Angelika Tawil

Fractional exhaled nitric oxide measurement with a handheld device.

A sensing system for fractional exhaled nitric oxide (FeNO) measurement is presented, which is characterized by a compact setup and a cost potential to be made available for the patient at home. The sensing is based on the work function measurement of a phthalocyanine-type sensing material, which is shown to be sufficiently sensitive for NO(2) in the ppb range. The transducer used to measure the work function is a field effect transistor with a suspended gate electrode. Selectivity is given with respect to other breath components including typically metabolic by-products. The measurement system includes breath treatments in a simple setup, which essentially are dehumidification and a quantitative conversion of NO to NO(2) with a conversion rate of approx. 95%, using a disposable oxidation catalyst. The accomplishment of the correct exhalation maneuver and feeding of the suited portion of exhaled air to the sensor is provided by breath sampling means. The sensor is not gas consuming. This allows us to fill the measurement chamber once, instead of establishing a gas flow for the measurement. This feature simplifies the device architecture. In this paper, we report on sensor characteristics, system architecture and measurement with artificial breath-gas as well as with human breath with the device.

Optimization of the work function response of CO 2 -sensing Polysiloxane layers by modification of the polymerization

Gas sensors based on the work function read out of (Hetero-) Polysiloxane sensing layers can be used for the detection of CO2. To investigate the reaction with CO2, different polymers based on modified Polysiloxanes are examined. It is shown that the sensitive layers can be systematically modified to evoke a preferred and specified chemical reaction with CO2. This may open up the possibility for new ambient-temperature-CO2-sensors, for which a fast response time, a high long-term stability as well as a high sensitivity between 400 ppm CO2 (background in atmosphere) and 4000 ppm CO2 (bad air) are characteristic.

Ethanol Sensing with Cu-BTC Metal Organic Framework: Mass Sensitive, Work Function Based and IR Investigations

Cu-BTC, also known as H-KUST 1, belongs to Metal Organic Frameworks (MOFs). Nanoporosity, relatively good thermal stability and unsaturated metal sites are some of its properties that make this MOF promising for application as a gas sensing material. In this work we chose different experimental approaches to examine trace gas sensing (5 to 50 ppm) of ethanol with Cu-BTC. Measurements with mass sensitive, as well as work function based readout, were successfully performed in dry synthetic air at room temperature. Strong, fast and concentration dependent response to ethanol was observed. In-situ measurements with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were additionally applied to visualize the adsorption of ethanol molecules on the Cu-BTC sensing layer.