M. Daub - Academia.edu (original) (raw)

Papers by M. Daub

Research paper thumbnail of Fast and reliable protein microarray production by a new drop-in-drop technique

Lab on a Chip, 2005

In contrast to DNA microarrays, production of protein microarrays is an immense technological cha... more In contrast to DNA microarrays, production of protein microarrays is an immense technological challenge due to high complexity and diversity of proteins. In this paper we investigate three essential aspects of protein microarray fabrication based on the highly parallel and non-contact TopSpot technology: evaporation of probes during long lasting production times, optimization of protein immobilization and improvement of protein microarray reproducibility. Evaporation out of the printhead reservoirs was reduced to a minimum by sealing the reservoirs with gas permeable foils or PDMS frames. This led to dramatically lowered setup times through the possibility of long-term, ready-to-print storage of filled printheads. To optimize immobilization efficiency 128 printing buffers were tested by printing two different proteins onto seven different microarray slide types. This way we were able to reduce the CV of spot diameter on the microarray slide below 1.14%. To remarkably increase protein immobilization efficiency on microarray slides the commonly used EDC-NHS system (a laboratory method for immobilization of proteins) was miniaturized by using a new drop-in-drop printing technique. Additionally the very fast UV cross-linking was used to immobilize antibodies. The optimized system was used to produce antibody microarrays and with it microarray ELISA experiments were performed successfully.

Research paper thumbnail of Non-contact production of oligonucleotide microarrays using the highly integrated TopSpot nanoliter dispenser

The Analyst, 2004

For the first time we report on the production of oligonucleotide microarrays using a highly para... more For the first time we report on the production of oligonucleotide microarrays using a highly parallel and highly integrated, pressure driven TopSpot nanoliter dispenser. The system enables non-contact printing of different media like oligonucleotides, DNA or protein solutions. We optimized the printing buffer needed for oligonucleotides microarrays production with respect to two major aspects: microfluidical optimum for droplet dispensing and biochemical coupling efficiency on different commercially available microarray slides. Coefficient of variations (CVs) of generated spot diameters were measured to be smaller than 1% within one single dispensing nozzle and smaller than 1.5% within all 24 parallel nozzles of the printhead for all printing buffers used. No carry-over and no cross-talk was found, in extensive experiments with oligonucleotides. Optimized printing buffer compositions and concentrations for oligonucleotide microarrays were found, as well as optimized coupling protocols. Furthermore, buffers and protocols were adapted to a host of different microarray slides used. With this system, prime critical points of microarray production are solved, leading to high quality high throughput microarray fabrication.

Research paper thumbnail of A Highly Parallel Nanoliter Dispenser for Microarray Fabrication

Biomedical Microdevices, 2000

We report about the correlation between satellite free droplet release and liquid viscosity in a ... more We report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies, we found that for liquids of different viscosities the duration of the pressure pulse is the predominant effect compared to pressure amplitude. This result is of essential importance when actuation parameters have to be adopted for different media like oligonucleotide, DNA or protein solutions as it is the case for the non-contact high throughput fabrication of microarrays . Experiments with oligonucleotides as well as with different proteins showed ascertained carry-over and cross-contamination free printing of DNA and protein microarrays. With it a prime critical point of microarray production is solved, leading to high quality whilst high throughput microarray fabrication. For oligonucleotides printing, we found CVs to be better than 1% within one single dispensing channel and 1.5% within all 24 channels of a 24 channel printhead for each used printing buffer. By optimizing the protein printing buffer the CVs for protein printing were reduced to about 1% within all 24 channels. As a serious practical application test oligonucleotides microarrays were produced using our nanoliter dispenser system. With it a full DNA hybridization experiment was performed. Clear positive signals one hand and no signals in the negative controls on the other hand showed that our system is suited for microarray production.

Research paper thumbnail of Pico-Injector for the Discrete Chemical Stimulation of Individual Cells with a High Temporal and Spatial Resolution

IFMBE Proceedings, 2009

ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individua... more ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individual cells in their physiological environment. Key features are the precisely controlled release of two individually addressable substances in the lower picoliter (pL) range (V = 9 pL) with a high spatial (< 50 μm) and temporal (< 100 μs) resolution while avoid any diffusion-based leakage of the drugs. This is achieved by a disposable and biocompatible cap that is placed on top of a dispenser generating a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter. For the phase-gap we have proven a long term stability of more than 30 hours against capillary priming and a maximum volume ejection rate of up to 220 nL/s.

Research paper thumbnail of Pico-Injector for the Discrete Chemical Stimulation of Individual Cells with a High Temporal and Spatial Resolution

IFMBE Proceedings, 2009

ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individua... more ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individual cells in their physiological environment. Key features are the precisely controlled release of two individually addressable substances in the lower picoliter (pL) range (V = 9 pL) with a high spatial (< 50 μm) and temporal (< 100 μs) resolution while avoid any diffusion-based leakage of the drugs. This is achieved by a disposable and biocompatible cap that is placed on top of a dispenser generating a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter. For the phase-gap we have proven a long term stability of more than 30 hours against capillary priming and a maximum volume ejection rate of up to 220 nL/s.

Research paper thumbnail of An improved 24 channel picoliter dispenser based on direct liquid displacement

TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664), 2003

For the first time we present a systematic study concerning the relation between nozzle diameter ... more For the first time we present a systematic study concerning the relation between nozzle diameter and ejected droplet volume of a highly parallel picoliter dispenser. Such dispensers are essential parts for the mass fabrication of microarrays and are able to dispense up to 96 different reagents at a pitch of 500 µm simultaneously . In contrast to an earlier design [3] we investigated different nozzle diameters. The change from 35 µm to 60 µm in nozzle diameter resulted in a doubling of dispensed volume for most used elastomers and irrespective of actuation parameters. Minimum and maximum of dispensed volumes have been determined to be 125pl and 1700 pl. Those results are based on a new design, which also includes passive microstructures for droplet homogeneity as well as modified microchannels for improved priming and prevention of cross-contamination. Based on this, the CV of droplet velocity could be reduced from 50% down to less than 5%. The CV of droplet volume is clearly below the measurement error (8%).

Research paper thumbnail of Droplet release in a highly parallel, pressure driven nanoliter dispenser

TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664), 2003

For the first time we report about the correlation between satellite free droplet release and liq... more For the first time we report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies we found that for liquids of different viscosities the length of the pressure pulse is the predominant effect compared to pressure amplitude. This result is of essential importance when actuation parameters have to be adopted for different media like oligonucleotide, DNA or protein solutions as it is the case for the non-contact highthroughput fabrication of microarrays . For each used printing buffer we found the CV to be better than 1% within one single dispensing channel and 1.5 % within all 24 channels at a pitch of 500 µm.

Research paper thumbnail of Bubble-free priming of blind channels

17th IEEE International Conference on Micro Electro Mechanical Systems. Maastricht MEMS 2004 Technical Digest, 2004

Capillary liquid transport is an enormously powerful tool and is commonly used for directing flui... more Capillary liquid transport is an enormously powerful tool and is commonly used for directing fluids without need for any external actuation. In blind channels air pockets prevent complete capillary filling, because air cannot escape out of the channel. In this paper we present for the first time a 2-level microchannel structure, which allows complete capillary filling of blind channels without

Research paper thumbnail of Integrated process control for highly parallel and contact-free microarray printing

18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005., 2005

This paper reports for the first time on an integrated process control of a highly parallel non-c... more This paper reports for the first time on an integrated process control of a highly parallel non-contact dispenser for microarray production. Monitoring the fundamental process parameters has become indispensable because of significantly increased demands on high quality microarrays. We integrated a pressure sensor in our pneumatically actuated dispenser to acquire the transient pressure pulse during droplet ejection. This enables the total process control for the dispenser and with it the adoption of operation parameters for varying liquid properties, like viscosity, surface tension and density. We optimised pressure parameter and the geometry of the actuation chamber. This made it possible to dispense liquid viscosities up to 10.8 mPas (four fold improvement) at frequencies up to 30 Hz (15 fold improvement) for all tested liquids. In addition, the integrated pressure sensor allows to detect failure modes, like flooded actuation chamber or empty printhead nozzles, leading to a higher quality of the fabricated microarrays. 0-7803-8732-5/05/$20.00

Research paper thumbnail of Bioprinting on Chip

Research paper thumbnail of Microfluidics and Beyond – Devices for Applications in Biotechnology

MRS Proceedings, 2004

For the performance of certain analytical and diagnostic tasks in modern Life Science application... more For the performance of certain analytical and diagnostic tasks in modern Life Science applications high throughput screening (HTS) methods are essential. Miniaturization, parallelization and automation allow to decrease consumption of expensive materials and lead to faster analyzing times. The miniaturization of total assay volumes by the use of microtiter plates as well as the microarray technology have revolutionized the field of biotechnology and Life Sciences. Neither printing of microarrays with droplet volumes of several picoliters, nor handling of precious enzymes in the upper nanoliter range can be accomplished with traditional liquid handling devices like air displacement pipettes. The development of novel low volume liquid handling devices, which are subject to current research, addresses the diverse requirements shifting steadily to lower volumes. Various novel non-contact dispensing methods in the nanoliter and picoliter range are presented and classified according to their working principles like air displacement and direct displacement methods (TopSpot ® , NanoJet TM , Dispensing Well Plate TM ). Properties of the various methods are compared in terms of flexibility, integration density, speed of operation, precision, addressable volume range and amenability to multi-parallel operation.

Research paper thumbnail of Turret component for a reagent vessel

Research paper thumbnail of Turret component for a reagent vessel

Research paper thumbnail of Ni nanowires electrodeposited in single ion track templates

ABSTRACT Romania c Current address: Max-Planck-Institute for Microstructure Physics, Weinberg 2, ... more ABSTRACT Romania c Current address: Max-Planck-Institute for Microstructure Physics, Weinberg 2, 06120 Halle, Germany 30-µm thick polycarbonate foils were irradiated with single swift heavy ions (e.g. Au 11.4 MeV/nucleon). After etching with solutions containing NaOH and methanol, templates containing single conical pores were obtained. The size and the shape of the nanopores depend on etching conditions such as time of etching, concentration and temperature of the etching solution. By electrochemical deposition of nickel, nanowires were grown in the single pores. The nanowires were contacted by sputtering a gold layer on top of the membrane. The magnetic measurements indicated that the nanowires possess around 1% anisotropic magnetoresistance. The current-voltage characteristic of a Ni nanowire shows a linear behavior for current densities smaller than 10 8 A/cm 2 . The maximum current density that a single Ni wire can withstand was found to be 3×10 8 A/cm 2 .

Research paper thumbnail of Reagent vessel insert and reagent vessel

Research paper thumbnail of Reagent vessel insert, reagent vessels, method for the centrifuging of at least one material and method for the pressure treatment of at least one material

Research paper thumbnail of A highly parallel picoliter dispenser with an integrated, novel capillary channel structure

Sensors and Actuators A: Physical, 2004

We present a cross-contamination free highly-parallel picoliter dispenser based on direct liquid ... more We present a cross-contamination free highly-parallel picoliter dispenser based on direct liquid displacement. Such dispensers are essential for the (mass) fabrication of microarrays [J. Ducrée, H. Gruhler, N. Hey, M. Mueller, S. Békési, M. Freygang, H. Sandmaier, R. Zengerle, TopSpot-a new method for the fabrication of microarrays, Tech. are able to dispense up to 384 different reagents at a pitch of 500 m simultaneously [A. Kuoni, M. Boillat, N.F. de Rooij, A highly parallel piezoelectric printing device for microarray technology, Tech. 88] we investigated different nozzle diameters and a novel capillary channel design. We present a systematic study concerning the relation between nozzle diameter and ejected droplet volume. The change from 35 to 60 m in nozzle diameter resulted in a doubling of dispensed volume for most used elastomers and irrespective of actuation parameters. Minimum and maximum dispensed volumes have been determined to be 125 and 1700 pl. Those results are based on a new design, which also includes passive microstructures for droplet homogeneity as well as modified microchannels for improved priming and prevention of cross-contamination. Based on this, the coefficient of variation (CV) of droplet velocity could be reduced from 50% down to less than 5%. The CV of droplet volume is clearly below the measurement error (8%).

Research paper thumbnail of Laser micromachining as a metallization tool for microfluidic polymer stacks

Journal of Micromechanics and Microengineering, 2013

Research paper thumbnail of Impact of medium properties on droplet release in a highly parallel nanoliter dispenser

Sensors and Actuators A: Physical, 2004

We report about the correlation between satellite free droplet release and liquid viscosity in a ... more We report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies we found that for liquids of different viscosities the duration of the pressure pulse is the predominant effect ...

Research paper thumbnail of Wafer-level packaging and laser bonding as an approach for silicon-into-lab-on-chip integration

Journal of Micromechanics and Microengineering, 2013

ABSTRACT A novel approach for the integration of silicon biosensors into microfluidics is present... more ABSTRACT A novel approach for the integration of silicon biosensors into microfluidics is presented. Our approach is based on wafer-level packaging of the silicon die and a laser-bonding process of the resulting mold package into a polymer-multilayer stack. The introduction of a flexible and 40 μm thin hot melt foil as an intermediate layer enables laser bonding between materials with different melting temperatures, where standard laser welding processes cannot be employed. All process steps are suitable for mass production, e.g. the approach does not involve any dispensing steps for glue or underfiller. The integration approach was demonstrated and evaluated regarding process technology by wafer-level redistribution of daisy chain silicon dies representing a generic biosensor. Electrical connection was successfully established and laser-bonding tensile strength of 5.7 N mm −2 and burst pressure of 587 kPa at a temperature of 100 °C were achieved for the new material combination. The feasibility of the complete packaging approach was shown by the fabrication of a microfluidic flow cell with embedded mold package.

Research paper thumbnail of Fast and reliable protein microarray production by a new drop-in-drop technique

Lab on a Chip, 2005

In contrast to DNA microarrays, production of protein microarrays is an immense technological cha... more In contrast to DNA microarrays, production of protein microarrays is an immense technological challenge due to high complexity and diversity of proteins. In this paper we investigate three essential aspects of protein microarray fabrication based on the highly parallel and non-contact TopSpot technology: evaporation of probes during long lasting production times, optimization of protein immobilization and improvement of protein microarray reproducibility. Evaporation out of the printhead reservoirs was reduced to a minimum by sealing the reservoirs with gas permeable foils or PDMS frames. This led to dramatically lowered setup times through the possibility of long-term, ready-to-print storage of filled printheads. To optimize immobilization efficiency 128 printing buffers were tested by printing two different proteins onto seven different microarray slide types. This way we were able to reduce the CV of spot diameter on the microarray slide below 1.14%. To remarkably increase protein immobilization efficiency on microarray slides the commonly used EDC-NHS system (a laboratory method for immobilization of proteins) was miniaturized by using a new drop-in-drop printing technique. Additionally the very fast UV cross-linking was used to immobilize antibodies. The optimized system was used to produce antibody microarrays and with it microarray ELISA experiments were performed successfully.

Research paper thumbnail of Non-contact production of oligonucleotide microarrays using the highly integrated TopSpot nanoliter dispenser

The Analyst, 2004

For the first time we report on the production of oligonucleotide microarrays using a highly para... more For the first time we report on the production of oligonucleotide microarrays using a highly parallel and highly integrated, pressure driven TopSpot nanoliter dispenser. The system enables non-contact printing of different media like oligonucleotides, DNA or protein solutions. We optimized the printing buffer needed for oligonucleotides microarrays production with respect to two major aspects: microfluidical optimum for droplet dispensing and biochemical coupling efficiency on different commercially available microarray slides. Coefficient of variations (CVs) of generated spot diameters were measured to be smaller than 1% within one single dispensing nozzle and smaller than 1.5% within all 24 parallel nozzles of the printhead for all printing buffers used. No carry-over and no cross-talk was found, in extensive experiments with oligonucleotides. Optimized printing buffer compositions and concentrations for oligonucleotide microarrays were found, as well as optimized coupling protocols. Furthermore, buffers and protocols were adapted to a host of different microarray slides used. With this system, prime critical points of microarray production are solved, leading to high quality high throughput microarray fabrication.

Research paper thumbnail of A Highly Parallel Nanoliter Dispenser for Microarray Fabrication

Biomedical Microdevices, 2000

We report about the correlation between satellite free droplet release and liquid viscosity in a ... more We report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies, we found that for liquids of different viscosities the duration of the pressure pulse is the predominant effect compared to pressure amplitude. This result is of essential importance when actuation parameters have to be adopted for different media like oligonucleotide, DNA or protein solutions as it is the case for the non-contact high throughput fabrication of microarrays . Experiments with oligonucleotides as well as with different proteins showed ascertained carry-over and cross-contamination free printing of DNA and protein microarrays. With it a prime critical point of microarray production is solved, leading to high quality whilst high throughput microarray fabrication. For oligonucleotides printing, we found CVs to be better than 1% within one single dispensing channel and 1.5% within all 24 channels of a 24 channel printhead for each used printing buffer. By optimizing the protein printing buffer the CVs for protein printing were reduced to about 1% within all 24 channels. As a serious practical application test oligonucleotides microarrays were produced using our nanoliter dispenser system. With it a full DNA hybridization experiment was performed. Clear positive signals one hand and no signals in the negative controls on the other hand showed that our system is suited for microarray production.

Research paper thumbnail of Pico-Injector for the Discrete Chemical Stimulation of Individual Cells with a High Temporal and Spatial Resolution

IFMBE Proceedings, 2009

ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individua... more ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individual cells in their physiological environment. Key features are the precisely controlled release of two individually addressable substances in the lower picoliter (pL) range (V = 9 pL) with a high spatial (< 50 μm) and temporal (< 100 μs) resolution while avoid any diffusion-based leakage of the drugs. This is achieved by a disposable and biocompatible cap that is placed on top of a dispenser generating a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter. For the phase-gap we have proven a long term stability of more than 30 hours against capillary priming and a maximum volume ejection rate of up to 220 nL/s.

Research paper thumbnail of Pico-Injector for the Discrete Chemical Stimulation of Individual Cells with a High Temporal and Spatial Resolution

IFMBE Proceedings, 2009

ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individua... more ABSTRACT We present a new tool (Pico-Injector) for the discrete chemical stimulation of individual cells in their physiological environment. Key features are the precisely controlled release of two individually addressable substances in the lower picoliter (pL) range (V = 9 pL) with a high spatial (< 50 μm) and temporal (< 100 μs) resolution while avoid any diffusion-based leakage of the drugs. This is achieved by a disposable and biocompatible cap that is placed on top of a dispenser generating a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter. For the phase-gap we have proven a long term stability of more than 30 hours against capillary priming and a maximum volume ejection rate of up to 220 nL/s.

Research paper thumbnail of An improved 24 channel picoliter dispenser based on direct liquid displacement

TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664), 2003

For the first time we present a systematic study concerning the relation between nozzle diameter ... more For the first time we present a systematic study concerning the relation between nozzle diameter and ejected droplet volume of a highly parallel picoliter dispenser. Such dispensers are essential parts for the mass fabrication of microarrays and are able to dispense up to 96 different reagents at a pitch of 500 µm simultaneously . In contrast to an earlier design [3] we investigated different nozzle diameters. The change from 35 µm to 60 µm in nozzle diameter resulted in a doubling of dispensed volume for most used elastomers and irrespective of actuation parameters. Minimum and maximum of dispensed volumes have been determined to be 125pl and 1700 pl. Those results are based on a new design, which also includes passive microstructures for droplet homogeneity as well as modified microchannels for improved priming and prevention of cross-contamination. Based on this, the CV of droplet velocity could be reduced from 50% down to less than 5%. The CV of droplet volume is clearly below the measurement error (8%).

Research paper thumbnail of Droplet release in a highly parallel, pressure driven nanoliter dispenser

TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664), 2003

For the first time we report about the correlation between satellite free droplet release and liq... more For the first time we report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies we found that for liquids of different viscosities the length of the pressure pulse is the predominant effect compared to pressure amplitude. This result is of essential importance when actuation parameters have to be adopted for different media like oligonucleotide, DNA or protein solutions as it is the case for the non-contact highthroughput fabrication of microarrays . For each used printing buffer we found the CV to be better than 1% within one single dispensing channel and 1.5 % within all 24 channels at a pitch of 500 µm.

Research paper thumbnail of Bubble-free priming of blind channels

17th IEEE International Conference on Micro Electro Mechanical Systems. Maastricht MEMS 2004 Technical Digest, 2004

Capillary liquid transport is an enormously powerful tool and is commonly used for directing flui... more Capillary liquid transport is an enormously powerful tool and is commonly used for directing fluids without need for any external actuation. In blind channels air pockets prevent complete capillary filling, because air cannot escape out of the channel. In this paper we present for the first time a 2-level microchannel structure, which allows complete capillary filling of blind channels without

Research paper thumbnail of Integrated process control for highly parallel and contact-free microarray printing

18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005., 2005

This paper reports for the first time on an integrated process control of a highly parallel non-c... more This paper reports for the first time on an integrated process control of a highly parallel non-contact dispenser for microarray production. Monitoring the fundamental process parameters has become indispensable because of significantly increased demands on high quality microarrays. We integrated a pressure sensor in our pneumatically actuated dispenser to acquire the transient pressure pulse during droplet ejection. This enables the total process control for the dispenser and with it the adoption of operation parameters for varying liquid properties, like viscosity, surface tension and density. We optimised pressure parameter and the geometry of the actuation chamber. This made it possible to dispense liquid viscosities up to 10.8 mPas (four fold improvement) at frequencies up to 30 Hz (15 fold improvement) for all tested liquids. In addition, the integrated pressure sensor allows to detect failure modes, like flooded actuation chamber or empty printhead nozzles, leading to a higher quality of the fabricated microarrays. 0-7803-8732-5/05/$20.00

Research paper thumbnail of Bioprinting on Chip

Research paper thumbnail of Microfluidics and Beyond – Devices for Applications in Biotechnology

MRS Proceedings, 2004

For the performance of certain analytical and diagnostic tasks in modern Life Science application... more For the performance of certain analytical and diagnostic tasks in modern Life Science applications high throughput screening (HTS) methods are essential. Miniaturization, parallelization and automation allow to decrease consumption of expensive materials and lead to faster analyzing times. The miniaturization of total assay volumes by the use of microtiter plates as well as the microarray technology have revolutionized the field of biotechnology and Life Sciences. Neither printing of microarrays with droplet volumes of several picoliters, nor handling of precious enzymes in the upper nanoliter range can be accomplished with traditional liquid handling devices like air displacement pipettes. The development of novel low volume liquid handling devices, which are subject to current research, addresses the diverse requirements shifting steadily to lower volumes. Various novel non-contact dispensing methods in the nanoliter and picoliter range are presented and classified according to their working principles like air displacement and direct displacement methods (TopSpot ® , NanoJet TM , Dispensing Well Plate TM ). Properties of the various methods are compared in terms of flexibility, integration density, speed of operation, precision, addressable volume range and amenability to multi-parallel operation.

Research paper thumbnail of Turret component for a reagent vessel

Research paper thumbnail of Turret component for a reagent vessel

Research paper thumbnail of Ni nanowires electrodeposited in single ion track templates

ABSTRACT Romania c Current address: Max-Planck-Institute for Microstructure Physics, Weinberg 2, ... more ABSTRACT Romania c Current address: Max-Planck-Institute for Microstructure Physics, Weinberg 2, 06120 Halle, Germany 30-µm thick polycarbonate foils were irradiated with single swift heavy ions (e.g. Au 11.4 MeV/nucleon). After etching with solutions containing NaOH and methanol, templates containing single conical pores were obtained. The size and the shape of the nanopores depend on etching conditions such as time of etching, concentration and temperature of the etching solution. By electrochemical deposition of nickel, nanowires were grown in the single pores. The nanowires were contacted by sputtering a gold layer on top of the membrane. The magnetic measurements indicated that the nanowires possess around 1% anisotropic magnetoresistance. The current-voltage characteristic of a Ni nanowire shows a linear behavior for current densities smaller than 10 8 A/cm 2 . The maximum current density that a single Ni wire can withstand was found to be 3×10 8 A/cm 2 .

Research paper thumbnail of Reagent vessel insert and reagent vessel

Research paper thumbnail of Reagent vessel insert, reagent vessels, method for the centrifuging of at least one material and method for the pressure treatment of at least one material

Research paper thumbnail of A highly parallel picoliter dispenser with an integrated, novel capillary channel structure

Sensors and Actuators A: Physical, 2004

We present a cross-contamination free highly-parallel picoliter dispenser based on direct liquid ... more We present a cross-contamination free highly-parallel picoliter dispenser based on direct liquid displacement. Such dispensers are essential for the (mass) fabrication of microarrays [J. Ducrée, H. Gruhler, N. Hey, M. Mueller, S. Békési, M. Freygang, H. Sandmaier, R. Zengerle, TopSpot-a new method for the fabrication of microarrays, Tech. are able to dispense up to 384 different reagents at a pitch of 500 m simultaneously [A. Kuoni, M. Boillat, N.F. de Rooij, A highly parallel piezoelectric printing device for microarray technology, Tech. 88] we investigated different nozzle diameters and a novel capillary channel design. We present a systematic study concerning the relation between nozzle diameter and ejected droplet volume. The change from 35 to 60 m in nozzle diameter resulted in a doubling of dispensed volume for most used elastomers and irrespective of actuation parameters. Minimum and maximum dispensed volumes have been determined to be 125 and 1700 pl. Those results are based on a new design, which also includes passive microstructures for droplet homogeneity as well as modified microchannels for improved priming and prevention of cross-contamination. Based on this, the coefficient of variation (CV) of droplet velocity could be reduced from 50% down to less than 5%. The CV of droplet volume is clearly below the measurement error (8%).

Research paper thumbnail of Laser micromachining as a metallization tool for microfluidic polymer stacks

Journal of Micromechanics and Microengineering, 2013

Research paper thumbnail of Impact of medium properties on droplet release in a highly parallel nanoliter dispenser

Sensors and Actuators A: Physical, 2004

We report about the correlation between satellite free droplet release and liquid viscosity in a ... more We report about the correlation between satellite free droplet release and liquid viscosity in a highly parallel, pressure driven nanoliter dispenser. In extensive studies we found that for liquids of different viscosities the duration of the pressure pulse is the predominant effect ...

Research paper thumbnail of Wafer-level packaging and laser bonding as an approach for silicon-into-lab-on-chip integration

Journal of Micromechanics and Microengineering, 2013

ABSTRACT A novel approach for the integration of silicon biosensors into microfluidics is present... more ABSTRACT A novel approach for the integration of silicon biosensors into microfluidics is presented. Our approach is based on wafer-level packaging of the silicon die and a laser-bonding process of the resulting mold package into a polymer-multilayer stack. The introduction of a flexible and 40 μm thin hot melt foil as an intermediate layer enables laser bonding between materials with different melting temperatures, where standard laser welding processes cannot be employed. All process steps are suitable for mass production, e.g. the approach does not involve any dispensing steps for glue or underfiller. The integration approach was demonstrated and evaluated regarding process technology by wafer-level redistribution of daisy chain silicon dies representing a generic biosensor. Electrical connection was successfully established and laser-bonding tensile strength of 5.7 N mm −2 and burst pressure of 587 kPa at a temperature of 100 °C were achieved for the new material combination. The feasibility of the complete packaging approach was shown by the fabrication of a microfluidic flow cell with embedded mold package.