Sven Achenbach

Extensive testing of populations against COVID-19 has been suggested as a game-changer quest to control the spread of this contagious disease and to avoid further disruption in our social, healthcare and economical systems. Nonetheless, testing millions of people for a new virus brings about quite a few challenges. The development of effective tests for the new coronavirus has become a worldwide task that relies on recent discoveries and lessons learned from past outbreaks. In this work, we review the most recent publications on microfluidics devices for the detection of viruses. The topics of discussion include different detection approaches, methods of signalling and fabrication techniques. Besides the miniaturization of traditional benchtop detection assays, approaches such as electrochemical analyses, field-effect transistors and resistive pulse sensors are considered. For emergency fabrication of quick test kits, the local capabilities must be evaluated, and the joint work of universities, industries, and governments seems to be an unequivocal necessity.

Deep x-ray lithography is a fabrication method for the production of microstructures with aspect ratios of up to 100 in up to several millimeter thick resist layers. Usually, poly(methylmethacrylate) is used as the resist layer. We have measured the molecular weight and developing rates of crosslinked and noncrosslinked PMMA foils at different GG developer temperatures for dose values between 0.1 and 8 kJ/cm3. The determined developing rates cover a region of 7 orders of magnitude: With decreasing temperature the contrast of the resist-developer system and the limit of the developing dose are increased. Crosslinked PMMA has a higher contrast compared to noncrosslinked material. These effects lead to an enhanced quality of microstructures, which is demonstrated by the grating of the LIGA microspectrometer.

Offshore wind farms built at a long distance from the onshore grid are connected via HVDC-transmission. Future HVDC-systems may connect offshore wind farms via uncontrolled diode rectifiers instead of VSC-HVDC converters. Due to this wind turbine inverters must own a grid forming capability. This paper describes a control strategy that requires only minor changes in the conventional wind turbine inverter control software to form the AC-voltage in the offshore island grid. It is shown that this strategy allows an interconnection of different wind turbine types considering auxiliary power supply and reactive power sharing.