Kai Dirscherl
Technical University of Denmark
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Publication
Featured researches published by Kai Dirscherl.
Journal of Micromechanics and Microengineering | 2014
Morten Madsen; Nikolaj A. Feidenhans’l; Poul-Erik Hansen; Jørgen Garnæs; Kai Dirscherl
Polydimethylsiloxane (PDMS) is a widely used material for fabrication of microfluidic devices and for replication of micro- and nanotextured surfaces. Shrinkage of PDMS in the fabrication process can lead to leaking devices and poor alignment of layers. However, corrections to the mold master are seldom applied to counteract the shrinkage of PDMS. Also, to perform metrological measurements using replica techniques one has to take the shrinkage into account. Thus we report a study of the shrinkage of PDMS with several different mixing ratios and curing temperatures. The shrinkage factor, with its associated uncertainty, for PDMS in the range 40 to 120 °C is provided. By applying this correction factor, it is possible to replicate structures with a standard uncertainty of less than 0.2% in lateral dimensions using typical curing temperatures and PDMS mixing ratios in the range 1:6 to 1:20 (agent:base).
ACS Applied Materials & Interfaces | 2014
Svava Davíđsdóttir; Jean-Pierre Petit; Michel Mermoux; Rajashekhara Shabadi; Stela Canulescu; Klaus P. Almtoft; Kai Dirscherl; Rajan Ambat
The photocatalytic behavior of magnetron sputtered anatase TiO2 coatings on copper, nickel, and gold was investigated with the aim of understanding the effect of the metallic substrate and coating-substrate interface structure. Stoichiometry and nanoscale structure of the coating were investigated using X-ray diffraction, Raman spectroscopy, atomic force microscope, and scanning and transmission electron microscopy. Photocatalytic behavior of the coating was explored by using optical spectrophotometry and electrochemical methods via photovoltage, photocurrent, and scanning kelvin probe microscopy measurements. The nature of the metal substrate and coating-substrate interface had profound influence on the photocatalytic behavior. Less photon energy was required for TiO2 excitation on a nickel substrate, whereas TiO2 coating on copper showed a higher band gap attributed to quantum confinement. However, the TiO2 coating on gold exhibited behavior typical of facile transfer of electrons to and from the CB, therefore requiring only a small amount of photon energy to make the TiO2 coating conductive.
Optics Express | 2012
Mirza Karamehmedovic; Poul-Erik Hansen; Kai Dirscherl; Emir Karamehmedović; Thomas Wriedt
An efficient forward scattering model is constructed for penetrable 2D submicron particles on rough substrates. The scattering and the particle-surface interaction are modeled using discrete sources with complex images. The substrate micro-roughness is described by a heuristic surface transfer function. The forward model is applied in the numerical estimation of the profile of a platinum (Pt) submicron wire on rough silicon (Si) substrate, based on experimental Bidirectional Reflectance Distribution Function (BRDF) data.
RSC Advances | 2013
Svava Daviðsdóttir; Kai Dirscherl; Stela Canulescu; Rajashekhara Shabadi; Rajan Ambat
The change in the surface potential of TiO2 coatings upon UV-illumination was investigated on the nanoscale using Scanning Kelvin Probe Force microscopy and on the micro-scale using photo-electrochemical measurements. A good correlation between the two techniques was obtained. The changes in the surface potential of TiO2 coatings upon UV-illumination are closely correlated to the band gap and thickness of the coatings. The inhomogeneity surface potential distribution of a 100 nm TiO2 film indicates a heterogeneous coating. Transition to a homogeneous surface potential distribution was observed with increasing thickness of the TiO2 coating.
Environmental Science and Pollution Research | 2017
Antoni Torras-Rosell; Sabrina Rostgaard Johannsen; Kai Dirscherl; Svava Daviðsdóttir; Christian Sloth Jeppesen; Sascha Louring; Inge Hald Andersen
This study focuses on the characterization of photocatalytic TiO2 coatings using Kelvin probe force microscopy. While most photocatalytic experiments are carried out at a macroscopic scale, Kelvin probe force microscopy is a microscopic technique that is surface sensitive. In order to link microscale results to macroscopic experiments, a simple method to establish the relation between Kelvin probe force microscopy and electrochemical measurements is presented by the calibration of a reference sample consisting of epitaxial deposited Cu-Ni-Au that is used as a transfer standard. The photocatalytic properties of TiO2 at macro- and microscopic scales are investigated by comparing photocatalytic degradation of acetone and electrochemical experiments to Kelvin probe force microscopy. The good agreement between the macro- and microscopic experiments suggests that Kelvin probe force microscopy can be a valuable tool towards the understanding, standardization and design of TiO2-based solutions in photocatalytic applications.
Nanomaterials | 2018
Guanghong Zeng; Kai Dirscherl; Jørgen Garnæs
Atomic force microscopy (AFM) has emerged as a popular tool for the mechanical mapping of soft nanomaterials due to its high spatial and force resolution. Its applications in rigid nanomaterials, however, have been underexplored. In this work, we studied elasticity mapping of common rigid materials by AFM, with a focus on factors that affect the accuracy of elasticity measurements. We demonstrated the advantages in speed and noise level by using high frequency mechanical mapping compared to the classical force volume mapping. We studied loading force dependency, and observed a consistent pattern on all materials, where measured elasticity increased with loading force before stabilizing. Tip radius was found to have a major impact on the accuracy of measured elasticity. The blunt tip with 200 nm radius measured elasticity with deviation from nominal values up to 13% in different materials, in contrast to 122% by the sharp tip with 40 nm radius. Plastic deformation is believed to be the major reason for this difference. Sharp tips, however, still hold advantages in resolution and imaging capability for nanomaterials.
Surface & Coatings Technology | 2013
Svava Daviðsdóttir; Stela Canulescu; Kai Dirscherl; Jørgen Schou; Rajan Ambat
Applied Surface Science | 2014
Visweswara Chakravarthy Gudla; Stela Canulescu; Rajashekhara Shabadi; Kristian Rechendorff; Kai Dirscherl; Rajan Ambat
Surface & Coatings Technology | 2014
Martin Aggerbeck; Stela Canulescu; Kai Dirscherl; Villads Egede Johansen; Sara Lena Josefin Engberg; Jørgen Schou; Rajan Ambat
Applied Surface Science | 2014
Svava Daviðsdóttir; Rajashekhara Shabadi; A.C. Galca; Inge Hald Andersen; Kai Dirscherl; Rajan Ambat