47 research outputs found
Mechanical characterization of individual polycrystalline carbon tubes for use in electrical nano-interconnects
Polycrystalline carbon tubes were generated by CVD inside electrochemically prepared nano-porous anodic aluminium oxide membranes. This method produced nano-tubes without catalyst, featuring polycrystalline and a few layer thick walls. Individual tubes could be isolated and suspended on microfabricated substrates such that they formed single-side clamped beams. These beams were then used to investigate their mechanical properties employing electrostatic forces for bending the tubes beyond their mechanical stability where pull-in occurs, which could be detected by monitoring the current flowing from the tube to the substrate
Functional dependence of resonant harmonics on nanomechanical parameters in dynamic mode atomic force microscopy
Abstract We present a combined theoretical and experimental study of the dependence of resonant higher harmonics of rectangular cantilevers of an atomic force microscope (AFM) as a function of relevant parameters such as the cantilever force constant, tip radius and free oscillation amplitude as well as the stiffness of the sample's surface. The simulations reveal a universal functional dependence of the amplitude of the 6th harmonic (in resonance with the 2nd flexural mode) on these parameters, which can be expressed in terms of a gun-shaped function. This analytical expression can be regarded as a practical tool for extracting qualitative information from AFM measurements and it can be extended to any resonant harmonics. The experiments confirm the predicted dependence in the explored 3-45 N/m force constant range and 2-345 GPa sample's stiffness range. For force constants around 25 N/m, the amplitude of the 6th harmonic exhibits the largest sensitivity for ultrasharp tips (tip radius below 10 nm) and polymers (Young's modulus below 20 GPa). 88
Micro- and nanosystems for biology and medicine
The development of new tools and instruments for biomedical applications based on nano- (NEMS) or microelectromechanical systems technology (MEMS) are bridging the gap between the macro- and the nano-world. The well mastered microtechnique allows controlling many parameters of these instruments, which is essential for conducting reproducible and repeatable experiments in the life sciences. Examples are multifunctional scanning probe sensors for cell biology, an arthroscopic scanning force microscope for minimally invasive medical interventions and a nanopore sensor for single molecule experiments in biochemistry. This paper reviews some of the activities conducted in a fruitful interdisciplinary collaboration between physicists, engineers, biologists and physicians
Scanning probe with tuning fork sensor, microfabricated silicon cantilever and conductive tip for microscopy at cryogenic temperature
A quartz tuning-fork (TF)-based scanning probe is presented for local electrical transport measurements on quantum devices below the liquid 4 He temperature. The TF is utilized to drive and sense the mechanical oscillation of an attached, microfabricated cantilever featuring a conductive tip made of platinum silicide. The microfabricated structure allows the application of an external voltage to the tip, while the cantilever is electrically grounded. The probe was characterized at room temperature, 70 K, and 2 K. It was found that spatial sensitivity decreased with temperature. Imaging a gold surface at 2 K was successfully performed. A number of probes can be batch-fabricated, thus shortening the lead time for conducting experiments in cryogenic scanning force microscopy
Near-field fluorescence imaging with 32 nm resolution based on microfabricated cantilevered probes
Submicron patterns-on-a-chip: Fabrication of a microfluidic device incorporating 3D printed surface ornaments
Manufacturing high throughput in vitro models resembling the tissue microenvironment is highly demanded for studying bone regeneration. Tissues such as bone have complex multiscale architectures insid
Toxicity of lunar dust
The formation, composition and physical properties of lunar dust are
incompletely characterised with regard to human health. While the physical and
chemical determinants of dust toxicity for materials such as asbestos, quartz,
volcanic ashes and urban particulate matter have been the focus of substantial
research efforts, lunar dust properties, and therefore lunar dust toxicity may
differ substantially. In this contribution, past and ongoing work on dust
toxicity is reviewed, and major knowledge gaps that prevent an accurate
assessment of lunar dust toxicity are identified. Finally, a range of studies
using ground-based, low-gravity, and in situ measurements is recommended to
address the identified knowledge gaps. Because none of the curated lunar
samples exist in a pristine state that preserves the surface reactive chemical
aspects thought to be present on the lunar surface, studies using this material
carry with them considerable uncertainty in terms of fidelity. As a
consequence, in situ data on lunar dust properties will be required to provide
ground truth for ground-based studies quantifying the toxicity of dust exposure
and the associated health risks during future manned lunar missions.Comment: 62 pages, 9 figures, 2 tables, accepted for publication in Planetary
and Space Scienc