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Dr. Alexander Welle



Group: ToF-SIMS

We modify and analyze different substrates (from inorganic hard materials like amorphous carbon, to polymers, SurMOFs, SurGels and Self Assembled Monolayers) which can be tailored by tuning their surface chemistries: Click chemistry or SNAP-tags for biomolecule immobilization, compartmentalized substrates for cocultures of cells, laser processed or resist free UV lithographically patterned materials. We are exploring the competitive physisorption or chemisorption of proteins and the effects on the differentiation of cells.

We contribute to the surface analysis platform of the Helmholtz-Programm BioInterfaces and the Karlsruhe Nano Micro Facility. In house Time-of-Flight Secondary Ion Mass Spectrometry (TOF.SIMS5 , ION-TOF, Münster) is applied. ToF-SIMS determines the atomic and molecular composition of the topmost layer of a solid sample. Therefore, the surface is bombarded with high energy Bi clusters or fullerene projectiles (primary ions). Sputtered secondary ions of the sample are separated in a time of flight system and counted. Individual channels of the obtained mass spectra can be presented as images with lateral resolutions of 300-3000nm. If the material of the sample is eroded under the ion bombardment a depth profile is obtained.