Showing papers by "Georg Schitter published in 2005"

Data acquisition system for high speed atomic force microscopy

Abstract: With the development of atomic force microscopes that allow higher scan speeds, the need for data acquisition systems (DAQ) that are capable of handling the increased amounts of data in real time arises We have developed a low cost data acquisition and scan control system around a commercially available DAQ board in a WINDOWS environment By minimizing the involvement of the processor in the data transfer using direct memory access, and generation of the scan signals synchronously with the data acquisition, we were able to record 30 frames per second with a pixel resolution of 150×150pixels and 14bit per channel

Sacrificial bonds in the interfibrillar matrix of bone.

Abstract: A remarkable self-healing, toughening and strengthen-ing system, the sacrificial bonds and hidden length system,is widespread in nature: especially in "glues" in remarkablytough nanocomposite biomaterials such as bone, abaloneshell and diatoms. Abalone shell is 97% crystalline calciumcarbonate plates by weight, but is 3,000 times more fractureresistant than pure calcium carbonate

On Recent Developments for High-Speed Atomic Force Microscopy

Abstract: � Abstract— The atomic force microscope (AFM) is limited in imaging speed by the bandwidth and dynamic behavior of the actuators and mechanical parts. For high-speed imaging all AFM components have to be optimized in performance. Here, we present improvements of the force sensor, the scanner, the controller, and the data acquisition system. By combining all these improvements, the next generation AFMs will enable imaging speeds more than two orders of magnitude faster than current commercial AFM systems.

High-speed photography of human trabecular bone during compression

Abstract: The mechanical properties of healthy and diseased bone tissue are extensively studied in mechanical tests. Most of this research is motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates simulating conditions experienced in individuals during falls. Apparent strains were found to translate to a broad range of local strains. Moreover, strained trabeculae were seen to whiten with increasing strain. We hypothesize that the effect seen is due to microcrack formation in these areas, similar to stress whitening seen in synthetic polymers. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also of high deformation. We believe that this method will allow further insights into bone failure mechanisms, and help toward a better understanding of the processes involved in bone failure.

Novel techniques for high-resolution functional imaging of trabecular bone

Abstract: In current biological and biomedical research, quantitative endpoints have become an important factor of success. Classically, such endpoints were investigated with 2D imaging, which is usually destructive and the 3D character of tissue gets lost. 3D imaging has gained in importance as a tool for both, qualitative and quantitative assessment of biological systems. In this context synchrotron radiation based tomography has become a very effective tool for opaque 3D tissue systems. Results from a new device are presented enabling the 3D investigation of trabecular bone under mechanical load in a time-lapsed fashion. Using the highly brilliant X-rays from a synchrotron radiation source, bone microcracks and an indication for un-cracked ligament bridging are uncovered. 3D microcrack analysis proves that the classification of microcracks from 2D images is ambiguous. Fatigued bone was found to fail in burst-like fashion, whereas non-fatigued bone exhibited a distinct failure band. Additionally, a higher increase in microcrack volume was detected in fatigued in comparison to non-fatigued bone. Below the spatial resolution accessible with synchrotron radiation tomography we investigated native and fractured bone surfaces on the molecular scale with atomic force microscopy. The mineralized fibrils detected on fracture surfaces give rise to the assumption that the mineral-mineral interface is the weakest link in bone. The presented results show the power of functional micro-imaging, as well as the possibilities for AFM imaging (functional nano-imaging) in this context.

A new technique for imaging mineralized fibrils on bovine trabecular bone fracture surfaces by atomic force microscopy

Abstract: High resolution atomic force microscopy (AFM) images of bovine trabecular bone fracture surfaces reveal individual fibrils coated with extrafibrillar mineral particles. The mineral particles are distinctly different in different regions. In some regions the particles have average dimensions of (70 ± 35) nm along the fibrils and about half that across the fibrils. In other regions they are smaller and rounder, of order (53 ± 14) nm both along and across the fibrils. In other regions they are smaller and rounder, of order (25 ± 15) nm both along and across the fibrils, with more rounded top surfaces. Significantly, we rarely observed bare collagen fibrils. If the observed particles can be verified to be native extrafibrillar mineral, this could imply that the fractures which created the observed areas propagated within the mineralized extrafibrillar matrix.