capillaries for overall sensitivity and signal stability for small and large molecules. The microchip electrospray nozzles showed a 1.5-3-times increase in sensitivity compared with that from a pulled capillary, and signal stability with the microchip was 2-4% RSD compared with 4-10% with a pulled capillary. Electrospray device lifetimes achieved thus far have exceeded 8 h of continuous operation and should be sufficient for typical microfluidic applications. The total volume of the electrospray device is less than 25 pL, making it suitable for combination with microfluidic separation devices.     

Cooled photodiodes based on a type-II single p-InAsSbP/n-InAs heterostructure

Analysis of current-voltage and spectral characteristics of photodiodes based on a single p-InAsSbP/n-InAs heterostructure formed on a heavily doped n ⁺-InAs substrate (n ⁺ ～ 10¹⁸ cm^?3) is presented. It is shown that, at low temperatures (77 < T < 190 K), the generation-recombination current flow mechanism typical of p-i-n diodes dominates. Expected parameters of the photodiode that can be obtained using these heterostructures are presented.     

Erbium-doped oxidized porous silicon for integrated optical waveguides

It is shown for the first time that introducing erbium lectrochemically into waveguide structures based on oxidized porous silicon not only preserves their waveguide properties but it also opens up prospects for producing active waveguide devices based on them. It is established that erbium in a waveguide is in an optically active state and light with wavelengths 381 and 523 nm excites the erbium ions most efficiently. Pis’ma Zh. Tekh. Fiz. 25, 69–73 (September 12, 1999)     

Megavolt arsenic implantation into silicon

Implantations of arsenic at 11 MeV have been performed into Si(100) substrates at room and liquid nitrogen temperatures. The residual damage after annealing has been observed using Rutherford backscattering and cross-sectional transmission electron microscopy. In situ annealing is shown to be more important for room temperature implantation compared with liquid nitrogen temperature implantation. Spreading resistance has been used to determine active carrier concentrations, and the measured range of 4.4 μm agrees with Linhard-Scharff-Schi?tt calculations. Buried interconnects with a sheet resistance of 50 Ω/? have been fabricated and tested.     

Micromachined silicon electrolytic conductivity probes with integrated temperature sensor

Electrolytic conductivity measurements of fluids currently require sample volumes greater than a milliliter. Many applications would benefit from accurate measurements of nano- to microliter sample volumes. However, polarization and nonlinear electrode impedance effects, along with stray impedance and temperature effects, strongly affect measurements of the solution conductance for microliter and smaller sample volumes. MEMS-based silicon electrolytic conductivity probes, down to 100-/spl mu/m wide, with integrated temperature sensors, have been designed and fabricated to overcome these effects. Several electrode configurations were tested: plain electrode pairs, electrode pairs plated with platinum black, plain four electrode sets, and four electrode sets plated with platinum black were investigated. The same accuracy as normal scale probes has been achieved with these sensors over almost three orders of magnitude in solution concentration and electrolytic conductivity ranges.     

Comparative study of terahertz radiation from n-InAs and n-GaAs

We have studied terahertz (THz) emissions from n-InAs and n-GaAs using an ensemble Monte Carlo method. Our simulations indicate that higher amplitude THz waves from n-InAs, compared with those from n-GaAs, result from the difference in the radiation mechanisms between these two samples and are not completely dependent on the most commonly recognized fact: lighter electron effective mass in n-InAs. The excitation-wavelength-dependent and doping-level-dependent THz emissions from n-InAs are found to be quite different from those from n-GaAs. The corresponding mechanisms are analyzed by the introduction of a weighted electric field, which is weighted by the photogenerated carrier density in a semiconductor. The simulated results are in good qualitative agreement with experimental observations from other authors.     

Diffusion of aluminum into silicon nitride films

Aluminum diffusion into silicon nitride films at temperatures in the range 450–530°C was studied by Auger electron spectroscopy in conjunction with depth profiling. The activation energy for the diffusion of aluminum and the diffusion coefficient were found to be 2.0±0.3 eV and (7.3±3.5) x 10^-3 cm² s^-1, respectively. The chemical effects in the KLL aluminum Auger spectra together with the compositional depth profiles suggest that the migration of aluminum is dominated by volume diffusion which involves the reaction of aluminum with oxygen.     

Time-resolved penetration into pre-damaged hot-pressed silicon carbide

We have conducted a series of experiments to examine projectile penetration of cylindrical hot-pressed silicon carbide (SiC) ceramic targets that are pre-damaged to varying degrees under controlled laboratory conditions prior to ballistic testing. SiC was thermally shocked to introduce non-contiguous cracks. Another set of targets was thermally shocked and then additional damage was induced by load–unload cycling in an MTS machine while the ceramic specimen was confined in a 7075-T6 aluminum sleeve. Finally, targets were made by compacting SiC powder into a 7075-T6 aluminum sleeve. For each of these target types, long gold rod penetration was measured as a function of impact velocity v_p over the approximate range of 1–3 km/s, with most data between 1.5 and 3 km/s. Penetration as a function of time was measured using multiple independently timed flash X-rays. Results are compared with previous results for non-damaged (intact) SiC targets. Key results from these experiments include the following: (1) penetration is nominally steady state for v_p>1.5 km/s; (2) for all target types, the penetration velocity u is a linear function of v_p (except for the lowest impact velocities); and (3) it is found that u_intact<u_pre-damaged<u_{in-situ comminuted}<u_powder<u_hydrodynamic.     

Simulation and performance evaluation of partially and fully integrated sales and operations planning

This article presents rolling horizon simulation models and performance analysis of partially and fully integrated sales and operations planning (S&OP) against traditional decoupled planning in a multi-site make-to-order (MTO) based manufacturing supply chain. Three simulation models are developed illustrating, respectively, the fully integrated S&OP model, which integrates cross-functional planning of sales, production, distribution, and procurement centrally; the partially integrated S&OP model, in which the joint sales and production planning is performed centrally while distribution and procurement are planned separately at each site; and the decoupled planning model, in which sales planning is carried out centrally while production, distribution, and procurement are planned separately and locally. A solution procedure is provided for each model so that a more realistic planning process can be simulated. Performances of rolling horizon simulation models are evaluated against those of the fixed horizon deterministic models. The results demonstrate that while deterministic models are important for theoretical studies, they are insufficient for decision support and performance evaluations in a real business environment. A rolling horizon simulation model is required to provide more realistic solutions. The effects of demand uncertainties and forecast inaccuracies are incorporated in the evaluation. The study is carried out based on a real industrial case of a Canadian-based oriented strand board (OSB) manufacturing company.     

Large arrays of spatial light modulators hybridized to silicon integrated circuits

Large, high-frame-rate spatial light modulators are key components required for the realization of real-time optical processors. We report a 128 × 128 array of GaAs-based optical modulators that we hybridized to a Si integrated circuit by using In bump bonds to form a spatial light modulator. These optical modulators are composed of a series of quantum wells within an asymmetric Fabry-Perot cavity to control the optical properties. The resulting 128 × 128 element array operates in an intensity-only reflection mode at greater than 100,000 frames per second. This array interfaces to a 486-based personal computer through a standard industry standard architecture bus.