Light sheet fluorescence microscopy using axi-symmetric binary phase filters.

Light sheet fluorescence microscopy (LSFM) has become an indispensable tool in biomedical studies owing to its depth-sectioning capability and low photo-bleaching. The axial resolution in LSFM is determined mainly by the thickness of the illumination sheet, and a high numerical-aperture lens is thus preferred in the illumination to increase the axial resolution. However, a rapid divergence of the illumination beam limits the effective field-of-view (FoV), that provides high-resolution images.

Three-Step Thermal Drawing for Rapid Prototyping of Highly Customizable Microneedles for Vascular Tissue Insertion.

Microneedles (MNs) have been extensively developed over the last two decades, and highly efficient drug delivery was demonstrated with their minimal invasiveness via a transdermal route. Recently, MNs have not only been applied to the skin but also to other tissues such as blood vessels, scleral tissue, and corneal tissue. In addition, the objective of the MN application has been diversified, ranging from drug delivery to wound closure and biosensing.

Depthwise-controlled scleral insertion of microneedles for drug delivery to the back of the eye.

To treat retinal diseases, intravitreal injection is commonly performed to deliver therapeutic agents to the eye. However, intravitreal injection poses potential risks of ocular complications such as endophthalmitis, retinal detachment, and ocular hemorrhage. Thus, it is desired to develop a minimally invasive and therapeutically effective ocular drug delivery system without full penetration into the sclera.

Design of binary phase filters for depth-of-focus extension via binarization of axisymmetric aberrations.

We present a novel design approach for a binary phase mask with depth-of-focus (DoF) extension ability. Our method considers that the binarized version of an axisymmetric continuous phase pupil generates twin-intensity profiles that are symmetric with respect to the focal plane, each of which resembles the focal behavior of its continuous original. The DoF extension is realized by repositioning and coherently summing the twin foci to achieve an elongated focus along the axial direction.

Color-coded LED microscopy for quantitative phase imaging: Implementation and application to sperm motility analysis.

Color-coded light-emitting diode (LED) microscopy (cLEDscope) is a novel computational microscopy technique capable of multi-contrast and quantitative phase imaging of biological specimens using color-multiplexed illumination. Using specially designed LED patterns, it is capable of recording multiple differential phase contrast (DPC) images in a single exposure and employs a computational algorithm to retrieve the phase distribution of the specimens. Herein, we describe the detailed procedures in the cLEDscope implementation for quantitative phase imaging.

Smartphone-based multi-contrast microscope using color-multiplexed illumination.

We present a portable multi-contrast microscope capable of producing bright-field, dark-field, and differential phase contrast images of thin biological specimens on a smartphone platform. The microscopy method is based on an imaging scheme termed "color-coded light-emitting-diode (LED) microscopy (cLEDscope)," in which a specimen is illuminated with a color-coded LED array and light transmitted through the specimen is recorded by a color image sensor. Decomposition of the image into red, green, and blue colors and subsequent computation enable multi-contrast imaging in a single shot.

Single-exposure quantitative phase imaging in color-coded LED microscopy.

We demonstrate single-shot quantitative phase imaging (QPI) in a platform of color-coded LED microscopy (cLEDscope). The light source in a conventional microscope is replaced by a circular LED pattern that is trisected into subregions with equal area, assigned to red, green, and blue colors. Image acquisition with a color image sensor and subsequent computation based on weak object transfer functions allow for the QPI of a transparent specimen.

A Rapid and Chemical-free Hemoglobin Assay with Photothermal Angular Light Scattering.

Photo-thermal angular light scattering (PT-AS) is a novel optical method for measuring the hemoglobin concentration ([Hb]) of blood samples. On the basis of the intrinsic photothermal response of hemoglobin molecules, the sensor enables high-sensitivity, chemical-free measurement of [Hb]. [Hb] detection capability with a limit of 0.

Color-coded LED microscopy for multi-contrast and quantitative phase-gradient imaging.

We present a multi-contrast microscope based on color-coded illumination and computation. A programmable three-color light-emitting diode (LED) array illuminates a specimen, in which each color corresponds to a different illumination angle. A single color image sensor records light transmitted through the specimen, and images at each color channel are then separated and utilized to obtain bright-field, dark-field, and differential phase contrast (DPC) images simultaneously.

Frequency- and spectrally-encoded confocal microscopy.

We describe a three-dimensional microscopy technique based on spectral and frequency encoding. The method employs a wavelength-swept laser to illuminate a specimen with a spectrally-dispersed line focus that sweeps over the specimen in time. The spatial information along each spectral line is further mapped into different modulation frequencies.

Spectrally encoded slit confocal microscopy using a wavelength-swept laser.

We present an implementation of spectrally encoded slit confocal microscopy. The method employs a rapid wavelength-swept laser as the light source and illuminates a specimen with a line focus that scans through the specimen as the wavelength sweeps. The reflected light from the specimen is imaged with a stationary line scan camera, in which the finite pixel height serves as a slit aperture.

Label-free cell-based assay with spectral-domain optical coherence phase microscopy.

Quantitative measurement of dynamic responses of unstained living cells is of great importance in many applications ranging from investigation of fundamental cellular functions to drug discoveries. Conventional optical methods for label-free cell-based assay examine cellular structural changes proximal to sensor surfaces under external stimuli, but require dedicated nanostructure-patterned substrates for operation. Here, we present a quantitative imaging method, spectral-domain optical coherence phase microscopy (SD-OCPM), as a viable optical platform for label-free cell-based assay.

Photothermal spectral-domain optical coherence reflectometry for direct measurement of hemoglobin concentration of erythrocytes.

A novel optical detection method for hemoglobin concentration is described. The hemoglobin molecules consisting mainly of iron generate heat upon their absorption of light energy at 532 nm, which subsequently changes the refractive index of the blood. We exploit this photothermal effect to determine the hemoglobin concentration of erythrocytes without any preprocessing of blood.