Electrical characterization of textile transmission lines

In this paper, electrical characterization and modeling of conductive textiles are presented. A dedicated measurement setup has been developed to allow reliable connection of the textile samples with the equipment cables. Geometrical fabric structures and fabrication tolerances as well as high frequency properties up to 6 GHz for four types of textiles have been determined. Transmission lines with controlled characteristic impedance have been realized enabling the characterization of typical line attenuation factors. This work shows that textile transmission lines can be used for frequencies up to 1.2 GHz and 120 MHz with the maximal lengths of 10 and 100 cm, respectively.     

Exploration of nanostructured channel systems with single-molecule probes

Molecular movement in confined spaces is of broad scientific and technological importance in areas ranging from molecular sieving and membrane separation to active transport through ion channels. Whereas measurements of ensemble diffusion provide information about the overall behaviour of the guest in a porous host, tracking individual molecules provides insight into both the heterogeneity and the mechanistic details of molecular diffusion as well as into the structure of the host. Here, we show how single dye molecules can be used as nanoscale probes to map out the structure of mesoporous silica channel systems prepared as thin films via cooperative self-assembly of surfactant molecules with polymerizable silicate species. The dye molecules act as beacons while they diffuse through the different structural phases of the host: the structure of the trajectories, the diffusivities and the orientation of single molecules are distinctive for molecules travelling in the lamellar and the hexagonal mesophases. These experiments reveal unprecedented details of the host structure, its domains and the accessibility as well as the connectivity of the channel system.     

Liquid-phase chemical and biochemical detection using fully integrated magnetically actuated complementary metal oxide semiconductor resonant cantilever sensor systems

A novel resonant cantilever sensor system for liquid-phase applications is presented. The monolithic system consists of an array of four electromagnetically actuated cantilevers with transistor-based readout, an analog feedback circuit, and a digital interface. The biochemical sensor chip with a size of 3 mm x 4.5 mm is fabricated in an industrial complementary metal oxide semiconductor (CMOS) process with subsequent CMOS-compatible micromachining. A package, which protects the electrical components and the associated circuitry against liquid exposure, allows for a stable operation of the resonant cantilevers in liquid environments. The device is operated at the fundamental cantilever resonance frequency of approximately 200 kHz in water with a frequency stability better than 3 Hz. The use of the integrated CMOS resonant cantilever system as a chemical sensor for the detection of volatile organic compounds in liquid environments is demonstrated. Low concentrations of toluene, xylenes, and ethylbenzene in deionized water have been detected by coating the cantilevers with chemically sensitive polymers. The liquid-phase detection of analyte concentrations in the single-ppm range has been achieved. Furthermore, the application of this sensor system to the label-free detection of biomarkers, such as tumor markers, is shown. By functionalizing the cantilevers with anti-prostate-specific antigen antibody (anti-PSA), the corresponding antigen (PSA) has been detected at concentration levels as low as 10 ng/mL in a sample fluid.     

A Digital CMOS Architecture for a Micro-Hotplate Array

A monolithic gas sensor array fabricated in industrial CMOS technology combined with post-CMOS micromachining is presented. The device comprises an array of three metal-oxide-coated micro-hotplates with integrated MOS transistor heaters and the needed driving and signal-conditioning circuitry. Three digital PID controllers enable individual temperature regulation for each hotplate. The operating temperature of the SnO₂ metal-oxide sensors may amount up to 350degC. A serial interface and the temperature control units have been implemented digitally. Emphasis was put on designing a modular system with the required analog circuitry reduced to a minimum. With its small overall size of 5.5times4.5 mm2, its digital interface and its good hotplate thermal efficiency of 6degC/mW, the system represents a significant development on the way to low-cost mobile gas sensor systems. The limit of detection at constant temperatures has been assessed to be below 1 ppm for CO and approximately 100 ppm for CH₄. The mainly digital implementation with a maximum sampling rate of 9.3 kHz for all three sensors offers the advantage to apply a power-saving mode and temperature modulation techniques to enhance the analyte discrimination capability     

Monomer Recycling and Repolymerization of Post-Consumer Polyester Textiles

Due to the presence of dyes and additives, textile recycling is challenging, therefore the majority of textile waste is downcycled to low-value products, incinerated or landfilled. In this study, a continuous depolymerization of post-consumer polyester textiles was conducted by alkaline hydrolysis. The degree of depolymerization was assessed and found to be 94 %. After recovering and analyzing the terephthalic acid and ethylene glycol the monomers were successfully polymerized to regain a food grade quality recycled polyethylene terephthalate. The presented recycling approach allows a closed-loop recycling of textiles.     

The corrosion of some zirconium alloys under radiation in moist carbon dioxide-air mixtures

In-reactor experiments are reported in which Zircaloy-2 and $\text{Zr-2}\text{1}\text{2}$ wt % Nb alloys were exposed to moist carbon dioxide-air mixtures at 300°C for periods up to ≈ 800 days. For Zircaloy-2 the corrosion was significantly enhanced by the reactor radiation but the percentage hydrogen pick-up was reduced. For $\text{Zr-2}\text{1}\text{2}$ wt % Nb alloy the effect of radiation on the corrosion rate ranged from a slight suppression to a significant enhancement, depending on the metallurgical condition of the alloy, but there appeared to be no effect on the percentage hydrogen pick-up. The effect of improving the purity of the corrodent was also studied in the absence of radiation. The results are used to predict that the corrosion and hydrogen pick-up of typical reactor pressure tubes exposed to moist carbon dioxide-air mixtures are unlikely to cause a significant deterioration of their mechanical properties.     

Three-dimensional numerical modeling of an induction heated injection molding tool with flow visualization

Using elevated mold temperature is known to have a positive influence of final injection molded parts. Induction heating is a method that allow obtaining a rapid thermal cycle, so the overall molding cycle time is not increased. In the present research work, an integrated multi-turn induction heating coil has been developed and assembled into an injection molding tool provided with a glass window, so the effect of induction heating can directly be captured by a high speed camera. In addition, thermocouples and pressure sensors are also installed, and together with the high speed videos, comparison of the induction heating and filling of the cavity is compared and validated with simulations. Two polymer materials ABS and HVPC were utilized during the injection molding experiments carried out in this work. A nonlinear electromagnetic model was employed to establish an effective linear magnetic permeability. The three-dimensional transient thermal field of the mold cavity was then calculated and compared with the experiments. This thermal field was transferred to an injection molding flow solver to compare simulations and experimental results from the high speed video, both with and without the effect of induction heating. A rapid thermal cycle was proved to be feasible in a mold with an integrated induction coil. Furthermore, it was shown that the process can be modeled with good accuracy, both in terms of the thermal field and of the flow pattern.     

Layer-by-layer deposition of J-aggregates and polyelectrolytes for electroluminescence applications: A spectroscopic study

The self-assembly method of layer-by-layer deposition of oppositely charged polyelectrolytes is used to insert J-aggregates of the dye tetrachloro-diethyl-disulfobutyl-benzimido-carbocyanine (TDBC) into thin polymeric films. The J-aggregates are characterized by a narrow absorption- and fluorescence band with its maximum at 590 nm, which is red-shifted with respect to the monomeric transition at 515 nm. The dyes are either coadsorbed with the polyelectrolytes poly(allylamine hydrochloride (PAH) and poly(styrene sulfonate) (PSS), or alternately deposited with the precursor of poly(phenylene vinylene) (pre-PPV). The optical properties of the aggregates are not changed significantly by the deposition process. The pre-PPV/TDBC films are heated under vacuum to convert the PPV to its conjugated form. The resulting films can be used for the fabrication of light-emitting devices. The optical properties such as fluorescence and electroluminescence are dominated by the J-aggregates. The excitation energy of PPV is transferred to the dye aggregates with an efficiency of 100%. The electroluminescence is not very stable and shows a very slow turn-on time. However, the combination of self-assembled PPV/TDBC layers with a spin-coated film of PPV results in stable electroluminescence emission under ambient conditions. In this case, light is emitted from both species, the PPV and the J-aggregates, whereas the ratio of the two intensities strongly depends on temperature.     

Organic field effect transistors for textile applications.

In this paper, several issues concerning the development of textiles endowed with electronic functions will be discussed. In particular, issues concerning materials, structures, electronic models, and the mechanical constraints due to textile technologies will be detailed. The idea starts from an already developed organic field-effect transistor that is realized on a flexible film that can be applied, after the assembly, on whatever kind of substrate, in particular, on textiles. This could pave the way to a variety of applications aimed to conjugate the favorable mechanical properties of textiles with the electronic functions of transistors. Furthermore, a possible perspective for the developments of organic sensors based on this structure are described.