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- 1.9 Chemische und optische Sensorik (17) (entfernen)
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Additive Manufacturing (AM) becomes widespread in many technological fields including the precise machining of steel. To assure quality of final products, thorough monitoring of online process is required. We test several monitoring techniques during the AM printing to quickly detect and possibly correct flaws while building a workpiece. Here we show how optical emission spectroscopy can be used to recognize defects that are artificially introduced on a steel printing substrate.
Vor dem Hintergrund der einzigartigen Modularität, hohen Empfindlichkeit und Selektivität von Antikörper‐gesteuerten Indikatorfreisetzungssystemen (gAID‐Systemen) wurde hier ein Multiplex‐Assay für drei organische Explosivstoffmoleküle (TATP, TNT, PETN) entwickelt, der es erlaubt, die Analyten gleichzeitig in flüssiger Phase mit einem einzelnen Teststreifen und einem Fluoreszenzlesegerät bzw. Smartphone als Detektor in Konzentrationen bis in den unteren ppb‐Bereich in <5 min nachzuweisen. Alle drei Systeme, darunter die hier neu entwickelten Systeme für TNT und PETN, tolerieren zudem nicht nur gepufferte wässrige Modelllösungen, sondern auch komplexere Matrices. Neben einem konventionellen Teststreifen mit einem Kanal erlaubte uns die Anwendung von Wachsdrucktechnologie das Herstellen von mehrkanaligen Streifen mit vergleichbarer analytischer Leistungsfähigkeit, was das enorme Potenzial der modular aufgebauten, hybriden Biosensormaterialien im Hinblick auf eine für den Endanwender maßgeschneiderte Vor‐Ort‐Analytik unterstreicht.
We run two pilot LIP experiments in reactive gas mixtures. First, LIP is excited in BCl3 or BF3 plus H2 or CH4 to evaluate the efficiency of deposition of solid boron and boron carbide, materials that are largely used for refractory coatings. Second, we investigate a possibility of synthesis of fluorochlorosilanes SiFxCl4-x (x = 1, 2, 3) by LIP induced in SiF4+SiCl4 gas mixtures. Using fluorochlorosilanes with different combinations of F and Cl in the SiFxCly molecule may add flexibility in processes of silicon deposition and etching. The gases used and solid deposits are analyzed by optical emission spectroscopy (OES) and IR and mass spectrometry (MS). We also model the laser induced plasma by performing static equilibrium chemistry calculations to see whether desired reaction products are thermodynamically favorable and dynamic calculations of the expanding plasma plume to see how and where the products form.
The globe's seas were used as dumping ground after the world wars and those millions of ammunition, most of all containing 2,4,6-trinitrotoluene (TNT), represent a pressing danger for fishermen, dredging operations, submarine cable installations and tourism. We developed an extremely selective indication method for TNT based on a specific reaction that produces a highly fluorescent compound. The indication system was integrated into a microfluidic PDMS chip for the solid-liquid extraction of TNT from water samples, offering environmental monitoring possibilities. Combining the advantages of a light-up indicator, microfluidics and a smartphone as detector, the embedded sensor allows for the remote and rapid detection of TNT down to ng in surface and sea waters.
Die räumlich aufgelöste Heterodyn-Spektroskopie (SHS) kombiniert dispersive und interferometrische Techniken zur Gewinnung spektroskopischer Informationen und kann in einem anpassbaren Instrument realisiert werden. SHS wird für die chemische Analyse von verschiedenen Materialien mit Hilfe der Laser-induzierten Plasmaspektroskopie (LIBS) und der Raman-Spektroskopie eingesetzt.
Sensors are the scientific and technological extension of human senses and enormously expand human capabilities. Despite the fact that scientific and technological advances are usually seen in a positive light, the name of this conference, Sensors for Good, put me in a bit of a trouble, because in general science does not operate in ethical categories, but instead it just tells how far from the truth one is. In this respect, sensors help us in recognizing states and events beyond our immediate reach. Fortunately, sensors are used for many applications, such as environmental monitoring, food control, and alike, which unequivocally benefit society.
I will focus on a particular type of sensors, those that rely on microfluidics for operation and which are typically realized in lab-on-a-chip (LOC) devices. In this domain, where at least one of the dimensions through which a fluid flows is submillimetric, our natural senses fail, because the phenomena are too small to be detected either by eye, smell, touch, and even the common sense explanation that we learn for many years in school is not applicable, because the phenomena are dominated by different parameters. To give one simple example, in general the direction of flow in microfluidic channels does not depend on the up-down direction of the channel, because gravitational force or the weight of the fluid is negligible compared to the viscous forces present on the chip.
This presentation consists of three parts: initially, two sensors produced in our lab are presented, followed by a simulation oriented discussion on microfluidics and biosensors, and finally a project in progress that we are involved in is presented, concluding with a list of open issues raised during the presentation.
Methods for the rapid and sensitive detection of target analytes are gaining importance in medical diagnostics and environmental monitoring, in the security, occupational health and safety as well as food sectors. Among all the methods employed for rapid tests, lateral flow assays (LFAs) are the most commonly used. However, some drawbacks are that most of these tests either indicate the analyte only indirectly, and in other cases the sensitivity is not high enough.
Keeping in mind these limitations, the use of stimuli-responsive materials for small-molecule sensing relying on chemical signal amplification and utilizing specific interactions between biomolecules such as antibodies and the corresponding analytes are particularly attractive. Such materials can also be incorporated on paper strips for lateral-flow assays in a straightforward manner. These sensing materials comprise mesoporous silica nanoparticles loaded with indicator molecules and containing certain hapten derivative molecules covalently grafted at the surface, which bind to the respective antibody and inhibit the release of a dye as reporter (Scheme 1). In presence of the designated analyte, a displacement of the antibody from the material is observed, allowing the release of dye. Because a large number of indicator molecules can be released when a single analyte molecule binds to an antibody cap, a strong signal amplification is observed.
Considering the modularity, high sensitivity and selectivity of these antibody-gated indicator delivery systems, the presentation discusses general aspects of system design as well as analytical performance and highlights the integration into a lateral-flow assay, showing as an example the determination of the explosives TATP, TNT and PETN with a fluorescence readout, in single-substance and multiplexing modes.
A possibility of deposition from laser-induced plasma (LIP) is investigated in search for an economic and simple method to obtain isotopic compounds from enriched gaseous precursors. A breakdown in mixtures of BCl3 and BCl3 with hydrogen, argon, and methane are studied both theoretically and experimentally. Calculations of expanding plasma of different composition are performed with the use of the fluid dynamic code coupled to the equilibrium chemistry solver. Condensed phases of boron, boron carbide, and graphite are predicted showing maximum concentrations in peripheral zones of the plasma.
In experiment LIP is induced in mixtures BCl3, Н2+BCl3, H2+Ar+BCl3, H2+BCl3+CH4, BF3, Н2+BF3, H2+Ar+BF3, and H2+Ar+BF3. The gases are analyzed before, during, and after laser irradiation by optical and mass spectroscopic methods. The composition of reaction products is found to be close to that predicted theoretically. The conversion of precursor gases BCl3 and BF3 into gaseous and condensed products is 100% for BCl3 and 80% for BF3. Solid deposits of up to 30 mg are obtained from all the reaction mixtures. FTIR analysis of BCl3+H2+CH4 deposits points to a presence of condensed boron and boron carbide that are also predicted by the model. Both calculations and preliminary experimental results suggest the chemical vapor deposition by LIP is promising for conversion of gaseous enriched precursors into elemental isotopes and their isotopic compounds.