No abstract

Fine dust measurements are only conducted at few locations in our daily environment, although it is getting clearer that fine dust poses a high risk on human health. A reason for this deficit is the lack of suitable measurement systems, especially for indoor environments. Of special interest are particles with critical dimension smaller than 10 μm. They constitute the highest risk to human health as they are not filtered out by the respiratory system. By miniaturizing particle detector concepts point-of-care applications are rendered possible and production costs can be greatly reduced with microsystem fabrication technologies. The pursued detector principle is based on the interaction of single particles with electric fields. The field is created within a micro-aperture machined in a silicon substrate. Two electrodes are deposited near the aperture and form a capacitive setup. An air flow drives particles through this aperture one by one. Passing particles distort the electric field, and their presence is detected by an impedance measurement. The changes induced by a single particle are tiny and require precise measurement circuits. Our contribution presents the design of a hybrid particle detector: The sensing element consists of an array of these micro apertures with lead-outs to a measurement circuit. This element is mounted on a LTCC module, which provides all necessary electrical and fluidic functions to operate the particle detector within a larger sensor platform. Sensitive parts of the measurement circuit are mounted on the LTCC module and positioned closely to the sensing elements. Microfluidic channels guide the air flow from the sensor platform to the micro-aperture and back. Therefore, the hybrid module is both: a ceramic interconnect and a ceramic microsystem.

Low-temperature co-fired ceramics (LTCC) enable the fabrication of microfluidic elements such as channels and embedded cavities in electrical devices. Hence, LTCC facilitate the realization of complex and integrated microfluidic devices. Examples can be applied in many areas like reaction chambers for synthesis of chemical compounds. However, for many applications it is necessary to have an optically transparent interface to the surroundings. The integration of optical windows in LTCC opens up a wide field of new and innovative applications such as the observation of chemiluminescent reactions. These chemical reactions emit electromagnetic radiation and thus offer a method for noninvasive detection. Thin glasses ( 500 lm) were bonded by thermocompression onto a LTCC substrate. As the bonding agent, a glass frit paste was used. Borosilicate glasses, fused silica as well as silicon were successfully bonded onto LTCC. To join materials with a large coefficient of thermal expansion mismatch (i.e., fused silica and LTCC), it is necessary to limit the heat input to the bond interface. Therefore, a heating structure was integrated into the LTCC substrate beneath the bond interface. This bonding process provides a gas-tight optical port with a high bond strength. † Present address:

The measurement of nitrogen monoxide (NO) concentration levels is an integral part of the elemental analysis. The chemiluminescent reaction with ozone in the gas phase is a well established method for the measurement of atmospheric concentration levels in the range from 4 ppb up to 100 ppm. In this contribution we present the design of a so called micro total analytical system for NO measurements designed in ceramic. Low temperature co-fired ceramics have proven to be the ideal technology, since they offer high chemical and thermal stability as well as a high degree of freedom of design. The microfluidic system consists of three components: a dielectric barrier discharge device creating ozone, a reaction chamber with a glass window for collecting the emitted radiation, and an exhaust gas treatment consisting of a heated Pt catalyst structure. The contribution focuses on a dielectric barrier for the ozone generator capable of withstanding 600 h of continuous operation, a manufacturing method for gas tight and vacuum proof sealing of cavities, and experimental results utilizing a Pt conductor paste as a catalyst. *thomas.geiling@tu-ilmenau.de