We experimentally demonstrate an ultra high Q/V nanocavity on SOI substrate. The design is based on modal adaptation within the cavity and allows to measure a quality factor of 58.000 for a modal ...volume of 0.6(lambda/n)(3) . This record Q/V value of 10(5) achieved for a structure standing on a physical substrate, rather than on membrane, is in very good agreement with theoretical predictions also shown. Based on these experimental results, we show that further refinements of the cavity design could lead to Q/V ratios close to 10(6).
Particles manipulation with optical forces is known as optical tweezing. While tweezing in free space with laser beams was established in the 1980s, integrating the optical tweezers on a chip is a ...challenging task. Recent experiments with plasmonic nanoantennas, microring resonators, and photonic crystal nanocavities have demonstrated optical trapping. However, the optical field of a tweezer made of a single microscopic resonator cannot be shaped. So far, this prevents from optically driven micromanipulations. Here we propose an alternative approach where the shape of the optical trap can be tuned by the wavelength in coupled nanobeam cavities. Using these shapeable tweezers, we present micromanipulation of polystyrene microspheres trapped on a silicon chip. These results show that coupled nanobeam cavities are versatile building blocks for optical near-field engineering. They open the way to much complex integrated tweezers using networks of coupled nanobeam cavities for particles or bio-objects manipulation at a larger scale.
This work determines the dielectrophoretic response of surface modified polystyrene and silica colloidal particles by experimentally measuring their Clausius-Mossotti factors. Commercial charged ...particles, fabricated ones coated with fibronectin, and Janus particles that have been grafted with fibronectin on one side only were investigated. We show that the dielectrophoretic response of such particles can be controlled by the modification of the chemistry or the anisotropy of their surface. Moreover, by modelling the polarizabilities of those particles, the dielectric parameters of the particles and the grafted layer of protein can be measured.
The use of surface coating on biomaterials can render the original substratum with new functionalities that can improve the chemical, physical, and mechanical properties as well as enhance cellular ...cues such as attachment, proliferation, and differentiation. In this work, we combined biocompatible polydimethylsiloxane (PDMS) with a biomimetic polyelectrolyte multilayer (PEM) film made of poly(L-lysine) and hyaluronic acid (PLL/HA) for skeletal muscle tissue engineering. By microstructuring PDMS in grooves of a different width (5, 10, 30, and 100 μm) and by modulating the stiffness of the (PLL/HA) films, we guided skeletal muscle cell differentiation into myotubes. We found optimal conditions for both the formation of parallel-oriented myotubes and their maturation. Significantly, the myoblasts were collectively prealigned to the grooves before their differentiation. Before fusion, the highest aspect ratio and orientation of nuclei were observed for the 5 and 10 μm wide micropatterns. The formation of myotubes was observed regardless of the size of the micropatterns, and we found that their typical width was 10-12 μm. Their maturation was characterized by the immunolabeling of type II isomyosin. The amount of myosin striation was not affected by the topography, except for the 5 μm wide micropatterns. We highlighted the spatial constraints that led to an important nuclei deformation and further impairment of maturation within the 5 μm grooves. Altogether, our results show that the PEM film combined with PDMS is a powerful tool that is used for skeletal muscle engineering. This work opens perspectives for the development of skeletal muscle tissue in contact with films containing bioactive peptides or growth factors as well as for the study of pathogenic myotubes.
Janus particles are dissymmetric systems with 2 faces that could present 2 different physical/chemical properties, offering new possibilities in microfluidic research fields. This work presents a ...novel approach of handling the rotation of Janus particles with dielectrophoresis in a determined location at the single level. We first present the manufacturing process of those particles with fluorescent PS beads coated on one side with Au. Then spectroscopic studies investigate their optical responses under fluorescence excitation as a mean to monitor their rotation angle. Finally, Janus particles are injected in an electro-microfluidic chip exerting non-uniform localized electrical fields inside the channel. The microfluidic experiment shows that not only precise 3D localization of those particles can be achieved but moreover that their rotation can be controlled by the gradient of the applied electrical field.
•Micrometric resolution substrates are made at low cost using a videoprojector.•Fabricated patterns could be used as substrates for capillary force assembly.•Arrays of organized particles are made ...using a table-top capillary assembly tool.•This process offers a new bridge between the colloidal domain and the chip world.
In the field of micro- and nanotechnology, most lithography and fabrication tools coming from the microelectronic industry are expensive, time-consuming and may need some masks that have to be subcontracted. Such approach is not suitable for other fields that require rapid prototyping such as chemistry, life science or energy and may hinder research creativity. In this work, we present two table-top equipments dedicated to the fabrication of deterministic colloidal particles assemblies onto micro-structured substrates. We show that, with a limited modification of the optics of a standard videoprojector, it is possible to quickly obtain substrates with thousands of micrometric features. Then, we combine these substrates with thermodynamic colloidal assembly and generate arrays of particles without defects. This work opens the way to a simple and table-top fabrication of devices based on colloidal particles.
Les oléosomes sont des gouttelettes lipidiques limitées par une monocouche de lipides associée à des protéines (oléosines), répandus dans les graines, notamment dans les oléagineux alimentaires comme ...l’arachide. Les oléosines (Arah 10, Ara h 11, Ara h 14, Ara h 15) sont les protéines les plus abondantes des oléosomes. Elles sont constituées d’un cœur hydrophobe de deux hélices-a disposées en épingle à cheveu, qui pénètre dans le contenu lipidique et assure son ancrage dans l’oléosome. Le cœur hydrophobe est prolongé par deux bras structurés en hélices-a, hydrophiles, qui s’étalent à la surface de l’oléosome, au contact du cytoplasme. D’autres protéines (caléosines et steroléosines) de structures plus complexes, moins abondantes, jouent aussi un rôle d’interface avec le cytoplasme. L’IgE-réactivité des oléosines d’arachide a été détectée par western blot et par une approche Basée sur l’utilisation de microbilles fonctionnalisées liées à un extrait purifié d’oléosines, afin d’augmenter la sensibilité du test de détection. Les deux approches ont permis de détecter l’IgEréactivité de tous les sérums (n=15) de patients allergiques à l’arachide testés, avec toutefois des variations d’intensité importantes. En western blot, un nombre très limité de sérums montre une faible IgE-réactivité avec les caléosines. Ces résultats sont discutés.
Measurements are reported on the magnetization reversal in submicron magnetic rings fabricated by high-resolution electron beam lithography and lift-off from cobalt thin films. For all dimensions ...investigated, with diameters of 300-800 nm and a thickness of 10-50 nm, the flux closure state is the stable magnetization configuration. However, with increasing diameter and decreasing film thickness a metastable near single domain state can be obtained during the reversal process in an in-plane applied field.
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