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Experimental optomechanics with silicon micromirrors

Optomechanical coupling between a moving mirror and quantum fluctuations of light first appeared in the context of interferometric gravitational-wave detection [1]. Since then, several schemes involving a cavity with a movable mirror subject to radiation pressure have been proposed either to create non-classical states of light or to perform Quantum Non Demolition measurements of light intensity [2]. Recent progress in low-noise laser sources and low-loss mirrors has made the field experimentally accessible [3].

Understanding the mechanisms of lipid extraction from microalga Chlamydomonas reinhardtii after electrical field solicitations and mechanical stress within a microfluidic device

One way envisioned to overcome part of the issues biodiesel production encounters today is to develop a simple, economically viable and eco-friendly process for the extraction of lipids from microalgae. This study investigates the lipid extraction efficiency from the microalga Chlamydomonas reinhardtii as well as the underlying mechanisms. We propose a new methodology combining a pulsed electric field (PEF) application and mechanical stresses as a pretreatment to improve lipid extraction with solvents. Cells enriched in lipids are therefore submitted to electric field pulses creating pores on the cell membrane and then subjected to a mechanical stress by applying cyclic pressures on the cell wall (using a microfluidic device). Results showed an increase in lipid extraction when cells were pretreated by the combination of both methods. Microscopic observations showed that both pretreatments affect the cell structure. Finally, the dependency of solvent lipid extraction efficiency with the cell wall structure is discussed.

Structural changes of Chlamydomonas reinhardtii cells during lipid enrichment and after solvent exposure

Data are related to Confocal Laser Scanning Microscopy (CLSM) observations of lipid-enriched Chlamydomonas reinhardtii cells under different conditions. Firstly, the impact of stress conditions (nitrogen starvation) on the cell wall structure is assessed. Secondly is described the effect of solvents, in the context of lipid extraction, on the microalgas cell, particularly its lipid droplets, in the perspective of understanding the mechanisms behind solvent extraction of lipids. Furthermore, the role of the cell wall as a barrier to the solvent extraction action is highlighted.

Solid-State Nanopore Easy Chip Integration in a Cheap and Reusable Microfluidic Device for Ion Transport and Polymer Conformation Sensing

Solid-state nanopores have a huge potential in upcoming societal challenging applications in biotechnologies, environment, health, and energy. Nowadays, these sensors are often used within bulky fluidic devices that can cause cross-contaminations and risky nanopore chips manipulations, leading to a short experimental lifetime. We describe the easy, fast, and cheap innovative 3D-printer-helped protocol to manufacture a microfluidic device permitting the reversible integration of a silicon based chip containing a single nanopore. We show the relevance of the shape of the obtained channels thanks to finite elements simulations. We use this device to thoroughly investigate the ionic transport through the solid-state nanopore as a function of applied voltage, salt nature, and concentration. Furthermore, its reliability is proved through the characterization of a polymer-based model of protein-urea interactions on the nanometric scale thanks to a hairy nanopore.

Single Cell Electrical Characterization Techniques

In this chapter the possibility to electrically characterize the electroporation of single cells is discussed. During the electroporation process, the application of pulsed electric field (Transmembrane Voltage Induced by Applied Electric Fields) leads to the partial permeabilization of the cell membrane, opening access to the cytoplasmic compartment for drug delivery, for instance. The electric impedance of the cell is modified by such a treatment. Impedance measurement can thus be employed to characterize the permeabilization effect, on a given angular frequencies range, which leads to an impedance spectrum. The impedance spectrum measurement can be achieved even at the level of single cells. In that case, the distance between the detection microelectrodes and the cell must be considered in order to achieve a satisfactory sensitivity. In addition, when considering the impedance measurement of cells flowing through a microfluidic channel, fast detection is also required, as the cell is present between the measurement electrodes only for a short while. A specific strategy must then be employed to achieve such goal. In this case, instead of screening the whole frequencies spectrum, a few set of frequencies should be selected and mixed to be simultaneously injected prior to synchronous detection. Another way to assess the single cell impedance is the use of indirect methods based on the mechanical behavior of cells that polarize under the application of a stationary or propagative electrical field. In particular, electrorotation experiment provides the electrical characterization of the cell, which is dependent of its level of permeabilization, after the application of electrical field pulses. When such approach is used, the vicinity of electrodes is less critical as the main requirement lays on the homogeneity of the rotating electrical field. Finally, the possibility to focus the electroporation at the subcellular level is discussed in the chapter. Indeed, the use of micro- or nanotechnology permits to localize spatially the electroporation on a tiny portion of the membrane of single cells. Adherent cells can be locally electroporated, using nanosized electrodes, subsequently used to monitor the intracellular potential.