Multichannel microchip electrophoresis device fabricated in polycarbonate with an integrated contact conductivity sensor array

A 16-channel microfluidic chip with an integrated contact conductivity sensor array is presented. The microfluidic network consisted of 16 separation channels that were hot-embossed into polycarbonate (PC) using a high-precision micromilled metal master. All channels were 40 microm deep and 60 microm wide with an effective separation length of 40 mm. A gold (Au) sensor array was lithographically patterned onto a PC cover plate and assembled to the fluidic chip via thermal bonding in such a way that a pair of Au microelectrodes (60 microm wide with a 5 microm spacing) was incorporated into each of the 16 channels and served as independent contact conductivity detectors. The spacing between the corresponding fluidic reservoirs for each separation channel was set to 9 mm, which allowed for loading samples and buffers to all 40 reservoirs situated on the microchip in only five pipetting steps using an 8-channel pipettor. A printed circuit board (PCB) with platinum (Pt) wires was used to distribute the electrophoresis high-voltage to all reservoirs situated on the fluidic chip. Another PCB was used for collecting the conductivity signals from the patterned Au microelectrodes. The device performance was evaluated using microchip capillary zone electrophoresis (mu-CZE) of amino acid, peptide, and protein mixtures as well as oligonucleotides that were separated via microchip capillary electrochromatography (mu-CEC). The separations were performed with an electric field (E) of 90 V/cm and were completed in less than 4 min in all cases. The conductivity detection was carried out using a bipolar pulse voltage waveform with a pulse amplitude of +/-0.6 V and a frequency of 6.0 kHz. The conductivity sensor array concentration limit of detection (SNR = 3) was determined to be 7.1 microM for alanine. The separation efficiency was found to be 6.4 x 10(4), 2.0 x 10(3), 4.8 x 10(3), and 3.4 x 10(2) plates for the mu-CEC of the oligonucleotides and mu-CZE of the amino acids, peptides, and proteins, respectively, with an average channel-to-channel migration time reproducibility of 2.8%. The average resolution obtained for mu-CEC of the oligonucleotides and mu-CZE of the amino acids, peptides, and proteins was 4.6, 1.0, 0.9, and 1.0, respectively. To the best of our knowledge, this report is the first to describe a multichannel microchip electrophoresis device with integrated contact conductivity sensor array.     

Highly Occupied Surface States at Deuterium-Grown Boron-Doped Diamond Interfaces for Efficient Photoelectrochemistry

Polycrystalline boron-doped diamond is a promising material for high-power aqueous electrochemical applications in bioanalytics, catalysis, and energy storage. The chemical vapor deposition (CVD) process of diamond formation and doping is totally diversified by using high kinetic energies of deuterium substituting habitually applied hydrogen. The high concentration of deuterium in plasma induces atomic arrangements and steric hindrance during synthesis reactions, which in consequence leads to a preferential (111) texture and more effective boron incorporation into the lattice, reaching a one order of magnitude higher density of charge carriers. This provides the surface reconstruction impacting surficial populations of C C dimers, C H, CO groups, and  COOH termination along with enhanced kinetics of their abstraction, as revealed by high-resolution core-level spectroscopies. A series of local densities of states were computed, showing a rich set of highly occupied and localized surface states for samples deposited in deuterium, negating the connotations of band bending. The introduction of enhanced incorporation of boron into (111) facet of diamond leads to the manifestation of surface electronic states below the Fermi level and above the bulk valence band edge. This unique electronic band structure affects the charge transfer kinetics, electron affinity, and diffusion field geometry critical for efficient electrolysis, electrocatalysis, and photoelectrochemistry.     

Fluctuation-enhanced scent sensing using a single gas sensor

Scent or aroma sensing during aromatherapy can be carried out by applying only a single resistance gas sensor (TGS - Taguchi Gas Sensors). This paper considers the efficiency of detection of essential oils by DC resistance and its fluctuations observed in TGS sensors. A detailed study has been conducted for scents emitted by five popular essential oils using three sensor types (TGS 2600, TGS 2602, TGS 823). The research was focused on the practical use in aromatherapy to assure the same intensity of scents which are sprayed by a glass nebulizer. The prepared system for scent emission and control of its intensity was presented as well.     

A Coupled Thermal/Material Flow Model of Friction Stir Welding Applied to Sc-Modified Aluminum Alloys

A coupled thermal/material flow model of friction stir welding was developed and applied to the joining of Sc-modified aluminum alloy (7042-T6) extrusions. The model reveals that surface material is pulled from the retreating side into the weld zone where it is interleaved with in situ material. Due to frictional contact with the shoulder, the surface material is hotter than the in situ material, so that the final weld microstructure is composed of bands of material with different temperature histories. For this alloy and the associated FSW heating rates, secondary phase dissolution/precipitation temperatures are in proximity to the welding temperatures. Therefore, depending on the surface and in situ material temperatures in relation to these transformation temperatures, disparate precipitate distributions can develop in the bands of material comprising the weld nugget. Based on the numerical simulation and on thermal analysis data from differential scanning calorimetry, a mechanism for the formation of onion rings within the weld zone is presented.     

An integrated model for the transshipment yard scheduling problem

A hub-and-spoke railway system is an efficient way of handling freight transport by land. A modern rail–rail train yard consists of huge gantry cranes that move the containers between the trains. In this context, we consider a rail–rail transshipment yard scheduling problem (TYSP) where the containers arrive to the hub and need to be placed on a train that will deliver them to their destination. In the literature, the problem is decomposed hierarchically into five subproblems, which are solved separately. First, the trains have to be grouped into bundles in which they visit the yard. Next, the trains have to be assigned to tracks within these bundles, namely parking positions. Then the final positions for the containers on trains have to be determined. Next, the container moves that need to be performed are assigned to the cranes. Finally, these moves have to be sequenced for each crane for processing. In this paper, an integrated MILP model is proposed, which aims to solve the TYSP as a single optimization problem. The proposed formulation also enables us to define more robust and complex objective functions that include key characteristics from each of the above-mentioned subproblems. The strength of our proposed formulation is demonstrated via computational experiments using the data from the literature. Indeed, the results show that the TYSP can be solved without the use of decomposition techniques and more insight can be obtained from the same input data used to solve particular single decomposed subproblems.     

Evaluation of micromilled metal mold masters for the replication of microchip electrophoresis devices

High-precision micromilling was assessed as a tool for the rapid fabrication of mold masters for replicating microchip devices in thermoplastics. As an example, microchip electrophoresis devices were hot embossed in poly(methylmethacrylate) (PMMA) from brass masters fabricated via micromilling. Specifically, sidewall roughness and milling topology limitations were investigated. Numerical simulations were performed to determine the effects of additional volumes present on injection plugs (i.e., shape, size, concentration profiles) due to curvature of the corners produced by micromilling. Elongation of the plug was not dramatic (< 20%) for injection crosses with radii of curvatures to channel width ratios less than 0.5. Use of stronger pinching potentials, as compared to sharp-corner injectors, were necessary in order to obtain short sample plugs. The sidewalls of the polymer microstructures were characterized by a maximum average roughness of 115 nm and mean peak height of 290 nm. Sidewall roughness had insignificant effects on the bulk EOF as it was statistically the same for PMMA microchannels with different aspect ratios compared to LiGA-prepared devices with a value of ca. 3.7 × 10⁻⁴ cm²/(V s). PMMA microchip electrophoresis devices were used for the separation of pUC19 Sau3AI double-stranded DNA. The plate numbers achieved in the micromilled-based chips exceeded 1 million/m and were comparable to the plate numbers obtained for the LiGA-prepared devices of similar geometry.     

Sentiment Analysis as a Source of Gaining Competitive Advantage on the Electricity Markets

The electricity retail markets are evolving toward more competitive and customer-oriented. The deployment of smart meters and a wealth of new technologies create customers' eagerness for taking control of their electricity consumption. By being better-informed about the energy usage, people are encouraged to switch deals among existing suppliers or move to a new energy provider. Moreover, as customers are more socially interconnected, the Internet portals and social media become a place for discussion, comparison, and evaluation of the available offers. Unfortunately, in case of the energy sector there is a lack of understanding that such information, when taken into account and properly analyzed, can be a completely new and a powerful source of competitive advantage.In the paper, we introduce a solution that the use of quasi real-time automated sentiment analysis on the energy suppliers and the relevant aspects of their offers may enable energy companies to adapt quickly to changing circumstances, prevent potential customer churn, and harness new business opportunities.     

Electromagnetic Pump Made in a Hybrid Polymer-Ceramic Technology--Preliminary Results

This paper describes technology of the electromagnetic pump made in a hybrid polymer-ceramic technology. The pumping mechanism is realized with a mutual excitation between an electromagnetic coil and a neodymium magnet bonded to a flexible membrane. A PDMS （poly（dimethylsiloxane）） material was used to manufacture a membrane sufficient for the presented micropump. A fish trap construction is adapted to the ceramic technology. The bonding process of ceramics and polymer, using plasma oxidation method, is described as well. Moreover, a membrane deflection depending on magnet dimensions and applied voltage was measured.     

Micro Ceramic Cell Analyzer (MCCA) - Preliminary results

This paper describes the preliminary results of a detection module for a Micro Ceramic Cell Analyzer (MCCA) development and fabrication process. The detector with integrated light source (electroluminescence diode) and photodetector (light-to-voltage converter) is made using Low Temperature Co-fired Ceramics (LTCC) technology. The presented device is assigned for use in fluorescence activated cell detection. Its performance is examined experimentally for two test solutions, which consist of Escherichia coli and Saccharomyces cervisiae cells. Investigated biological material is marked using the DAPI (4′, 6-diamidino-2′-phenylindole, dihydrochloride) fluorescent stain. After exposure to a 370 nm excitation light, the cells bonded with DAPI fluorescent blue (460 nm). Using the photodetector, fluorescence intensity was found to be proportional to the number of the cells in the test solutions.     

High Frequency Solution-Processed Organic Field-Effect Transistors with High-Resolution Printed Short Channels

Organic electronics is an emerging technology that enables the fabrication of devices with low-cost and simple solution-based processes at room temperature. In particular, it is an ideal candidate for the Internet of Things since devices can be easily integrated in everyday objects, potentially creating a distributed network of wireless communicating electronics. Recent efforts allowed to boost operational frequency of organic field-effect transistors (OFETs), required to achieve efficient wireless communication. However, in the majority of cases, in order to increase the dynamic performances of OFETs, masks based lithographic techniques are used to reduce device critical dimensions, such as channel and overlap lengths. This study reports the successful integration of direct written metal contacts defining a 1.4 µm short channel, printed with ultra-precise deposition technique (UPD), in fully solution fabricated n-type OFETs. An average transition frequency as high as 25.5 MHz is achieved at 25 V. This result demonstrates the potential of additive, high-resolution direct-writing techniques for the fabrication of organic electronics operating in the high-frequency regime.