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Freiburg, Germany

Ylli K.,Hahn Schickard | Hoffmann D.,Hahn Schickard | Willmann A.,Hahn Schickard | Folkmer B.,Hahn Schickard | And 2 more authors.
Journal of Physics: Conference Series | Year: 2015

Energy Harvesting from human motion as a means of powering body-worn devices has been in the focus of research groups for several years now. This work presents a rotational inductive energy harvester that can generate a sufficient amount of energy during normal walking to power small electronic systems. Three pendulum structures and their geometrical parameters are investigated in detail through a system model and system simulations. Based on these results a prototype device is fabricated. The masses and angles between pendulum arms can be changed for the experiments. The device is tested under real-world conditions and generates an average power of up to 23.39 mW across a resistance equal to the coil resistance of the optimal pendulum configuration. A regulated power output of the total system including power management of 3.3 mW is achieved. © Published under licence by IOP Publishing Ltd.

Butz N.,Albert Ludwigs University of Freiburg | Taschwer A.,Hahn Schickard | Manoli Y.,Albert Ludwigs University of Freiburg | Kuhl M.,Albert Ludwigs University of Freiburg
Digest of Technical Papers - IEEE International Solid-State Circuits Conference | Year: 2016

Functional electrical stimulation (FES) is a technique that stimulates nerves by electrical charge, but carries the risk of charge accumulation, voltage pile-up, electrode corrosion and finally tissue destruction. Using biphasic stimulus current pulses, the main transferred charge is compensated by reversing the current direction. However, due to PVT variations in integrated circuits mismatch in the biphasic waveform always occurs. Charge balancing (CB) has thus become an integral part of FES to ensure safe chronic stimulation [1]. © 2016 IEEE.

Moranz C.,Albert Ludwigs University of Freiburg | Ghafarian M.H.,Albert Ludwigs University of Freiburg | Ylli K.,Hahn Schickard | Manoli Y.,Albert Ludwigs University of Freiburg
Journal of Physics: Conference Series | Year: 2015

This paper presents an autonomous interface circuit which uses solar cells to automatically recharge chip integrated micro fuel cell accumulator arrays. These accumulators comprise a fuel cell for powering systems and a hydrolysis cell for charging the integrated hydrogen storage. The charging current is continuously monitored and the interface circuit automatically maximizes and controls the charging current. The solar cells powering the charging process are projected to be part of the chip package. The presented system, in combination with a previously developed voltage regulator and integrated sensors or actuators enables the implementation of fully integrated energy autonomous systems. © Published under licence by IOP Publishing Ltd.

Schwemmer F.,Albert Ludwigs University of Freiburg | Hutzenlaub T.,Hahn Schickard | Buselmeier D.,Albert Ludwigs University of Freiburg | Paust N.,Albert Ludwigs University of Freiburg | And 4 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2015

The generation of mixtures with precisely metered volumes is essential for reproducible automation of laboratory workflows. Splitting a given liquid into well-defined metered sub-volumes, the so-called aliquoting, has been frequently demonstrated on centrifugal microfluidics. However, so far no solution exists for assays that require simultaneous aliquoting of multiple, different liquids and the subsequent pairwise combination of aliquots with full fluidic separation before combination. Here, we introduce the centrifugo-pneumatic multi-liquid aliquoting designed for parallel aliquoting and pairwise combination of multiple liquids. All pumping and aliquoting steps are based on a combination of centrifugal forces and pneumatic forces. The pneumatic forces are thereby provided intrinsically by centrifugal transport of the assay liquids into dead end chambers to compress the enclosed air. As an example, we demonstrate simultaneous aliquoting of 1.) a common assay reagent into twenty 5 μl aliquots and 2.) five different sample liquids, each into four aliquots of 5 μl. Subsequently, the reagent and sample aliquots are simultaneously transported and combined into twenty collection chambers. All coefficients of variation for metered volumes were between 0.4%-1.0% for intra-run variations and 0.5%-1.2% for inter-run variations. The aliquoting structure is compatible to common assay reagents with a wide range of liquid and material properties, demonstrated here for contact angles between 20° and 60°, densities between 789 and 1855 kg m-3 and viscosities between 0.89 and 4.1 mPa s. The centrifugo-pneumatic multi-liquid aliquoting is implemented as a passive fluidic structure into a single fluidic layer. Fabrication is compatible to scalable fabrication technologies such as injection molding or thermoforming and does not require any additional fabrication steps such as hydrophilic or hydrophobic coatings or integration of active valves. © The Royal Society of Chemistry 2015.

Schuler F.,Hahn Schickard | Schuler F.,Albert Ludwigs University of Freiburg | Trotter M.,Hahn Schickard | Zengerle R.,Hahn Schickard | And 3 more authors.
Analytical Chemistry | Year: 2016

Multiplexing in polymerase chain reaction (PCR) is a technique widely used to save cost and sample material and to increase sensitivity compared to distributing a sample to several singleplex reactions. One of the most common methods to detect the different amplification products is the use of fluorogenic probes that emit at different wavelengths (colors). To reduce the number of detection channels, several methods for monochrome multiplexing have been suggested. However, they pose restrictions to the amplifiable target length, the sequence, or the melting temperature. To circumvent these limitations, we suggest a novel approach that uses different fluorophores with the same emission maximum. Discrimination is achieved by their different fluorescence stability during photobleaching. Atto488 (emitting at the same wavelength as 6-carboxyfluorescein, FAM) and Atto467N (emitting at the same wavelength as cyanine 5, Cy5) were found to bleach significantly less than FAM and Cy5; i.e., the final fluorescence of Atto dyes was more than tripled compared to FAM and Cy5. We successfully applied this method by performing a 4-plex PCR targeting antibiotic resistance genes in S. aureus using only 2 color channels. Confidence of discrimination between the targets was >99.9% at high copy initial copy numbers of 100 000 copies. Cases where both targets were present could be discriminated with equal confidence for Cy5 channel and reduced levels of confidence (>68%) for FAM channel. Moreover, a 2-plex digital PCR reaction in 1 color channel was shown. In the future, the degree of multiplexing may be increased by adding fluorogenic probe pairs with other emission wavelengths. The method may also be applied to other probe and assay formats, such as Förster resonance energy transfer (FRET) probes and immunoassays. © 2016 American Chemical Society.

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