Ion beam etching redeposition for 3D multimaterial nanostructure manufacturing

A novel fabrication method based on the local sputtering of photoresist sidewalls during ion beam etching is presented. This method allows for the manufacture of three-dimensional multimaterial nanostructures at the wafer scale in only four process steps. Features of various shapes and profiles can be fabricated at sub-100-nm dimensions with unprecedented freedom in material choice. Complex nanostructures such as nanochannels, multimaterial nanowalls, and suspended networks were successfully fabricated using only standard microprocessing tools. This provides an alternative to traditional nanofabrication techniques, as well as new opportunities for biosensing, nanofluidics, nanophotonics, and nanoelectronics

Statistical Aging and Non Ergodicity in the Fluorescence of Single Nanocrystals

The relation between single particle and ensemble measurements is adressed for semiconductor CdSe nanocrystals. We record their fluorescence at the single molecule level and analyse their emission intermittency, which is governed by unusual random processes known as Levy statistics. We report the observation of statistical aging and ergodicity breaking, both related to the occurrence of Levy statistics. Our results show that the behaviour of ensemble quantities, such as the total fluorescence of an ensemble of nanocrystals, can differ from the time averaged individual quantities, and must be interpreted with care.Comment: 4 pages, 3 figure

Intracellular Recording of Cardiomyocyte Action Potentials with Nanopatterned Volcano-Shaped Microelectrode Arrays

Micronanotechnology-based multielectrode ar- rays have led to remarkable progress in the field of transmembrane voltage recording of excitable cells. However, providing long-term optoporation- or electroporation-free intracellular access remains a considerable challenge. In this study, a novel type of nanopatterned volcano-shaped micro- electrode (nanovolcano) is described that spontaneously fuses with the cell membrane and permits stable intracellular access. The complex nanostructure was manufactured following a simple and scalable fabrication process based on ion beam etching redeposition. The resulting ring-shaped structure provided passive intracellular access to neonatal rat cardiomyocytes. Intracellular action potentials were successfully recorded in vitro from different devices, and continuous recording for more than 1 h was achieved. By reporting transmembrane action potentials at potentially high spatial resolution without the need to apply physical triggers, the nanovolcanoes show distinct advantages over multielectrode arrays for the assessment of electrophysiological characteristics of cardiomyocyte networks at the transmembrane voltage level over time

Volcano-Shaped Scanning Probe Microscopy Probe for Combined Force-Electrogram Recordings from Excitable Cells

Atomic force microscopy based approaches have led to remarkable advances in the field of mechanobiology. However, linking the mechanical cues to biological responses requires complementary techniques capable of recording these physiological characteristics. In this study, we present an instrument for combined optical, force, and electrical measurements based on a novel type of scanning probe microscopy cantilever composed of a protruding volcano-shaped nanopattemed microelectrode (nanovolcano probe) at the tip of a suspended microcantilever. This probe enables simultaneous force and electrical recordings from single cells. Successful impedance measurements on mechanically stimulated neonatal rat cardiomyocytes in situ were achieved using these nanovolcano probes. Furthermore, proof of concept experiments demonstrated that extracellular field potentials (electrogram) together with contraction displacement curves could simultaneously be recorded. These features render the nanovolcano probe especially suited for mechanobiological studies aiming at linking mechanical stimuli to electrophysiological responses of single cells