Search Results
Stimulated emission depletion microscopy for imaging of engineered and biological nanostructures
The investigation of interactions between engineered nanostructures and biological systems is a key component in the assessment of potential environmental and health implications due to the increasing application of nanotechnology. Combining the high specificity of bioconjugate fluorescence labeling techniques with the sub-diffraction resolution of Stimulated Emission Depletion (STED) microscopy and state-of-the-art nonlinear image restoration allows the imaging of these interactions on the length scales demanded by the interaction partners. In this article, we give an overview of the experimental approach and discuss its implications on the biological interpretation of the resulting fluorescence micrographs.
The role of the backing layer in the mechanical properties of micrometer-scale fibrillar structures
The contact mechanics of a micro-fabricated fibrillar surface structure made of poly(dimethylsiloxane) (PDMS) was studied in this work. The attachment and detachment of individual fibrils to and from a spherical indenter upon approach and retraction are detected as jumps in force and stiffness. A quantitative model describes the jumps in stiffness values by taking into account the deformation of the backing layer. The results emphasize the importance of long-range interactions in the contact mechanics of elastic materials and confirm the concepts underlying the development of fibrillar adhesive materials.
Size dependent strength of bcc metal micropillars: towards high strength surfaces by micropatterning
The size effect in body-centered cubic (bcc) metals was comprehensively investigated through microcompression tests performed on focused ion beam machined tungsten (W), molybdenum (Mo) and niobium (Nb) pillars, with single slip [235] and multiple slip [001] orientations. The relationship between yield strength and pillar diameter as well as the deformation morphologies were found to correlate with a parameter specific for bcc metals, i.e. the critical temperature Tc. This finding sheds new light on the phenomenon of small-scale plasticity in largely unexplored non-fcc metals. This effect may be used in the patterning of surfaces to achieve higher strengths.
"Gecko-Workshop 2010" - INM initiates new worldwide conference series
In July 2010, scientists from all over the world gathered at INM to discuss gecko inspired adhesion at a workshop entitled "Bioinspired adhesion: from geckos to new products". The talks covered a range of current issues, including natural attachment systems, developments in artificial gecko-mimics, advances in mechanical models and possible products. This was the first dedicated workshop on this topic. The attendees unanimously agreed to create an international workshop series based on the INM example.
Bioinspired pressure actuated adhesive system
We developed a dry snythetic adhesive system inspired by gecko feet that can switch reversibly from adhesion to non-adhesion with applied pressure as external stimulus. Micropatterned polydimethylsiloxane (PDMS) surfaces with pillars of 30 µm length and 10 µm diameter were fabricated using photolithography and moulding. Adhesion properties were determined with a flat probe as a function of preload. For low and moderate applied compressive preloads, measured adhesion was 7.5 times higher on the patterned surfaces than on flat controls whereas for high preloads adhesion dropped to very low values. In situ imaging showed that the increased preload caused the pillars to deform by bending and/or buckling and to lose their adhesive contact. The elasticity of PDMS aids the pillar recovery to the upright position upon removal of preload enabling repeatability of the switch. Such systems have promising properties e.g. for industrial pick-and-carry operations.
Biological materials - bioinspiration on different length scales
This article investigates nacre and peacock feather rachis from a molecular and structural point of view, in addition to unifying principles in nature that may control hierarchical functions. This biological material serves as an example for deciphering basic principles in nature that may subsequently be used to design new artificial materials and structures.
A new approach for a slurry based coating system for the prevention of high-temperature oxidation
[no abstract available]
The intracellular localization of inorganic engineered versus biogenic materials: a comparison
The uptake of engineered nanoobjects into cells is assumed to significantly account for their potential toxicity. By internalisation, nanoparticles are at least temporarily trapped in the confined volume of a single cell and come into close contact with cellular components, like organelles, structural proteins, enzymes or signalling molecules. As cells are highly structured entities, exhibiting various types of chemically and biologically distinct compartments, first of all the uptake mechanism determines which types of molecules are encountered. In this review, an introduction into the compartmentalisation of cells as well as some uptake processes is given. The localisation of engineered materials within cells of human and animal origin is exemplified. On the other hand, many living organisms are known for their ability to intracellularly precipitate inorganic structures. Some of these biogenic materials are chemically and structurally similar to artificially generated nanostructures. Therefore, the localisation of some biogenic structures within cells is also illustrated. Finally, the relevance of the specific cellular localisation for toxicity is discussed.