Felix von Stetten - Academia.edu (original) (raw)

Papers by Felix von Stetten

IEEE Pervasive Computing, 2008

P ER VA SI V E computing 15

... Prototyping is organized in rapid prototyping chains for polymer fabrication, sealing and ass... more ... Prototyping is organized in rapid prototyping chains for polymer fabrication, sealing and assembly in a rapid prototyping workshop. ... of multiple fluidic components onto a single system with the ability of a well defined fabrication process to fabricate cost efficient devices. ...

Applied and Environmental Microbiology, 2006

Differentiation of the species within the genus Listeria is important for the food industry but o... more Differentiation of the species within the genus Listeria is important for the food industry but only a few reliable methods are available so far. While a number of studies have used Fourier transform infrared (FTIR) spectroscopy to identify bacteria, the extraction of complex pattern information from the infrared spectra remains difficult. Here, we apply artificial neural network technology (ANN), which is an advanced multivariate data-processing method of pattern analysis, to identify Listeria infrared spectra at the species level. A hierarchical classification system based on ANN analysis for Listeria FTIR spectra was created, based on a comprehensive reference spectral database including 243 well-defined reference strains of Listeria monocytogenes, L. innocua, L. ivanovii, L. seeligeri, and L. welshimeri. In parallel, a univariate FTIR identification model was developed. To evaluate the potentials of these models, a set of 277 isolates of diverse geographical origins, but not included in the reference database, were assembled and used as an independent external validation for species discrimination. Univariate FTIR analysis allowed the correct identification of 85.2% of all strains and of 93% of the L. monocytogenes strains. ANN-based analysis enhanced differentiation success to 96% for all Listeria species, including a success rate of 99.2% for correct L. monocytogenes identification. The identity of the 277-strain test set was also determined with the standard phenotypical API Listeria system. This kit was able to identify 88% of the test isolates and 93% of L. monocytogenes strains. These results demonstrate the high reliability and strong potential of ANN-based FTIR spectrum analysis for identification of the five Listeria species under investigation. Starting from a pure culture, this technique allows the cost-efficient and rapid identification of Listeria species within 25 h and is suitable for use in a routine food microbiological laboratory.

Journal of Microbiological Methods, 1998

The paper describes a novel PCR assay for discriminating psychrotolerant and mesophilic strains o... more The paper describes a novel PCR assay for discriminating psychrotolerant and mesophilic strains of the Bacillus cereus group by targeting of 16S rDNA signatures. Application of the assay circumvents long-term growth tests at low temperature currently used to detect psychrotolerant strains. PCR was performed with pure cultures. A 100% correlation of PCR and growth data at 78C was obtained for the 194 B. cereus group strains tested. Potential applications of the assay for the dairy industry and agriculture are suggested.

Environmental Microbiology, 1999

Bacillus weihenstephanensis strains are psychrotolerant and grow from below 78C to 388C. Closely ... more Bacillus weihenstephanensis strains are psychrotolerant and grow from below 78C to 388C. Closely related mesophilic Bacillus cereus strains can grow from above 78C to 468C. We classi®ed 1060 B. cereus group isolates from different soil samples with respect to their psychrotolerant and mesophilic genotypes by polymerase chain reaction (PCR) targeting of speci®c 16S rDNA and cold shock protein A gene signatures. In parallel, growth tests at 78C were carried out to determine the thermal phenotype. The geographic distribution of psychrotolerant and mesophilic isolates was found to depend signi®cantly on the prevalent annual average temperature. In one tropical, one temperate and two alpine habitats, the proportion of psychrotolerant cspA genotypes was found to be 0%, 45% and 86% and 98%, respectively, with the corresponding annual average temperatures being 288C, 78C, 48C and 18C. In the tropical habitat, only the mesophilic B. cereus was found, characterized by correspondence of thermal genotype and phenotype. In the alpine habitat, almost only the psychrotolerant B. weihenstephanensis was isolated. In the temperate habitat, mesophilic B. cereus and psychrotolerant B. weihenstephanensis as well as`intermediate thermal types' occurred, the latter having opposite thermal genotypes and phenotypes or opposing sets of thermal DNA signatures, characterized by the coexistence of mesophilic and psychrotolerant 16S rDNA operon copies within a single isolate. Both sugar utilization and DNA ®ngerprinting patterns revealed a high, probably non-clonal microsite diversity within the population of the temperate habitat. We interpret our observations in terms of a temperature-dependent selection regime, acting on recombining B. cereus/ B. weihenstephanensis populations in soil.

Sequences of the 16S ribosomal DNA (rDNA) from psychrotolerant and mesophilic strains of the Baci... more Sequences of the 16S ribosomal DNA (rDNA) from psychrotolerant and mesophilic strains of the Bacillus cereus group revealed signatures which were specific for these two thermal groups of bacteria. Further analysis of the genomic DNA from a wide range of food and soil isolates showed that B. cereus group strains have between 6 and 10 copies of 16S rDNA. Moreover, a number of these environmental strains have both rDNA operons with psychrotolerant signatures and rDNA operons with mesophilic signatures. The ability of these isolates to grow at low temperatures correlates with the prevalence of rDNA operons with psychrotolerant signatures, indicating specific nucleotides within the 16S rRNA to play a role in psychrotolerance.

Detection of psychrotrophic strains (those able to grow at or below 7°C) of the Bacillus cereus g... more Detection of psychrotrophic strains (those able to grow at or below 7°C) of the Bacillus cereus group (Bacillus cereus, Bacillus thuringiensis, and Bacillus mycoides) in food products is at present extremely slow with conventional microbiology. This is due to an inability to discriminate these cold-adapted strains from their mesophilic counterparts (those able to grow only above 7°C) by means other than growth at low temperature, which takes 5 to 10 days for detection. Here we report the development of a single PCR assay that, using major cold shock protein-specific primers and appropriate annealing temperatures, is capable of both rapidly identifying bacteria of the B. cereus group and discriminating between psychrotrophic and mesophilic strains. It is intended that this development help to more accurately predict the shelf life of refrigerated pasteurized food and dairy products and to reduce the incidence of food poisoning by psychrotrophic strains of the B. cereus group.

ABSTRACT We present an infrared (IR) thermocycler with closed loop temperature control for perfor... more ABSTRACT We present an infrared (IR) thermocycler with closed loop temperature control for performing fast polymerase chain reactions (PCR) in centrifugal microfluidics. It consists of an IR ring heater and an on-disk wireless temperature sensor module with a resolution of 0.1 K. The closed loop system enables to precisely control the temperature of the reagents even at varying conditions e.g. manufacturing tolerances of the polymer film disks, different locations of the cavities, ambient temperature changes. Due to the direct heating of the reagents by IR absorption we achieve fast average heating gradients of up to 4 K/s. Average cooling gradients so far are limited to 1.3 K/s. Our system is superior in terms of energy efficiency, temperature accuracy and overall reproducibility and robustness.

Microfluidics and Nanofluidics, 2011

We present a new method for aliquoting liquids on the centrifugal microfluidic platform. Aliquoti... more We present a new method for aliquoting liquids on the centrifugal microfluidic platform. Aliquoting is an essential unit operation to perform multiple parallel assays (“geometric multiplexing”) from one individual sample, such as genotyping by real-time polymerase chain reactions (PCR), or homogeneous immunoassay panels. Our method is a two-stage process with an initial metering phase and a subsequent transport phase initiated by switching a centrifugo-pneumatic valve. The method enables aliquoting liquids into completely separated reaction cavities. It includes precise metering that is independent on the volume of pre-stored reagents in the receiving cavities. It further excludes any cross-contamination between the receiving cavities. We characterized the performance for prototypes fabricated by three different technologies: micro-milling, thermoforming of foils, and injection molding. An initial volume of ~90 μl was split into 8 aliquots of 10 μl volume each plus a waste reservoir on a thermoformed foil disk resulting in a coefficient of variation (CV) of the metered volumes of 3.6%. A similar volume of ~105 μl was split into 16 aliquots of 6 μl volume each on micro-milled and injection-molded disks and the corresponding CVs were 2.8 and 2.2%, respectively. Thus, the compatibility of the novel aliquoting structure to the aforementioned prototyping and production technologies is demonstrated. Additionally, the important question of achievable volume precision of the aliquoting structure with respect to the production tolerances inherent to each of these production technologies is addressed experimentally and theoretically. The new method is amenable to low cost mass production, since it does not require any post-replication surface modifications like hydrophobic patches.

Biosensors & Bioelectronics, 2010

Direct electron transfer from carbon electrodes to adsorbed laccase (EC 1.10.3.2) from Trametes v... more Direct electron transfer from carbon electrodes to adsorbed laccase (EC 1.10.3.2) from Trametes versicolor is widely used to enable mediatorless enzymatic biofuel cell cathodes. However, data published so far are poorly comparable in terms of oxygen reduction performance. We thus present a comparative characterization of carbon-based electrode materials as cathode in half-cell configuration, employing adsorbed laccase as oxygen reduction catalyst.

Journal of Micromechanics and Microengineering, 2007

This paper reviews the centrifugal 'Bio-Disk' platform which is based on rotationally controlled,... more This paper reviews the centrifugal 'Bio-Disk' platform which is based on rotationally controlled, multi-scale liquid handling to fully integrate and automate complex analysis and synthesis protocols in the life sciences. The platform offers the crucial ingredients for a rapid development of applications: a coherent library of fluidic unit operations, a device technology for actuation, liquid interfacing and detection as well as a developer toolbox providing experimental testing, rapid prototyping and simulation capabilities. Various applications in the fields of life science, in vitro diagnostics and micro-process engineering are demonstrated.

Lab on A Chip, 2010

This critical review is motivated by an increasing interest of the microfluidics community in dev... more This critical review is motivated by an increasing interest of the microfluidics community in developing complete Lab-on-a-Chip solutions based on thin and flexible films (Lab-on-a-Foil). Those implementations benefit from a broad range of fabrication methods that are partly adopted from well-established macroscale processes or are completely new and promising. In addition, thin and flexible foils enable various features like low thermal resistance for efficient thermocycling or integration of easily deformable chambers paving the way for new means of on-chip reagent storage or fluid transport. From an economical perspective, Lab-on-a-Foil systems are characterised by low material consumption and often low-cost materials which are attractive for cost-effective high-volume fabrication of self-contained disposable chips. The first part of this review focuses on available materials, fabrication processes and approaches for integration of microfluidic functions including liquid control and transport as well as storage and release of reagents. In the second part, an analysis of the state of Lab-on-a-Foil applications is provided with a special focus on nucleic acid analysis, immunoassays, cell-based assays and home care testing. We conclude that the Lab-on-a-Foil approach is very versatile and significantly expands the toolbox for the development of Lab-on-a-Chip solutions.

We present a novel microfluidic platform using laminar-flow magnetophoresis for combined continuo... more We present a novel microfluidic platform using laminar-flow magnetophoresis for combined continuous extraction and purification of DNA. All essential unit operations (DNA binding, sample washing and DNA elution) are integrated on one single chip. The key function is the motion of magnetic beads given by the interplay of laminar flow and time-varying magnetic field. The time for extraction was 1 minute. The device is a central part of a complete biochemical system for continuous monitoring of cell-growth in bioreactors. The novel platform allows continuous purification of DNA, but is also applicable to purification of RNA, proteins or cells, including their subsequent real-time analysis in general.

We present the operational concept, microfabrication, and electrical performance of an enzyme-les... more We present the operational concept, microfabrication, and electrical performance of an enzyme-less direct glucose fuel cell for harvesting the chemical energy of glucose from body fluids. The spatial concentrations of glucose and oxygen at the electrodes of the one-compartment setup are established by self-organization, governed by the balance of electro-chemical depletion and membrane diffusion. Compared to less stable enzymatic and immunogenic microbial fuel cells, this robust approach excels with an extended life time, the amenability to sterilization and biocompatibility, showing up a clear route towards an autonomous power supply for long-term medical implants without the need of surgical replacement and external refueling. Operating in physiological phosphate buffer solution containing 0.1 wt% glucose and having a geometrical cathode area of 10 cm2, our prototype already delivers 20 µ W peak power over a period of 7 days.

Abstract: We present an abiotically catalyzed glucose fuel cell and demonstrate its application a... more Abstract: We present an abiotically catalyzed glucose fuel cell and demonstrate its application as energy harvesting power source for a cardiac pacemaker. This is enabled by an optimized DC-DC converter operating at 40% conversion efficiency, which surpasses commercial ...

This paper describes a method for the quantitative detection of biochemical binding events onto m... more This paper describes a method for the quantitative detection of biochemical binding events onto microstructured and functional surfaces on a truly single molecular level. The classic Streptavidinbiotin system is used to provide the last detection step and the binding is visualized via gold-nanoparticles in a SEM. We showed that this allows a spatial resolution down to the nanometer scale. It also allowed us to proof the spot size dependence of binding kinetics according to the theorem of Ekins in one single experiment. The method allows to analyze any binding event on a planar surface and is enabling to measure surface densities of functional groups like the amount of BSA molecules on a blocked glass surface.

Lab on A Chip, 2010

For the first time we demonstrate a self-sufficient lab-on-a-foil system for the fully automated ... more For the first time we demonstrate a self-sufficient lab-on-a-foil system for the fully automated analysis of nucleic acids which is based on the recently available isothermal recombinase polymerase amplification (RPA). The system consists of a novel, foil-based centrifugal microfluidic cartridge including prestored liquid and dry reagents, and a commercially available centrifugal analyzer for incubation at 37 C and real-time fluorescence detection. The system was characterized with an assay for the detection of the antibiotic resistance gene mecA of Staphylococcus aureus. The limit of detection was <10 copies and time-to-result was <20 min. Microfluidic unit operations comprise storage and release of liquid reagents, reconstitution of lyophilized reagents, aliquoting the sample into #30 independent reaction cavities, and mixing of reagents with the DNA samples. The foil-based cartridge was produced by blow-molding and sealed with a self-adhesive tape. The demonstrated system excels existing PCR based lab-on-a-chip platforms in terms of energy efficiency and time-to-result. Applications are suggested in the field of mobile point-of-care analysis, B-detection, or in combination with continuous monitoring systems.

We present a new microvalve that can be monolithically integrated in centrifugally driven lab-on-... more We present a new microvalve that can be monolithically integrated in centrifugally driven lab-on-achip systems. In contrast to existing operation principles that use hydrophobic patches [1], geometrically defined capillary stops [2] or siphons [3], here we present a pneumatic principle. It needs neither additional local coatings [1] nor expensive micro sized geometries . The valve is controlled by the spinning frequency and can be switched to be open when the centrifugal pressure overcomes the pneumatic pressure inside an unvented reaction cavity. We designed and characterized valves ranging in centrifugal burst pressure from 6700 Pa to 2100 Pa. Based on this valving principle we present a new structure for aliquoting of liquids. We experimentally demonstrated this by splitting 105 µL volumes into 16 aliquots with a volume CV of 3 %.

Procedia Engineering, 2010

In this paper, we propose the development of microfluidic disposables that can be processed with ... more In this paper, we propose the development of microfluidic disposables that can be processed with standard laboratory instruments. The use of prevalent processing devices could significantly reduce existing market entry barriers for lab-on-a-chip solutions and support the market uptake of microfluidic products. We demonstrate the concept with the following applications: •microfluidic chips for DNA-purification operated on a standard laboratory centrifuge

Lab on A Chip, 2010

We present a novel process flow enabling prototyping of microfluidic cartridges made out of polym... more We present a novel process flow enabling prototyping of microfluidic cartridges made out of polymer films. Its high performance is proven by implementation of a microfluidic genotyping assay testing 22 DNA samples including clinical isolates from patients infected by methicilin-resistant Staphylococcus aureus (MRSA). The microfluidic cartridges (disks) are fabricated by a novel process called microthermoforming by soft lithography (mTSL). Positive moulds are applied allowing for higher moulding precision and very easy demoulding when compared to conventional microthermoforming. High replication accuracies with geometric disk-to-disk variations of less than 1% are typical. We describe and characterise fabrication and application of microfluidic cartridges with wall thicknesses <188 mm thus enabling efficient thermocycling during real-time polymerase chain reaction (PCR). The microfluidic cartridges are designed for operation in a slightly modified commercial thermocycling instrument. This approach demonstrates new opportunities for both microfluidic developments and well-established laboratory instruments. The microfluidic protocol is controlled by centrifugal forces and divides the liquid sample parallely into independent aliquots of 9.8 ml (CV 3.4%, N ¼ 32 wells). The genotyping assays are performed with pre-stored primers and probes for real-time PCR showing a limit of detection well below 10 copies of DNA per reaction well (N ¼ 24 wells in 3 independent disks). The system was evaluated by 44 genotyping assays comprising 22 DNA samples plus duplicates in a total of 11 disks. The samples contained clinical samples of seven different genotypes of MRSA as well as positive and negative controls. The results are in excellent agreement with the reference in microtubes.

IEEE Pervasive Computing, 2008

P ER VA SI V E computing 15

... Prototyping is organized in rapid prototyping chains for polymer fabrication, sealing and ass... more ... Prototyping is organized in rapid prototyping chains for polymer fabrication, sealing and assembly in a rapid prototyping workshop. ... of multiple fluidic components onto a single system with the ability of a well defined fabrication process to fabricate cost efficient devices. ...

Applied and Environmental Microbiology, 2006

Differentiation of the species within the genus Listeria is important for the food industry but o... more Differentiation of the species within the genus Listeria is important for the food industry but only a few reliable methods are available so far. While a number of studies have used Fourier transform infrared (FTIR) spectroscopy to identify bacteria, the extraction of complex pattern information from the infrared spectra remains difficult. Here, we apply artificial neural network technology (ANN), which is an advanced multivariate data-processing method of pattern analysis, to identify Listeria infrared spectra at the species level. A hierarchical classification system based on ANN analysis for Listeria FTIR spectra was created, based on a comprehensive reference spectral database including 243 well-defined reference strains of Listeria monocytogenes, L. innocua, L. ivanovii, L. seeligeri, and L. welshimeri. In parallel, a univariate FTIR identification model was developed. To evaluate the potentials of these models, a set of 277 isolates of diverse geographical origins, but not included in the reference database, were assembled and used as an independent external validation for species discrimination. Univariate FTIR analysis allowed the correct identification of 85.2% of all strains and of 93% of the L. monocytogenes strains. ANN-based analysis enhanced differentiation success to 96% for all Listeria species, including a success rate of 99.2% for correct L. monocytogenes identification. The identity of the 277-strain test set was also determined with the standard phenotypical API Listeria system. This kit was able to identify 88% of the test isolates and 93% of L. monocytogenes strains. These results demonstrate the high reliability and strong potential of ANN-based FTIR spectrum analysis for identification of the five Listeria species under investigation. Starting from a pure culture, this technique allows the cost-efficient and rapid identification of Listeria species within 25 h and is suitable for use in a routine food microbiological laboratory.

Journal of Microbiological Methods, 1998

The paper describes a novel PCR assay for discriminating psychrotolerant and mesophilic strains o... more The paper describes a novel PCR assay for discriminating psychrotolerant and mesophilic strains of the Bacillus cereus group by targeting of 16S rDNA signatures. Application of the assay circumvents long-term growth tests at low temperature currently used to detect psychrotolerant strains. PCR was performed with pure cultures. A 100% correlation of PCR and growth data at 78C was obtained for the 194 B. cereus group strains tested. Potential applications of the assay for the dairy industry and agriculture are suggested.

Environmental Microbiology, 1999

Bacillus weihenstephanensis strains are psychrotolerant and grow from below 78C to 388C. Closely ... more Bacillus weihenstephanensis strains are psychrotolerant and grow from below 78C to 388C. Closely related mesophilic Bacillus cereus strains can grow from above 78C to 468C. We classi®ed 1060 B. cereus group isolates from different soil samples with respect to their psychrotolerant and mesophilic genotypes by polymerase chain reaction (PCR) targeting of speci®c 16S rDNA and cold shock protein A gene signatures. In parallel, growth tests at 78C were carried out to determine the thermal phenotype. The geographic distribution of psychrotolerant and mesophilic isolates was found to depend signi®cantly on the prevalent annual average temperature. In one tropical, one temperate and two alpine habitats, the proportion of psychrotolerant cspA genotypes was found to be 0%, 45% and 86% and 98%, respectively, with the corresponding annual average temperatures being 288C, 78C, 48C and 18C. In the tropical habitat, only the mesophilic B. cereus was found, characterized by correspondence of thermal genotype and phenotype. In the alpine habitat, almost only the psychrotolerant B. weihenstephanensis was isolated. In the temperate habitat, mesophilic B. cereus and psychrotolerant B. weihenstephanensis as well as`intermediate thermal types' occurred, the latter having opposite thermal genotypes and phenotypes or opposing sets of thermal DNA signatures, characterized by the coexistence of mesophilic and psychrotolerant 16S rDNA operon copies within a single isolate. Both sugar utilization and DNA ®ngerprinting patterns revealed a high, probably non-clonal microsite diversity within the population of the temperate habitat. We interpret our observations in terms of a temperature-dependent selection regime, acting on recombining B. cereus/ B. weihenstephanensis populations in soil.

Sequences of the 16S ribosomal DNA (rDNA) from psychrotolerant and mesophilic strains of the Baci... more Sequences of the 16S ribosomal DNA (rDNA) from psychrotolerant and mesophilic strains of the Bacillus cereus group revealed signatures which were specific for these two thermal groups of bacteria. Further analysis of the genomic DNA from a wide range of food and soil isolates showed that B. cereus group strains have between 6 and 10 copies of 16S rDNA. Moreover, a number of these environmental strains have both rDNA operons with psychrotolerant signatures and rDNA operons with mesophilic signatures. The ability of these isolates to grow at low temperatures correlates with the prevalence of rDNA operons with psychrotolerant signatures, indicating specific nucleotides within the 16S rRNA to play a role in psychrotolerance.

Detection of psychrotrophic strains (those able to grow at or below 7°C) of the Bacillus cereus g... more Detection of psychrotrophic strains (those able to grow at or below 7°C) of the Bacillus cereus group (Bacillus cereus, Bacillus thuringiensis, and Bacillus mycoides) in food products is at present extremely slow with conventional microbiology. This is due to an inability to discriminate these cold-adapted strains from their mesophilic counterparts (those able to grow only above 7°C) by means other than growth at low temperature, which takes 5 to 10 days for detection. Here we report the development of a single PCR assay that, using major cold shock protein-specific primers and appropriate annealing temperatures, is capable of both rapidly identifying bacteria of the B. cereus group and discriminating between psychrotrophic and mesophilic strains. It is intended that this development help to more accurately predict the shelf life of refrigerated pasteurized food and dairy products and to reduce the incidence of food poisoning by psychrotrophic strains of the B. cereus group.

ABSTRACT We present an infrared (IR) thermocycler with closed loop temperature control for perfor... more ABSTRACT We present an infrared (IR) thermocycler with closed loop temperature control for performing fast polymerase chain reactions (PCR) in centrifugal microfluidics. It consists of an IR ring heater and an on-disk wireless temperature sensor module with a resolution of 0.1 K. The closed loop system enables to precisely control the temperature of the reagents even at varying conditions e.g. manufacturing tolerances of the polymer film disks, different locations of the cavities, ambient temperature changes. Due to the direct heating of the reagents by IR absorption we achieve fast average heating gradients of up to 4 K/s. Average cooling gradients so far are limited to 1.3 K/s. Our system is superior in terms of energy efficiency, temperature accuracy and overall reproducibility and robustness.

Microfluidics and Nanofluidics, 2011

We present a new method for aliquoting liquids on the centrifugal microfluidic platform. Aliquoti... more We present a new method for aliquoting liquids on the centrifugal microfluidic platform. Aliquoting is an essential unit operation to perform multiple parallel assays (“geometric multiplexing”) from one individual sample, such as genotyping by real-time polymerase chain reactions (PCR), or homogeneous immunoassay panels. Our method is a two-stage process with an initial metering phase and a subsequent transport phase initiated by switching a centrifugo-pneumatic valve. The method enables aliquoting liquids into completely separated reaction cavities. It includes precise metering that is independent on the volume of pre-stored reagents in the receiving cavities. It further excludes any cross-contamination between the receiving cavities. We characterized the performance for prototypes fabricated by three different technologies: micro-milling, thermoforming of foils, and injection molding. An initial volume of ~90 μl was split into 8 aliquots of 10 μl volume each plus a waste reservoir on a thermoformed foil disk resulting in a coefficient of variation (CV) of the metered volumes of 3.6%. A similar volume of ~105 μl was split into 16 aliquots of 6 μl volume each on micro-milled and injection-molded disks and the corresponding CVs were 2.8 and 2.2%, respectively. Thus, the compatibility of the novel aliquoting structure to the aforementioned prototyping and production technologies is demonstrated. Additionally, the important question of achievable volume precision of the aliquoting structure with respect to the production tolerances inherent to each of these production technologies is addressed experimentally and theoretically. The new method is amenable to low cost mass production, since it does not require any post-replication surface modifications like hydrophobic patches.

Biosensors & Bioelectronics, 2010

Direct electron transfer from carbon electrodes to adsorbed laccase (EC 1.10.3.2) from Trametes v... more Direct electron transfer from carbon electrodes to adsorbed laccase (EC 1.10.3.2) from Trametes versicolor is widely used to enable mediatorless enzymatic biofuel cell cathodes. However, data published so far are poorly comparable in terms of oxygen reduction performance. We thus present a comparative characterization of carbon-based electrode materials as cathode in half-cell configuration, employing adsorbed laccase as oxygen reduction catalyst.

Journal of Micromechanics and Microengineering, 2007

This paper reviews the centrifugal 'Bio-Disk' platform which is based on rotationally controlled,... more This paper reviews the centrifugal 'Bio-Disk' platform which is based on rotationally controlled, multi-scale liquid handling to fully integrate and automate complex analysis and synthesis protocols in the life sciences. The platform offers the crucial ingredients for a rapid development of applications: a coherent library of fluidic unit operations, a device technology for actuation, liquid interfacing and detection as well as a developer toolbox providing experimental testing, rapid prototyping and simulation capabilities. Various applications in the fields of life science, in vitro diagnostics and micro-process engineering are demonstrated.

Lab on A Chip, 2010

This critical review is motivated by an increasing interest of the microfluidics community in dev... more This critical review is motivated by an increasing interest of the microfluidics community in developing complete Lab-on-a-Chip solutions based on thin and flexible films (Lab-on-a-Foil). Those implementations benefit from a broad range of fabrication methods that are partly adopted from well-established macroscale processes or are completely new and promising. In addition, thin and flexible foils enable various features like low thermal resistance for efficient thermocycling or integration of easily deformable chambers paving the way for new means of on-chip reagent storage or fluid transport. From an economical perspective, Lab-on-a-Foil systems are characterised by low material consumption and often low-cost materials which are attractive for cost-effective high-volume fabrication of self-contained disposable chips. The first part of this review focuses on available materials, fabrication processes and approaches for integration of microfluidic functions including liquid control and transport as well as storage and release of reagents. In the second part, an analysis of the state of Lab-on-a-Foil applications is provided with a special focus on nucleic acid analysis, immunoassays, cell-based assays and home care testing. We conclude that the Lab-on-a-Foil approach is very versatile and significantly expands the toolbox for the development of Lab-on-a-Chip solutions.

We present a novel microfluidic platform using laminar-flow magnetophoresis for combined continuo... more We present a novel microfluidic platform using laminar-flow magnetophoresis for combined continuous extraction and purification of DNA. All essential unit operations (DNA binding, sample washing and DNA elution) are integrated on one single chip. The key function is the motion of magnetic beads given by the interplay of laminar flow and time-varying magnetic field. The time for extraction was 1 minute. The device is a central part of a complete biochemical system for continuous monitoring of cell-growth in bioreactors. The novel platform allows continuous purification of DNA, but is also applicable to purification of RNA, proteins or cells, including their subsequent real-time analysis in general.

We present the operational concept, microfabrication, and electrical performance of an enzyme-les... more We present the operational concept, microfabrication, and electrical performance of an enzyme-less direct glucose fuel cell for harvesting the chemical energy of glucose from body fluids. The spatial concentrations of glucose and oxygen at the electrodes of the one-compartment setup are established by self-organization, governed by the balance of electro-chemical depletion and membrane diffusion. Compared to less stable enzymatic and immunogenic microbial fuel cells, this robust approach excels with an extended life time, the amenability to sterilization and biocompatibility, showing up a clear route towards an autonomous power supply for long-term medical implants without the need of surgical replacement and external refueling. Operating in physiological phosphate buffer solution containing 0.1 wt% glucose and having a geometrical cathode area of 10 cm2, our prototype already delivers 20 µ W peak power over a period of 7 days.

Abstract: We present an abiotically catalyzed glucose fuel cell and demonstrate its application a... more Abstract: We present an abiotically catalyzed glucose fuel cell and demonstrate its application as energy harvesting power source for a cardiac pacemaker. This is enabled by an optimized DC-DC converter operating at 40% conversion efficiency, which surpasses commercial ...

This paper describes a method for the quantitative detection of biochemical binding events onto m... more This paper describes a method for the quantitative detection of biochemical binding events onto microstructured and functional surfaces on a truly single molecular level. The classic Streptavidinbiotin system is used to provide the last detection step and the binding is visualized via gold-nanoparticles in a SEM. We showed that this allows a spatial resolution down to the nanometer scale. It also allowed us to proof the spot size dependence of binding kinetics according to the theorem of Ekins in one single experiment. The method allows to analyze any binding event on a planar surface and is enabling to measure surface densities of functional groups like the amount of BSA molecules on a blocked glass surface.

Lab on A Chip, 2010

For the first time we demonstrate a self-sufficient lab-on-a-foil system for the fully automated ... more For the first time we demonstrate a self-sufficient lab-on-a-foil system for the fully automated analysis of nucleic acids which is based on the recently available isothermal recombinase polymerase amplification (RPA). The system consists of a novel, foil-based centrifugal microfluidic cartridge including prestored liquid and dry reagents, and a commercially available centrifugal analyzer for incubation at 37 C and real-time fluorescence detection. The system was characterized with an assay for the detection of the antibiotic resistance gene mecA of Staphylococcus aureus. The limit of detection was <10 copies and time-to-result was <20 min. Microfluidic unit operations comprise storage and release of liquid reagents, reconstitution of lyophilized reagents, aliquoting the sample into #30 independent reaction cavities, and mixing of reagents with the DNA samples. The foil-based cartridge was produced by blow-molding and sealed with a self-adhesive tape. The demonstrated system excels existing PCR based lab-on-a-chip platforms in terms of energy efficiency and time-to-result. Applications are suggested in the field of mobile point-of-care analysis, B-detection, or in combination with continuous monitoring systems.

We present a new microvalve that can be monolithically integrated in centrifugally driven lab-on-... more We present a new microvalve that can be monolithically integrated in centrifugally driven lab-on-achip systems. In contrast to existing operation principles that use hydrophobic patches [1], geometrically defined capillary stops [2] or siphons [3], here we present a pneumatic principle. It needs neither additional local coatings [1] nor expensive micro sized geometries . The valve is controlled by the spinning frequency and can be switched to be open when the centrifugal pressure overcomes the pneumatic pressure inside an unvented reaction cavity. We designed and characterized valves ranging in centrifugal burst pressure from 6700 Pa to 2100 Pa. Based on this valving principle we present a new structure for aliquoting of liquids. We experimentally demonstrated this by splitting 105 µL volumes into 16 aliquots with a volume CV of 3 %.

Procedia Engineering, 2010

In this paper, we propose the development of microfluidic disposables that can be processed with ... more In this paper, we propose the development of microfluidic disposables that can be processed with standard laboratory instruments. The use of prevalent processing devices could significantly reduce existing market entry barriers for lab-on-a-chip solutions and support the market uptake of microfluidic products. We demonstrate the concept with the following applications: •microfluidic chips for DNA-purification operated on a standard laboratory centrifuge

Lab on A Chip, 2010

We present a novel process flow enabling prototyping of microfluidic cartridges made out of polym... more We present a novel process flow enabling prototyping of microfluidic cartridges made out of polymer films. Its high performance is proven by implementation of a microfluidic genotyping assay testing 22 DNA samples including clinical isolates from patients infected by methicilin-resistant Staphylococcus aureus (MRSA). The microfluidic cartridges (disks) are fabricated by a novel process called microthermoforming by soft lithography (mTSL). Positive moulds are applied allowing for higher moulding precision and very easy demoulding when compared to conventional microthermoforming. High replication accuracies with geometric disk-to-disk variations of less than 1% are typical. We describe and characterise fabrication and application of microfluidic cartridges with wall thicknesses <188 mm thus enabling efficient thermocycling during real-time polymerase chain reaction (PCR). The microfluidic cartridges are designed for operation in a slightly modified commercial thermocycling instrument. This approach demonstrates new opportunities for both microfluidic developments and well-established laboratory instruments. The microfluidic protocol is controlled by centrifugal forces and divides the liquid sample parallely into independent aliquots of 9.8 ml (CV 3.4%, N ¼ 32 wells). The genotyping assays are performed with pre-stored primers and probes for real-time PCR showing a limit of detection well below 10 copies of DNA per reaction well (N ¼ 24 wells in 3 independent disks). The system was evaluated by 44 genotyping assays comprising 22 DNA samples plus duplicates in a total of 11 disks. The samples contained clinical samples of seven different genotypes of MRSA as well as positive and negative controls. The results are in excellent agreement with the reference in microtubes.