Claas Mueller

Interferometric label-free biomolecular detection system

This work presents a simple evanescent wave sensing system based on an interferometric approach, suitable to meet the requirements of label-free sensor systems for detecting biomolecular interactions. It represents a basic concept towards label-free detection systems in various applications. The basic objectives of transducers for evanescent wave sensing are discussed. An optical detection system based on a interferometric approach using Youngs double slit configuration is discussed, set-up and characterized. With refractometric measurements of various sucrose dilutions, the performance of the pure optical set-up is evaluated. A mean resolution of the effective refractive index of without averaging was obtained and a reproducibility below σr(neff) = 0.1 × 10−6 was achieved. Furthermore basic experiments were carried out, for proofing the concepts suitability as a highly sensitive biosensor by detecting the hybridization of 21-mer DNA with an immobilized counterpart on the surface.

Low Cost Production of Disposable Microfluidics by Blister Packaging Technology

Large scale production of disposable microfluidics mostly is accomplished by injection moulding techniques today. A cost effective alternative to injection moulding might be vacuum thermoforming of polymer films. Vacuum thermoforming is the basis for medical and pharmaceutical packaging such as pharmaceutical blister packs. It allows for cheap and reliable forming of polymer films and thus seems suitable for the fabrication of disposables. Our goal is to investigate and demonstrate the potential of vacuum thermoforming for the fabrication of microtechnology components. For this purpose we have developed a simple low cost process allowing for the fabrication of disposable microfluidics by vacuum thermoforming.

Rapid processing of replication tools with high-aspect-ratio microchannels for microfluidics

Microfluidic devices are mainly used within the life sciences or chemical analysis. Polymers are ideally suited for these applications due to their physical and chemical properties. In this report, we describe a rapid low cost processing technology to fabricate mold inserts for microfluidic structures with high aspect ratio, as well as excellent surface quality and high hardness. These tools are used for hot embossing and as mold inserts for injection molding. They enable cost effective structuring of technical polymers like polycarbonate or cycloolefin copolymer. The main advantage of our approach is the availability of the geometry and the specific target material right from the start of the evaluation process of microfluidic devices. The process described enables a rapid prototyping for the development and evaluation of different microfluidic devices, and they can be used for a low-cost mass production of micro structured parts.

Innovative polymer‐based shaft instruments for minimally invasive surgery

Minimally invasive surgery (MIS) has become an important field in the health care sector over the last decade. Still, there is the need for improving existing instruments and developing new tools providing increased functionality. This work presents innovative solutions and experimental results for a new generation of innovative polymer‐based shaft instruments for minimally invasive surgery. The investigated components comprise a new kind of end‐effector mechanism and an improved force transmission for actuating the effector. The new end‐effectors consist of few discrete parts. They combine the advantages of compliant joints with those of conventional hinges (“hybrid effector”). The simple configuration will be advantageous during sterilization and, furthermore, is suitable for large‐scale production by polymer technology. The effectors show low friction and low backlash properties and therefore high functionality. In addition to that we have developed a new kind of sensitive hydraulic force transmission which may replace the force transmission by push rods of conventional shaft instruments. The hydraulic force transmission is based on leakage‐free embedding of the hydraulic fluid in modified polymer tubing. This specific hydraulic transmission component provides high efficiency force transmission and can be entirely fabricated by polymers. Both newly developed solutions reveal an increased functionality and due to their simple configuration can be manufactured by polymer technology, e.g. injection moulding. They show the potential for large‐scale production of a new class of polymer‐based shaft instruments for minimally invasive surgery.

Analyzing the Electrical Pulses Occurring during EDM of Non-Conductive Si3N4 Ceramics

With the help of an Assisting Electrode (AE), non-conductive ceramics can be machined using Electrical Discharge Machining (EDM) process. The AE helps start the EDM process and the intrinsic conductive layer (ICL) ensures that the electrical contact between the workpiece and the generator is maintained. However, the understanding of EDM process of non-conductive ceramics is limited due to the typical characteristic of the process: the geometric dimension of the discharge region is limited to few micrometers and the duration of the dielectric discharge is in the range of few microseconds making it difficult to directly observe the spark and the associated crater formation phenomenon. Analyzing the electrical signals during the EDM process could provide an insight of the process. This paper presents a study on analyzing the electric pulses occurring during the EDM process of a conductive workpiece (copper) and a non-conductive workpiece (Si3N4 ceramics). Typical pulses occurring during the EDM of a metal and a non-conductive ceramics are identified with the signal recorded at a sampling rate of 2.5 GS/s. Sampling rate of 25 MS/s is used to monitor the pulses occurring while machining a hole with depth of 1 mm. The pulses during EDM of non-conductive materials are significantly different than those during EDM of metals. Four most outstanding differences have been identified in terms of the ringing behavior of the voltage signal, the recharge time required to reach the set value of open voltage, the presence of the reverse current and the value of the peak current detected in case of Si3N4. The pulses monitored with lower sampling frequency was characterized and discriminated into sparks, arcs and short circuits. The percentage of the discriminated pulses for varying machining depth of the test structure has been presented.

Multimode interference structures as sensing elements integrated into Mach-Zehnder interferometers in polymer foils

Integrated Mach-Zehnder interferometers (MZIs) based on flexible polymer materials have been demonstrated as evanescent field sensors for the detection of refractive indices and molecule concentrations. The used application of a measurement window in classical MZIs is difficult in a roll-to-roll fabrication process. We have previously demonstrated foil-based asymmetric MZIs with different widths in sensing and reference arm which do not need a measurement window. Here we present the use of a multimode interference structure (MMI) inserted into the sensing arm of the interferometer to increase the sensitivity. We consider the expected interference signal from numerical simulations and optimize the system in terms of sensitivity, dimensions and absorption losses. The fabricated MMI-MZI foils are tested experimentally to demonstrate the function of the MMI-MZI system by applying water/glucose solutions with different refractive indices.

A Millimeter Scale Reactor Integrated PEM Fuel Cell Energy System with an On-Board Hydrogen Production, Storage and Regulation Unit for Autonomous Small Scale Applications

We present a millimeter scale reactor integrated PEM fuel cell energy source with an onboard hydrogen production reactor (realized by alkaline chemical hydride), and passive hydrogen buffering unit (realized by metal hydride) of hydrogen. A stacked system of reactor-hydrogen buffer-PEM fuel cell is demonstrated. The system is driven by the hydrolysis of the alkaline chemical hydride (NaOH+NaBH4) in the presence of micro porous catalyst layer (platinum catalyst (Ni-Pt)). The produced hydrogen gas from the reactor is buffered through the hydrogen buffer (Palladium metal hydride) and gets distributed (due to the pressure difference) onto the anode of the PEM fuel cell. The operational behaviour of the complete system is investigated with the hydrogen produced from the alkaline chemical hydride and pure hydrogen gas. Long term voltage measurements under a defined electrical load of the alkaline chemical hydride driven system was measured. The increase in time for the hydrogen production observed in the long term voltage measurement is anticipated to the degradation of the Ni-Pt catalyst. The system is “self-buffering” in nature so any change in electrical load can be handled during system operation.

Advanced Hydrogen Storage Technique to Improve the Run Time of the “Chip Integrated Micro PEM Fuel Cell System”

In this work, we present the design, fabrication and characterization of increased hydrogen storage capacity of the silicon based Chip Integrated Micro Polymer electrolyte membrane Fuel Cell Systems (CIµ-PFCS), to increase the run time. The increased hydrogen storage capacity is realized from the backside of the silicon wafer and filling (casting process) it with a newly developed advanced hydrogen storage material, palladium - polymer composite. The functionality, current-time measurements, hydrogen charging capacity and charging behaviour of the newly developed hydrogen storage technique in the CIµ-PFCS are investigated and presented in this work. The developed CIµ-PFCS with increased hydrogen storage capacity and advanced hydrogen storage technique shows a factor of 4 increased run time than the state-off-the-art CIµ-PFCS. The power density of the developed CIµ-PFCS was measured to be 2.1 [mW/cm²]. After a number of charging and discharging cycles of CIµ-PFCs with the presented hydrogen storage materials, proved to be long term stable. The advantage of the presented CIµ-PFCS is that there is an increased hydrogen storage volume on board and easy to fabricate with existing microsystem technologies.