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Strain : the journal of the British Society for Strain Measurement 12387 (2021). doi:10.1111/str.12387, Published by Wiley- Blackwell, Oxford [u.a.]

Energy Harvesting and Systems 4(3), 137-141 (2017). doi:10.1515/ehs-2017-0004, Published by De Gruyter, Berlin ; Boston, Mass.

Microsystem technologies (2020). doi:10.1007/s00542-020-04818-5, Published by Springer, Berlin

Journal of magnetism and magnetic materials : MMM 506, 166694 (2020). doi:10.1016/j.jmmm.2020.166694, Published by North-Holland Publ. Co., Amsterdam

Microsystem technologies (2020). doi:10.1007/s00542-020-04834-5, Published by Springer, Berlin

Calcification is a pathological accumulation of calcium phosphate in soft tissues including blood vessels [1] where it can cause cardiovascular morbidity and mortality e.g. heart attack [2] . Mixing blood serum with supersaturated calcium and phosphate results in colloidal calcium protein particles (CPPs) undergoing a typical ripening process. The conversion time can be optically determined by light scatter measurements of smaller primary and larger secondary CPPs (Fig 1). The half-maximal conversion time T 50 is a measure of the calcification risk in the patient. Here we report the miniaturization of the experimental setup on a polymer microchip fabricated by ultrasonic processing. Compared to the usual measurement of light scatter in a nephelometer, the analysis was accelerated by increasing the temperature. Furthermore, better reproducible results were obtained by using a staggered herringbone mixer to mix the reactants [3] . A Peltier element is employed to heat the chip. Using this setup, the analysis was shortened to 16.1 ± 1.1 min compared to 279 ± 9 min obtained in a nephelometer by increasing the temperature from 38 °C to 52 °C (Fig. 4).

Current directions in biomedical engineering 4(1), 367-370 (2018). doi:10.1515/cdbme-2018-0088, Published by De Gruyter, Berlin

Ultrasonic fabrication of fiber reinforced plastics made from thermoplastic polymer films and carbon or glass fibers enables cycle times of a few seconds and requires investment costs of only some 10,000 &euro, Besides this, the raw materials can be stored at room temperature. A fiber content of 33 vol % and a tensile strength of approximately 1.2 GPa have been achieved by ultrasonic welding of nine layers of foils from polyamide, each 100 &micro, m in thickness, and eight layers of carbon fibers, each 100 &micro, m in thickness, in between. Besides unidirectional carbon fiber reinforced polymer composite (CFRP) samples, multi-directional CFRP plates, 116 mm, 64 mm and 1.2 mm in length, width and thickness respectively, were fabricated by processing three layers of carbon fiber canvas, each 300 &micro, m in thickness, and eight layers of polyamide foils, each 100 &micro, m in thickness. Furthermore, both the discontinuous and the continuous ultrasonic fabrication processes are described and the results are presented in this paper. Large-scale production still needs to be demonstrated.

Ultrasonic hot embossing has been developed in recent years enabling quick and flexible fabrication of micro structures from thermoplastic polymers. This paper describes many possibilities of the fabrication, use, and limits of tools for this process. Tools have been produced by milling, drilling, silicon etching, photo and X-ray lithography, and electroplating and by combining these processes.

Vortex whistles generate a tone with a frequency which is a monotonically increasing function of the flow rate. This effect can be employed for flow sensors which do not need any lead-through into the fluidic channel because the frequency can be measured outside with a microphone. Flow measurements with vortex whistles can be performed both with gases and liquids. For comparatively small flow velocities the frequency is proportional to volume flow and only a weak function of temperature and fluid properties. The investigations presented here show that at high flow rates the frequency increases with the density of the gas. Micro whistles designed similar to organ pipes were also investigated. However their frequency is not proportional to flow velocity but is bowed similar as a root function. Therefore it is not very sensitive as vortex whistle at larger flow rates.

A polyvinylidene fluoride (PVDF) micro-sensor channel with integrated gold wires was developed and manufactured by ultrasonic hot embossing and welding. The sensor channel was employed to detect the slug length distribution in a liquid–liquid Taylor-flow by conductivity measurements. The sensor channel was also tested regarding its usability for the detection of blockages by hot wire anemometry.

Background Small-scale micro-bioreactors have become the cultivation vessel of choice during the first steps of bioprocess development. They combine high cultivation throughput with enhanced cost efficiency per cultivation. To gain the most possible information in the early phases of process development, online monitoring of important process parameters is highly advantageous. One of these important process parameters is the oxygen transfer rate (OTR). Measurement of the OTR, however, is only available for small-scale fermentations in shake flasks via the established RAMOS technology until now. A microtiter plate-based (MTP) μRAMOS device would enable significantly increased cultivation throughput and reduced resource consumption. Still, the requirements of miniaturization for valve and sensor solutions have prevented this transfer so far. This study reports the successful transfer of the established RAMOS technology from shake flasks to 48-well microtiter plates. The introduced μRAMOS device was validated by means of one bacterial, one plant cell suspension culture and two yeast cultures. Results A technical solution for the required miniaturized valve and sensor implementation for an MTP-based μRAMOS device is presented. A microfluidic cover contains in total 96 pneumatic valves and 48 optical fibers, providing two valves and one optical fiber for each well. To reduce costs, an optical multiplexer for eight oxygen measuring instruments and 48 optical fibers is introduced. This configuration still provides a reasonable number of measurements per time and well. The well-to-well deviation is investigated by 48 identical Escherichia coli cultivations showing standard deviations comparable to those of the shake flask RAMOS system. The yeast Hansenula polymorpha and parsley suspension culture were also investigated. Conclusions The introduced MTP-based μRAMOS device enables a sound and well resolved OTR monitoring for fast- and slow-growing organisms. It offers a quality similar to standard RAMOS in OTR determination combined with an easier handling. The experimental throughput is increased 6-fold and the media consumption per cultivation is decreased roughly 12.5-fold compared to the established eight shake flask RAMOS device. Electronic supplementary material The online version of this article (doi:10.1186/s13036-016-0034-3) contains supplementary material, which is available to authorized users.

Filamentary polymer sensors with predetermined breaking points have been developed. These sensors are produced by radial micro patterning of conductive polymer filaments by ultrasonic hot embossing. Micro structures in the filaments are generated by this fabrication process in less than a second. The dimensions of radial micro grooves in a filament tune the strain at which the filament breaks. This way, overload sensors for ropes or fuses can be realized. For example the discard status or the residual life time of ropes can be controlled with a simple measurement of the electric resistance of sensor filaments. By using different sensors in one rope it is possible to indicate different load cases of the rope.

A flow parallel wire (FPW) with a center tap is used in a sensor for measuring the time of flow. A heater is placed upstream of the sensor. The upstream and downstream parts of the FPW are combined to a half bridge resulting in a large output peak when a heat pulse passes the FPW. The time between generating the heat pulse and recording the peak maximum is insensitive to the properties of the fluid.

An acceleration sensor from polymer has been developed which balances a proof mass by magnetic forces. The sen- sor is fabricated from a polyimide membrane with conductor paths from gold patterned by photolithography and etch- ing, a frame manufactured by ultrasonic hot embossing, and permanent magnets fixed to the frame. All components are assembled on a planar substrate and then the frame is kinked forming the desired three-dimensional structure.

A system of 96 micro valves has been developed and mounted on top of a 48-well micro titer plate providing two valves for each well controlling its air inlet and outlet. Testing of the valve system showed that all valves are working and are opened and closed reliably. A pneumatic system is switching inlet and outlet valves independently of each other. The geometry of the feed channels ensures an equal air flow through all wells, when the valves are open. Between the micro valves, one optical fibre was inserted through the lid of each well allowing measuring the oxygen partial pressure in the enclosed air volume by fluorescence sensor spots. Escherichia coli bacteria were grown inside the wells and their metabolism was observed by the oxygen partial pressure change due to respiration. In all 48 wells, the same oxygen transfer rate was observed within an averaged standard deviation of 1 mmol/L/h. The oxygen transfer rate differences compared to a macroscopic standard shake flask system were overall compatible within their uncertainties.

Micromachines 3(2), 325-330 (2012). doi:10.18154/RWTH-CONV-070572 special issue: "Micro Flow Controllers", Published by MDPI, Basel

A method has been developed allowing fabrication of electronic boards from flexible polymer film by ultrasonic embossing and welding within seconds. A commercially available ultrasonic welding machine and micro patterned tools from aluminum are employed first to generate conductor paths on a flexible polymer film, in a further step, surface mounted devices are assembled and fixed on the flexible polymer film by a lid, and meanwhile electrical connected via a z axis conductive tape, both the molding of the lid and the bonding between the lid and electronic boards are implemented on an ultrasonic welding machine. Finally, the effectiveness of electrical interconnection is investigated at elevated temperature, humidity and bending load, exemplified by three simple circuit boards assembled with light-emitting diodes and resistors and capacitor separately, and the experimental results show that the electrical interconnection is effective, stable, and durable.\ud