A crucial part of the drug discovery process involves imaging the response of thousands of cell cultures to candidate drugs. Quantitative parameters from these “high content screens”, such as protein expression and cell morphology, are extracted from fluorescence and brightfield micrographs. Due to the sheer number of cells that need to imaged for adequate statistics, the imaging time itself is a major bottleneck. Automated microscopes image small fields-of-view (FOVs) serially, which are then stitched together to form gigapixel-scale mosaics. We have developed a microscopy architecture that reduces mechanical overhead of traditional large field-of-view by parallelizing the image capture process. Instead of a single objective lens imaging FOVs one by one, we employ a microlens array for continuous photon capture, resulting in a 3-fold throughput increase. In this contribution, we present the design and imaging results of this microscopy architecture in three different contrast modes: multichannel fluorescence, hyperspectral fluorescence and brightfield.
We present an optofluidic measurement system that quantifies cell volume, dry mass, and nuclear morphology of neutrophils in high-throughput. While current clinical hematology analyzers can differentiate neutrophils from a blood sample, they do not give other quantitative information beyond their count. In order to better understand the distribution of neutrophil phenotypes in a blood sample, we perform two distinct multivariate measurements. In both measurements, white blood cells are driven through a microfluidic channel and imaged while in flow onto a color camera using a single exposure. In the first measurement, we quantify cell volume, scattering strength, and cell dry mass by combining quantitative phase imaging with dye exclusion cell volumetric imaging. In the second measurement, we quantify cell volume and nuclear morphology using a nucleic acid fluorescent stain. In this way, we can correlate cell volume to other cellular characteristics, which would not be possible using an electrical coulter counter. Unlike phase imaging or cell scattering analysis, the optical coulter counter is capable of quantifying cell volume virtually independent of the cell’s refractive index and unlike optical tomography, measurements are possible on quickly flowing cells, enabling high-throughput.
We present an opto-fluidic measurement system that quantifies cell volume, dry mass and nuclear morphology of neutrophils in high-throughput. While current clinical hematology analyzers can differentiate neutrophils from a blood sample, they do not give other quantitative information beyond their count. In order to better understand the distribution of neutrophil phenotypes in a blood sample, we perform two distinct multivariate measurements. In both measurements, white blood cells are driven through a microfluidic channel and imaged while in flow onto a color camera using a single exposure. In the first measurement, we quantify cell volume, scattering strength, and cell dry mass by combining quantitative phase imaging with dye exclusion cell volumetric imaging. In the second measurement, we quantify cell volume and nuclear morphology using a nucleic acid fluorescent stain. In this way, we can correlate cell volume to other cellular characteristics, which would not be possible using an electrical coulter counter. Unlike phase imaging or cell scattering analysis, the optical coulter counter is capable of quantifying cell volume virtually independent of the cell’s refractive index and unlike optical tomography, measurements are possible on quickly flowing cells, enabling high-throughput.
Using a Fresnel zone plate, we demonstrate optical trapping with a larger numerical aperture than is commonly available with commercial objective lenses. The zone plate is fabricated onto the inner wall of the fluidic cell and, consequently, focusing is free from on axis aberrations due to an absence of dielectric interfaces. Using zone plates with extremely large focusing angles, we observe an enhanced ellipticity in the trapping volume. For a zone plate with a numerical aperture of 0.986nwater (1.308), we observe a trapping stiffness that is more than four times stiffer perpendicular to the polarization than parallel to the polarization. By rotating the incident linear polarization state, the trapping stiffness along a given direction can be modulated by a factor of four. The ellipticity in the focal volume is due to the presence of an axial field component whose magnitude is proportional to the sine of the focusing angle of the lens.
We present a method for manipulating individual sites in a 2-D optical lattice that enables the creation of defects within otherwise periodic light patterns. The modified optical lattice is created by interference of plane waves and spiral phase waves. Spiral phase modulation creates an optical vortex that is well suited for addressing single rows of the optical lattice owing to the localized wrap of the phase front. Local fringes can be split, annihilated, or have their size tuned by controlling the charge and location of the vortex cores. These properties provide a connection between dislocations in crystals, waves, and optical lattices.
We show experimental results of anomalous refraction through a photonic crystal membrane. The membrane layer consists of a thin polymer film suspending a triangular array of silicon pillars. Light is coupled into the photonic crystal (PC) through ridge waveguides etched onto a silicon substrate. By altering the shape of the tip of the input waveguides, we can shape the light that is incident into the PC. In this paper we show that when we shape the field to be quasi point source like, the PC focuses the incident light onto a deflection block placed behind the membrane structure. We experimentally observe focusing of both TE and TM light inside the PC. In the same structure we have previously shown that when we illuminate the PC with a much broader beam incident at an angle, the light negatively refracts through the crystal. We designed the device so that it is capable of being stretched by mechanical actuators, which will stretch the polymer film and silicon lattice and distort the photonic band structure. Mechanical stretching of the dimensions of the flexible PC makes possible a device that can dynamically change its beam steering and focusing properties.
We report data on a new nanophotonic device based on a 2-D slab silicon photonic crystal (PC) matrix composed of a periodic array of high index silicon pillars embedded within a flexible low index polyimide matrix. To our knowledge, for the first time, negative refraction based on the superprism effect is reported in a 2-D silicon-based photonic crystal device. This work has a huge potential in various applications employed within silicon-based photonic crystal systems such as super-lenses, tunable filters, and optical switches.
The device, designed for 1.54 μm infrared light, is composed of a triangular array of silicon pillars of diameter 400 nm with a lattice spacing of 616 nm embedded in a thin 400 nm thick polyimide matrix. Small changes in the incoming angle of light can produce large changes in the direction of the outgoing light near zero stress.
Silicon pillars are formed by RIE etching and polyimide is then spun on, baked and etched to form the PC device. The PC matrix is then released from the oxide with a BOE etch. Samples with incident angles in the range of 0° ~ 8° have been tested. Strong negative refraction on the order of 50° is seen in the PC with the incident angle of 8°. This is in close agreement with the simulated results and clearly demonstrates the effectiveness of the photonic crystal device.
We report a tunable nanophotonic device concept based on flexible photonic crystal, which is comprised of a periodic array of high index dielectric material and a low index flexible polymer. Tunability is achieved by applying mechanical force with nano-/micro-electron-mechanical system actuators. The mechanical stress induces changes in the periodicity of the photonic crystal and consequently modifies the photonic band structure. To demonstrate the concept, we theoretically investigated the effect of mechanical stress on the anomalous refraction behavior and observed a very wide tunability in the beam propagation direction. Extensive experimental studies on fabrication and characterizations of the flexible photonic crystal structures were also carried out. High quality nanostructures were fabricated by e-beam lithography. Efficient coupling of laser beam and negative refraction in the flexible PC structures have been demonstrated. The new concept of tunable nanophotonic device provides a means to achieve real-time, dynamic control of photonic band structure and will thus expand the utility of photonic crystal structures in advanced nanophotonic systems.
We present a method for manipulating
individual sites in an optical lattice which enables the creation
of defects within otherwise periodic light patterns. The modified
optical lattice is created by interference of plane waves and
spiral phase waves. Spiral phase modulation and the optical
vortices that result are well suited for addressing single rows of
fringes in the lattice owing to the localized wrap of the phase
front. The size and shape of local fringes can be tuned or
dynamically split and recombined by controlling the relative phase
of the incident waves.
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