Decomposition without aggregation for performance approximation in queueing network models of semiconductor manufacturing

Accurate and speedy forecasts of production cycle time are key components that support the operation of modern semiconductor wafer fabricators. Estimates of cycle time can be obtained via simulation, but such an approach, though common, requires significant computational investment and model maintenance. Queueing network models and approximations for their performance can provide a viable alternative. As modern semiconductor manufacturing systems exhibit largely reentrant product routing, but contain essential probabilistic routes (for metrology and rework), prior mean cycle time approximation methods are not well suited to the system structure. In this paper, we extend the decomposition without aggregation (DWOA) approach – which is tailored to systems with deterministic routing – to allow for the existence of probabilistic paths. Numerical and simulation studies are conducted with numerous practically inspired datasets to assess the quality of the resulting mean cycle time approximations. The results reveal that our approach outperforms the existing mean cycle time approximations on datasets inspired by the semiconductor industry MIMAC benchmark datasets. For example, in MIMAC dataset 1, our mean cycle time approximations exhibit an average of 10.33% error compared to 18.82% error for existing approaches.     

Photonic crystal fiber sensors for minimally invasive surgical devices

The measurement of interaction forces in minimally invasive surgical devices, sensorized with photonic crystal fiber (PCF) sensors, is presented in this paper. Two types of PCF sensors are used: a tapered PCF interferometer and a microhole-collapsed PCF interferometer for the detection of interaction forces generated in surgical devices without the influence of ambient temperature variation. The demonstration devices used for force characterization are a laparoscopic scissor and a standard surgical scissor blade. The force sensitivity of each sensorized blade is examined and compared with fiber Bragg grating (FBG)-sensorized blades. Results show that the PCF-sensorized surgical blades outperform the blades fitted with the FBG sensors during static load measurement.     

Nonenzymatic ligation of DNA with a reversible step and a final linkage that can be used in PCR

Nonenzymatic DNA ligation chemistries containing a reversible step allow thermodynamic control of product formation, but they are not necessarily compatible with polymerase enzymes. We report a ligation system that uses commercially available reagents, includes a reversible step, and results in a linkage that can function as a template for PCR amplification with accurate sequence transfer.     

Microfluidic flow cytometer for quantifying photobleaching of fluorescent proteins in cells

Traditional flow cytometers are capable of rapid cellular assays on the basis of fluorescence intensity and light scatter. Microfluidic flow cytometers have largely followed the same path of technological development as their traditional counterparts; however, the significantly smaller transport distance and resulting lower cell speeds in microchannels provides for the opportunity to detect novel spectroscopic signatures based on multiple, nontemporally coincident excitation beams. Here, we characterize the design and operation of a cytometer with a three-beam, probe/bleach/probe geometry, employing HeLa suspension cells expressing fluorescent proteins. The data collection rate exceeds 20 cells/s under a range of beam intensities (5 kW to 179 kW/cm(2)). The measured percent photobleaching (ratio of fluorescence intensities excited by the first and third beams: S(beam3)/S(beam1)) partially resolves a mixture of four red fluorescent proteins in mixed samples. Photokinetic simulations are presented and demonstrate that the percent photobleaching reflects a combination of the reversible and irreversible photobleaching kinetics. By introducing a photobleaching optical signature, which complements traditional fluorescence intensity-based detection, this method adds another dimension to multichannel fluorescence cytometry and provides a means for flow-cytometry-based screening of directed libraries of fluorescent protein photobleaching.     

The properties and applications of nanodiamonds

Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. They are also non-toxic, which makes them well suited to biomedical applications. Here we review the synthesis, structure, properties, surface chemistry and phase transformations of individual nanodiamonds and clusters of nanodiamonds. In particular we discuss the rational control of the mechanical, chemical, electronic and optical properties of nanodiamonds through surface doping, interior doping and the introduction of functional groups. These little gems have a wide range of potential applications in tribology, drug delivery, bioimaging and tissue engineering, and also as protein mimics and a filler material for nanocomposites.     

Simulation of Impedance Spectra for a Full Three‐Dimensional Ceramic Microstructure Using a Finite Element Model

A method of characterizing electrically heterogeneous electroceramics for a full three‐dimensional collection of randomly shaped grains is presented. Finite element modeling, solving Maxwell's equations in space and time is used to simulate impedance spectroscopy (IS) data. This technique overcomes several deficiencies associated with previous methods used to simulate IS data and allows comprehensive treatment of a full three‐dimensional granular representation of ceramic microstructure without the requirement for equivalent circuits based on the Brickwork layer model (BLM) or the introduction of constant phase elements to describe any nonideality of the IS response. This is applied to a full three‐dimensional ceramic microstructure with varying grain size and electrical properties to generate IS plots that highlight limitations of the BLM in data analysis.     

Fabrication technology for single-material MEMS using polycrystalline diamond

Diamond, due to its large band gap of 5.5 eV, offers the possibility of making MEMS structures out of a single material by varying the doping level to achieve the semiconducting, metallic and insulating (undoped) properties needed in a typical MEMS structure. Polycrystalline diamond (poly-C) is inexpensive and retains many of the unique properties of single-crystal diamond. However, the development of diamond-based single-material MEMS (SMM) technology faces two major challenges; (a) producing highly-insulating and highly-conducting poly-C films in a multilayer structure and (b) developing dry-etching technology to produce multilayer structures made of poly-C. Furthermore, poly-C can be layered to perform a number of functions, whereas a complex stack of materials would otherwise be required. Consequently, due to poly-C's high selectivity as a masking material, the SMM fabrication process developed in the current work allows the reduction of the number of fabrication masks by a factor of 1.5–2 as compared to that used in a conventional MEMS process. A number of complex poly-C SMM structures were fabricated using SiO₂ as a sacrificial layer to address the SMM related issues in a single paper.     

Top notch design for fiber-loop cavity ring-down spectroscopy

Fiber-loop cavity ring-down spectroscopy (CRDS) is a highly sensitive spectroscopic absorption technique which has shown considerable promise for the analysis of small-volume liquid samples. We have developed a new light coupling method for fiber-loop CRDS, which overcomes two disadvantages of the technique: low efficiency light coupling into the cavity and high loss per pass. The coupler is based on a 45° reflective notch polished between 10 and 30 μm into the core of a large-core-diameter (365 μm) optical fiber, and allows for nearly 100% light coupling into the cavity, with a low loss per pass (<4%). The coupler has the additional advantage that the input and output light is spatially separated on opposite sides of the fiber. The detection sensitivity of a fiber-loop CRD spectrometer employing the new coupling method is established from ring-down measurements on aqueous rhodamine 6G (Rh6G) at 532 nm. The results are compared with data obtained using the same light source and detector, but a conventional bend-coupled small-core-diameter (50 μm) optical fiber loop. With our new coupler, a detection limit of 0.11 cm(-1) is found, which corresponds to detection of 0.93 μM Rh6G in a volume of only 19 nL. This is an improvement of over an order of magnitude on our bend-coupled small-core optical fiber results, in which a detection limit of 5.3 cm(-1) was found, corresponding to a detection of 43 μM Rh6G in a volume of 20 pL.