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Dive into the research topics where Christian Karnutsch is active.

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Featured researches published by Christian Karnutsch.


Applied Optics | 2012

Design of an optofluidic biosensor using the slow-light effect in photonic crystal structures

F. Hosseinibalam; S. Hassanzadeh; A. Ebnali-Heidari; Christian Karnutsch

The authors propose a biosensor architecture based on the selective infiltration of photonic crystal (PhC) structures. The proposed sensor consists of a ring cavity coupled to an optofluidic slow-light waveguide in a PhC platform. A high potential sensitivity of 293 nm/refractive index unit is numerically demonstrated, while maintaining an ultracompact footprint.


Biomicrofluidics | 2015

Microfluidic platform for separation and extraction of plasma from whole blood using dielectrophoresis

Crispin Szydzik; Khashayar Khoshmanesh; Arnan Mitchell; Christian Karnutsch

Microfluidic based blood plasma extraction is a fundamental necessity that will facilitate many future lab-on-a-chip based point-of-care diagnostic systems. However, current approaches for providing this analyte are hampered by the requirement to provide external pumping or dilution of blood, which result in low effective yield, lower concentration of target constituents, and complicated functionality. This paper presents a capillary-driven, dielectrophoresis-enabled microfluidic system capable of separating and extracting cell-free plasma from small amounts of whole human blood. This process takes place directly on-chip, and without the requirement of dilution, thus eliminating the prerequisite of pre-processed blood samples and external liquid handling systems. The microfluidic chip takes advantage of a capillary pump for driving whole blood through the main channel and a cross flow filtration system for extracting plasma from whole blood. This filter is actively unblocked through negative dielectrophoresis forces, dramatically enhancing the volume of extracted plasma. Experiments using whole human blood yield volumes of around 180 nl of cell-free, undiluted plasma. We believe that implementation of various integrated biosensing techniques into this plasma extraction system could enable multiplexed detection of various biomarkers.


Journal of Micromechanics and Microengineering | 2016

Bonding of SU-8 films onto KMPR structures for microfluidic, air-suspended photonic and optofluidic applications

Christoph Prokop; Steffen Schoenhardt; Tanveer Mahmud; Arnan Mitchell; Christian Karnutsch

We present a method to bond unstructured and structured SU-8 films down to sub-micron thicknesses onto microchannels fabricated in KMPR using a flexible polydimethylsiloxane (PDMS) stamp. By exploiting differently casted PDMS stamps, 3D microfluidic channel networks, air-suspended photonic devices and optofluidic structures have been fabricated. First, microchannels of KMPR are patterned by photolithography and an SU-8 film is spin coated onto a prepared PDMS stamp. The stamp is then placed on top of the KMPR microchannels and the SU-8 layer is cross-linked by applying sufficient heat and pressure. After peeling off the PDMS stamp, the SU-8 layer remains bonded on the KMPR. In our experiments, we demonstrate the bonding of approximately 0.5 μm thick structured SU-8 films onto KMPR microchannels of about 500 μm width and 25 μm height. Bond strength tests demonstrated that such thin layers can withstand pressures up to 1100 hPa. The laminated SU-8 layers can enable various functionalities, e.g. sealing of microfluidic channels, realization of air-suspended photonic structures or optofluidic devices. Most importantly, the combination of fluid handling in the microchannels and air-suspended photonic structures realized in the laminated SU-8 layer enables research towards a large range of applications, such as optofluidics, biosensors, chemical and biomedical analysis, environmental investigations, and renewable energy.


Journal of Lightwave Technology | 2015

A Proposal for Loss Engineering in Slow-Light Photonic Crystal Waveguides

Aliakbar Ebnali-Heidari; Christoph Prokop; Majid Ebnali-Heidari; Christian Karnutsch

The authors present a loss engineering method for slow-light photonic crystal (PhC) waveguides. Our proposed method for engineering the loss is based on optofluidic techniques to produce low propagation loss in the low dispersions slow-light regime. We numerically demonstrate that this approach allows one to control the propagation loss (from 180 to 120 dB/cm) by selective infiltration of suitable fluids into air holes of a PhC waveguide around the group velocity of c/55 to c/70. It is proposed that fabrication imperfections, i.e., roughness and other deviations from an ideal structure that lead to propagation losses, can be compensated by a selective nanoinfiltration method. A loss of 150 dB/cm for loss-engineered waveguides, compared to 230 dB/cm for conventional waveguides, is numerically demonstrated, while both waveguide structures maintain the same group index-bandwidth product.


Journal of Lightwave Technology | 2016

Air-Suspended SU-8 Polymer Waveguide Grating Couplers

Christoph Prokop; Steffen Schoenhardt; Bert Laegel; Sandra Wolff; Arnan Mitchell; Christian Karnutsch

We present SU-8 polymer waveguide grating couplers for TE mode with enhanced refractive index contrast by employing air as upper and lower cladding layer. Numerical simulations predict a coupling loss of 4.9 dB, indicating a coupling efficiency of 32% at a maximum spectral response of 1550 nm. Based on a polymer lamination method, air-suspended waveguide grating couplers were successfully fabricated and characterized. Due to current limitations in the fabrication process, the perturbation of the experimental grating couplers is weaker than the original simulation. However, transmission measurements have shown that a single grating coupler exhibits approximately 8 dB coupling loss at a center wavelength of 1557 nm, indicating a coupling efficiency of 16% with respect to a single-mode optical fiber. The demonstrated parallel fabrication method employing the widely used SU-8 photoresist makes the polymer waveguide grating couplers very attractive for a wide range of low-cost polymer photonic applications.


Proceedings of SPIE | 2015

Air-suspended polymer rib waveguides

Christoph Prokop; Philipp Kleeßen; Nico Irmler; Arnan Mitchell; Christian Karnutsch

In order to achieve a high refractive index contrast for air-suspended photonic devices, we present a method for laminating thin polymer films onto structured polymer layers that exhibit an air cavity. By using a flat PDMS stamp, polymer films can be transferred over areas of several hundred square microns. On top of the air-suspended slab a second layer of photoresist can be spun and subsequently every desired photonic structure can be defined by using standard photolithography. Here, to demonstrate the feasibility of our lamination method for polymer photonic devices, we present optical modeling and experimental results of air-suspended single mode rib waveguides. Waveguiding is shown for visible and infrared light and a beam profile for λ = 1550 nm is presented that underpins single mode behavior of the rib waveguide.


Optical Engineering | 2017

Tunable air-suspended polymer grating couplers

Christoph Prokop; Tobias Schmalz; Philipp Kleessen; Bert Laegel; Sandra Wolff; Arnan Mitchell; Christian Karnutsch

Abstract. We present thermal tuning of air-suspended SU-8 polymer waveguide grating couplers for TE-polarized light. Numerical simulations have been performed to estimate the wavelength shift caused by the change of temperature. Due to the small positive thermal expansion and large negative thermo-optic coefficient of SU-8, a shift toward shorter wavelengths is expected. In the experimental evaluation, a negative wavelength shift from 1542 nm at 20°C toward 1527 nm at 56°C is obtained with approximately −0.42  nm K−1 matching the theoretical considerations.


Optofluidics, Microfluidics and Nanofluidics | 2016

Selective infiltration and storage of picoliter volumes of liquids into sealed SU-8 microwells

Christoph Prokop; Tobias Schmalz; Christian Karnutsch

Abstract This paper describes the selective infiltration and storage of picoliter volumes of water and IPA in arrays of sealed SU-8 microwells. Microwells, with a volume of approximately 300 picoliters, are fabricated employing photolithography and a polymer onto polymer lamination method to seal the structures with a thin cover of SU-8 and PDMS in order to suppress the evaporation of the infiltrated liquids. A glass capillary is used to punch through the SU-8/PDMS cover and to infiltrate the liquid of interest into the microwells. The influence of the mixing ratio of the PDMS and its curing agent is studied and the results show that a lower ratio of 2:1 suppresses the evaporation more when compared to the standard mixing ratio of 10:1. In regards to water and IPA, the dwell time in the reservoirs was increased by approximately 50 % and 450 % respectively. Depending on the physical properties of the microwells and the liquids, the SU-8/PDMS cover suppresses the evaporation up to 32 mins for water and 463 mins for IPA, respectively, until the microwell is completely empty again. Additionally, multiple infiltrations of the same microwell are demonstrated using two immiscible liquids IPA and paraffin oil. Based on the popular polymers SU-8 and PDMS, the sealed microwell structures are scalable and combinable with different glass capillaries according to the needs of future analytical research and medical diagnostics.


Optofluidics, Microfluidics and Nanofluidics | 2015

BANSAI - An optofluidic approach for biomedical analysis

Markus Knoerzer; Christoph Prokop; Graciete M. Rodrigues Ribeiro; Horst Mayer; Jens Brümmer; Arnan Mitchell; Dominik G. Rabus; Christian Karnutsch

Abstract Lab-on-a-chip based portable blood analysis systems would allow point-of-care measurements, e.g. in an ambulance, or in remote areas with no fast access to medical care. Such a systemwould provide much faster information about the health of a patient. Here,we present a system that is based on absorption spectroscopy and uses an organic laser, which is tunable in the visible range. The feasibility of the system is shown with a table-top setup using laboratory equipment. Measurements of human albumin show linear behaviour in a range from 2.5 g/L to 60 g/L. In a consecutive setup the system is implemented on a microfluidic chip and is capable of measuring simultaneously transmitted and side scattered intensities, even with ambient light present. Air-suspended grating couplers on polymers are shown as the first element of a lab-on-a-chip implementation.


european quantum electronics conference | 2011

Improved lasing action from dye doped SU8 films exploiting biologically derived nanostructures

Dingke Zhang; Gorgi Kostovski; Christian Karnutsch; Arnan Mitchell

Photonic structures found in biological organisms are often startling in their complexity and surprising in their optical function. Extensive study of the structures on insect wings have identified Bragg scatterers [1] and anti-reflection surfaces with sub-diffraction limit scale textures [2]. We have previously demonstrated that the nanoscale features on the wings of cicadas can be effectively used as substrates for surface enhanced Raman scattering [2] and have recently shown that these features can be effectively replicated onto the tips of optical fibres [3] with scope for mass production [4].

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Bert Laegel

Kaiserslautern University of Technology

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Sandra Wolff

Kaiserslautern University of Technology

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Nico Irmler

Karlsruhe University of Applied Sciences

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