Automatic eye reconstruction for radiotherapy

International audienceno abstrac

Response of HEK cells to dielectrophoresis for increasing medium conductivities.

<p>nDEP and pDEP are applied at <i>f</i>  =  1 kHz and <i>f</i>  =  200 kHz, respectively. The arrow represents cell motion during 5 frames (300 ms), the picture being the last image. DEP is stronger at low conductivities compared to EHD forces so cells experience larger displacement at higher velocities at low conductivities.</p

Rotation study of three human cell lines.

<p><b>(a1)</b> Time-lapse sequence images of the rotation of HEK cells in the z-axis, in presence of 1 µm polystyrene colloid (highlighted in blue circles). Particles were added to observe medium stream lines. The red circle pinpoints a visible organelle. Rotation is studied at σ_m  =  2.10⁻² S/m when varying <b>(a2)</b> magnitude of the electric field at <i>f</i>  =  45 kHz or <b>(a3)</b> frequency at magnitude 0.065 V/µm (V = 10 Vp-p). The dashed line plots the values of |Re[CMF(ω)]| at the same frequencies, bringing out the relation between DEP effect and ETE. Rotation studies of <b>(b)</b> of JURKAT cells and <b>(c)</b> PC3 cells (electric field magnitude is 0.089 V/µm (V = 4Vp-p) and σ_m  =  2 10⁻² S/m.). The inset on the lower part of the graphs shows the number of cells used for each mean value.</p

Table of the dielectric parameters for three human cell lines.

<p>The cytoplasm conductivity σ₃ and membrane capacitance <i>C_mem</i> are calculated from experimental fit to the competitive model.</p

Summary of cells behaviors at (a) σ_m = 2.10⁻⁴ S/m and (b) σ_m = 2.10⁻² S/m.

<p>Photographs and schemes illustrate the cell motion for typical frequencies and magnitudes with corresponding graphs of the DEP (U_DEP, green line) and EHD (U_EHD, in red) velocities. The velocities were calculated according to the theoretical model presented in the first paragraph and position of the field was taken for x = 1 µm. The boxed text refers to the related paragraph.</p

Single shell model of a mamalian cell with dielectric parameters annoted.

<p>Single shell model of a mamalian cell with dielectric parameters annoted.</p

A near-field actuated optical nanocavity

International audienceWe demonstrate here that switching and tuning of a nanocavity resonance can be achieved by approaching a sub-micrometer tip inside its evanescent near-field. The resonance energy is tuned over a wide spectral range (/~10-3) without significant deterioration of the cavity peaktransmittance and of the resonance linewidth. Such a result is achieved by taking benefits from a weak tip-cavity interaction regime in which the tip behaves as a pure optical path length modulato

Nano-manipulation of confined electromagnetic fields with a near-field probe

International audienc

On-chip photonic tweezers for photonics, microfluidics, and biology

International audienceNear-field optical forces arise from evanescent electromagnetic fields and can be advantageously used for on-chip optical trapping. In this work, we investigate how evanescent fields at the surface of photonic cavities can efficiently trap micro-objects such as polystyrene particles and bacteria. We study first the influence of trapped particle’s size on the trapping potential and introduce an original optofluidic near-field optical microscopy technique. Then we analyze the rotational motion of trapped clusters of microparticles and investigate their possible use as microfluidic micro-tools such as integrated micro-flow vane. Eventually, we demonstrate efficient on-chip optical trapping of various kinds of bacteria