Hermetic seal | EPFL Graph Search

A hermetic seal is any type of sealing that makes a given object airtight (preventing the passage of air, oxygen, or other gases). The term originally applied to airtight glass containers, but as technology advanced it applied to a larger category of materials, including rubber and plastics. Hermetic seals are essential to the correct and safe functionality of many electronic and healthcare products. Used technically, it is stated in conjunction with a specific test method and conditions of use. Etymology The word hermetic comes from the Greek god Hermes. A hermetic seal comes from alchemy in the tradition of Hermeticism. The legendary Hermes Trismegistus supposedly invented the process of making a glass tube airtight using a secret seal. Uses Some kinds of packaging must maintain a seal against the flow of gases, for example, packaging for some foods, pharmaceuticals, chemicals and consumer goods. The term can describe the result of some food preservation p

Nanovolcano microelectrode arrays: toward long-term on-demand registration of transmembrane action potentials by controlled electroporation

Arnaud Bertsch, Etienne de Coulon, Benoît Xavier Emmanuel Desbiolles, Nicolas Grégoire Maïno, Philippe Renaud, Stephan Rohr

Volcano-shaped microelectrodes (nanovolcanoes) functionalized with nanopatterned self-assembled monolayers have recently been demonstrated to report cardiomyocyte action potentials after gaining spontaneous intracellular access. These nanovolcanoes exhibit recording characteristics similar to those of state-of-the-art micro-nanoelectrode arrays that use electroporation as an insertion mechanism. In this study, we investigated whether the use of electroporation improves the performance of nanovolcano arrays in terms of action potential amplitudes, recording durations, and yield. Experiments with neonatal rat cardiomyocyte monolayers grown on nanovolcano arrays demonstrated that electroporation pulses with characteristics derived from analytical models increased the efficiency of nanovolcano recordings, as they enabled multiple on-demand registration of intracellular action potentials with amplitudes as high as 62 mV and parallel recordings in up to ~76% of the available channels. The performance of nanovolcanoes showed no dependence on the presence of functionalized nanopatterns, indicating that the tip geometry itself is instrumental for establishing a tight seal at the cell–electrode interface, which ultimately determines the quality of recordings. Importantly, the use of electroporation permitted the recording of attenuated cardiomyocyte action potentials during consecutive days at identical sites, indicating that nanovolcano recordings are nondestructive and permit long-term on-demand recordings from excitable cardiac tissues. Apart from demonstrating that less complex manufacturing processes can be used for next-generation nanovolcano arrays, the finding that the devices are suitable for performing on-demand recordings of electrical activity from multiple sites of excitable cardiac tissues over extended periods of time opens the possibility of using the devices not only in basic research but also in the context of comprehensive drug testing.

2020

Guided-wave micro-electro-mechanical systems (MEMS) optical switches for telecommunication applications

Roland Guerre

The present thesis deals with Micro-Electro-Mechanical Systems (MEMS) optical switches for telecommunication applications. The aim is to study new type of microsystems for guided-wave optical switching applications. Two projects have been investigated. The first part addresses a novel technological and design study of N×N optical switch integration with planar waveguides and vertical displacement micro-mirrors. Novel suspended MEMS mechanical platform on SOI wafer were designed and realized and technological processes for optimization of micro-mirrors quality have been developed. The motivation of this study was related to initial collaboration with the company Memscap S.A. which was looking for compact and fast N×N optical switches based on planar waveguides. One of the key issue being waveguide integration, a concept of a hermetic packaging with two wafers assembly where a waveguide wafer is placed face down on top of MEMS electrostatic devices with vertical micro-mirrors has been developed. Vertical micro-mirrors have been fabricated in SU8 photopolymer or in single crystalline silicon. For integration of silicon mirrors, a new simple two-steps DRIE pattern transfer that allow simultaneous fabrication of good quality silicon mirrors and of recessed mechanical platform has been demonstrated. The platform has been analysed through its resonance behaviour. The strong effect of mechanical non-linearity which was observed in clamped suspension can be exploited to increase the control range of the electrostatic actuator. During the first part of this work on MEMS optical switches based on planar waveguides, a totally new approach that use hollow waveguide instead of solid core waveguide has been developed. The primary motivation was whether it was possible to integrate a micromechanical switch composed of a vertical silicon cantilever beam mechanism inside the air core of the hollow waveguide. Silicon Planar Hollow Waveguides (PHW) have been designed, realized and tested with different optical coatings: a metallic gold coating, dielectric bilayers based on the principle of AntiResonant Reflective Optical Waveguide (ARROW) and bare silicon. The influence of ARROW layers on hollow planar waveguides has been investigated. The very first PHW with integrated 1×2 optical switching have been manufactured and characterized. Switching times better than 10 μs were measured with the produced devices. The switching speed was about 100 times higher to other MEMS optical switches based on micro-mirrors.

EPFL2005

Intracellular recording of cardiomyocyte action potentials with nanopatterned volcano-shaped microelectrodes

Benoît Xavier Emmanuel Desbiolles

Micro-nanotechnology based multielectrode arrays have led to remarkable progress in the field of transmembrane voltage recordings of excitable cells. However, electrode geometries alone have failed to produce a cell-electrode interface that is sufficiently robust and stable over extended periods of time to perform high-quality electrophysiological recordings. This thesis addresses the current limitations of micro-nanoelectrode arrays with a particular focus on whether patterning protruding microelectrodes with nanometer-wide biomimetic self-assembled monolayers that fuse with the cell membrane, significantly improves the quality of the electrophysiological recordings when compared to state-of-the-art technology. The first step involved developing a novel nanofabrication process exploiting the sputtering of photoresist sidewalls during Ar+ ion beam etching to rapidly manufacture sub-100-nm complex multimaterial nanostructures at the wafer scale. Ion beam etching redeposition was subsequently used to manufacture a novel nanopatterned volcano-shaped microelectrode (nanovolcano) array integrating most of the recent technological advances from the literature into an original structure. Electrophysiological studies on neonatal rat cardiomyocyte monolayers demonstrated that nanovolcanoes enabled in vitro electroporation-free intracellular recordings of cardiomyocyte action potentials. The recordings lasted more than one continuous hour with amplitudes as high as 20 mV from nearly 30 % of the device's channels. The second phase investigated whether the use of electroporation improved the performance of nanovolcano arrays in terms of action potential amplitudes, recording durations, and yields. Experiments with neonatal rat cardiomyocyte monolayers grown on nanovolcano arrays showed that electroporation increased the efficiency of nanovolcano recordings as it enabled on-demand multiple registration of intracellular action potentials with amplitudes as high as 62 mV and parallel recordings in up to approximately 76 % of the available channels over consecutive days. The performance of nanovolcanoes showed no dependence on the presence of functional nanopatterns, indicating that the tip geometry itself was instrumental for establishing the tight seal at the cell-electrode interface. These results suggest that nanovolcanoes could prove useful not only for basic research but also for comprehensive drug testing in cardiac research. Preliminary studies performed with hippocampal neonatal rat neurons demonstrated that nanovolcano arrays permit the recording of non-attenuated neuronal action potentials in addition to, potentially, subthreshold activity featuring a high signal-to-noise ratio. These results expand the function of nanovolcano arrays to other kinds of electrogenic cells and open new avenues for the field of neuroscience. During an exploratory phase, a nanovolcano electrode was integrated at the tip of a suspended cantilever (nanovolcano probe) to conduct combined-force electrophysiological recordings. Proof-of-concept experiments on neonatal rat cardiomyocytes demonstrated that extracellular field potentials and contraction displacement curves could be recorded simultaneously. These features render the nanovolcano probe especially suited for mechanobiological studies aiming at linking mechanical stimuli to the electrophysiological responses of single cells.

EPFL2020