The gold standard of microfluidic fabrication techniques, SU-8 patterning, requires photolithography equipment and facilities and is not suitable for 3D microfluidics. A 3D printer is more convenient and may achieve high resolutions comparable to conventional photolithography, but only with select materials. Alternatively, 5-axis computer numerical control (CNC) micro-milling machines can efficiently prototype structures with high resolutions, high aspect ratios, and non-planar geometries from a variety of materials.
View Article and Find Full Text PDFOvulation is critical for sexual reproduction and consists of the process of liberating fertilizable oocytes from their somatic follicle capsules, also known as follicle rupture. The mechanical force for oocyte expulsion is largely unknown in many species. Our previous work demonstrated that ovulation, as in mammals, requires the proteolytic degradation of the posterior follicle wall and follicle rupture to release the mature oocyte from a layer of somatic follicle cells.
View Article and Find Full Text PDFMost common cytometry methods, including flow cytometry, observe suspended or fixed cells and cannot evaluate their structural roles in 3D tissues. However, cellular physical interactions are critical in physiological, developmental, and pathological processes. Here, we present a novel optical visco-elastography that characterizes single-cellular physical interactions by applying in-situ micro-mechanical perturbation to live microtissues under 3D lightsheet microscopy.
View Article and Find Full Text PDFThe proper formation of the vertebrate embryonic heart relies on various mechanical forces which determine its form and function. Measuring these forces at the microscale of the embryo is a challenge. We propose a new tool utilizing high-resolution optical elastography and stiffness measurements of surrounding tissues to non-invasively track the changes in the pressure exerted by the heart on the neighboring yolk, as well as changes in contractile patterns during early cardiac growth in-vivo, using the zebrafish embryo as a model system.
View Article and Find Full Text PDFMulticellular cancer spheroids are an in vitro tissue model that mimics the three-dimensional microenvironment. As spheroids grow, they develop the gradients of oxygen, nutrients, and catabolites, affecting crucial tumor characteristics such as proliferation and treatment responses. The measurement of spheroid stiffness provides a quantitative measure to evaluate such structural changes over time.
View Article and Find Full Text PDFWe evaluated the elasticity of live tissues of zebrafish embryos using label-free optical elastography. We employed a pair of custom-built elastic microcantilevers to gently compress a zebrafish embryo and used optical-tracking analysis to obtain the induced internal strain. We then built a finite element method (FEM) model and matched the strain with the optical analysis.
View Article and Find Full Text PDFBy combining novel micro-scale manipulation cantilevers with commercially available, widely used 3D light microscopy, we were able to develop a new method of 3D elastography specialized for the analysis of 3D microtumors. Existing mechanical characterization methods are available for the study of single cells, using forces in the range of sub pN to a few hundred nN, or of larger tissues, with forces greater than 1 mN. Our method supports the mechanical analysis of micro- to meso-scale 3D tissues, such as multicellular spheroids (200-300 μm diameter), by applying forces in the range of sub-hundred nN to sub-mN, while also maintaining a spatial resolution of elasticity measurement as small as 20-30 μm.
View Article and Find Full Text PDFThis study presents novel biocompatible Polydimethylsiloxane (PDMS)-based micromechanical tweezers (μTweezers) capable of the stiffness characterization and manipulation of hydrogel-based organoids. The system showed great potential for complementing established mechanical characterization methods such as Atomic Force Microscopy (AFM), parallel plate compression (PPC), and nanoindentation, while significantly reducing the volume of valuable hydrogels used for testing. We achieved a volume reduction of ~0.
View Article and Find Full Text PDFTraditional microbial detection methods often rely on the overall property of microbial cultures and cannot resolve individual growth event at high spatiotemporal resolution. As a result, they require bacteria to grow to confluence and then interpret the results. Here, we demonstrate the application of an integrated ptychographic sensor for lensless cytometric analysis of microbial cultures over a large scale and with high spatiotemporal resolution.
View Article and Find Full Text PDFIn this paper, we report on a novel biocompatible micromechanical bioreactor (actuator and sensor) designed for the in situ manipulation and characterization of live microtissues. The purpose of this study was to develop and validate an application-targeted sterile bioreactor that is accessible, inexpensive, adjustable, and easily fabricated. Our method relies on a simple polydimethylsiloxane (PDMS) molding technique for fabrication and is compatible with commonly-used laboratory equipment and materials.
View Article and Find Full Text PDFWhole slide imaging (WSI) has moved digital pathology closer to diagnostic practice in recent years. Due to the inherent tissue topography variability, accurate autofocusing remains a critical challenge for WSI and automated microscopy systems. The traditional focus map surveying method is limited in its ability to acquire a high degree of focus points while still maintaining high throughput.
View Article and Find Full Text PDFA variety of engineered nanoparticles, including lipid nanoparticles, polymer nanoparticles, gold nanoparticles, and biomimetic nanoparticles, have been studied as delivery vehicles for biomedical applications. When assessing the efficacy of a nanoparticle-based delivery system, testing with a model delivery system is crucial because it allows for real-time, quantitative transport analysis, which is often difficult with animal models. The advent of tissue engineering has offered methods to create experimental models that can closely mimic the 3D microenvironment in the human body.
View Article and Find Full Text PDFWe report an angle-tilted, wavelength-multiplexed ptychographic modulation approach for multispectral lensless on-chip microscopy. In this approach, we illuminate the specimen with lights at five wavelengths simultaneously. A prism is added at the illumination path for spectral dispersion.
View Article and Find Full Text PDFWe report a new coherent imaging technique, termed ptychographic structured modulation (PSM), for quantitative super-resolution microscopy. In this technique, we place a thin diffuser (i.e.
View Article and Find Full Text PDFMicromachines (Basel)
July 2019
We report on the design and the modeling of a three-dimensional (3D) printed flexure-based actuation mechanism for robotic microtweezers, the main body of which is a single piece of nylon. Our design aims to fill a void in sample manipulation between two classes of widely used instruments: nano-scale and macro-scale robotic manipulators. The key component is a uniquely designed cam flexure system, which linearly translates the bending of a piezoelectric bimorph actuator into angular displacement.
View Article and Find Full Text PDFWe have demonstrated a new method of 3D elastography based on 3D light microscopy and micro-scale manipulation. We used custom-built micromanipulators to apply a mechanical force onto multicellular tumor spheroids (200-300 µm in size) and recorded the induced compression with a differential interference contrast (DIC)/confocal microscope to obtain a 4D (x, y, z, and indentation steps) image sequence. Deformation analysis made through 3D pattern tracking without using fluorescence revealed 3D structural and spatial heterogeneity in tumor spheroids.
View Article and Find Full Text PDFWe have developed a force sensing system to continuously evaluate the mechanical elasticity of micrometer-scale (a few hundred micrometers to a millimeter) live tissues. The sensing is achieved by measuring the deflection of force sensitive cantilevers through microscopic image analysis, which does not require electrical strain gauges. Cantilevers made of biocompatible polydimethylsiloxane (PDMS) were actuated by a piezoelectric actuator and functioned as a pair of chopsticks to measure the stiffness of the specimen.
View Article and Find Full Text PDFStructured illumination has been widely used for optical sectioning and 3D surface recovery. In a typical implementation, multiple images under non-uniform pattern illumination are used to recover a single object section. Axial scanning of the sample or the objective lens is needed for acquiring the 3D volumetric data.
View Article and Find Full Text PDFAnnu Int Conf IEEE Eng Med Biol Soc
July 2018
We investigate the structural cellular alterations in breast cancer spheroids at various growth stages using transmission electron microscopy (TEM), focused ion beam (FIB), and scanning electron microscopy (SEM) imaging. Samples sliced by FIB milling were studied for 3D analysis and construction. The imaging results of different spheroid ages were compared for a better understanding of cancer spheroid models.
View Article and Find Full Text PDF. The use of cerebrospinal shunts is the standard of care for hydrocephalus. However, shunts are extremely vulnerable to failure and lack noninvasive methods to monitor their viability.
View Article and Find Full Text PDFWe propose a novel nondestructive, label-free, mechanical characterization method for composite biomimetic materials. The method combines microscale-force measurement, bright-field microscopy based deformation analysis, and finite-element methods (FEM) to study the heterogeneity in bioengineered composite materials. The method was used to study silk fibroin protein based, donut-shaped scaffolds consisting of a shell (diameter 5 mm) and a core (diameter 2 mm) with a stiff-core or a soft-core configuration.
View Article and Find Full Text PDFWe describe a novel mechanical characterization method that has directly measured the stiffness of cancer spheroids for the first time to our knowledge. Stiffness is known to be a key parameter that characterizes cancerous and normal cells. Atomic force microscopy or optical tweezers have been typically used for characterization of single cells with the measurable forces ranging from sub pN to a few hundred nN, which are not suitable for measurement of larger 3D cellular structures such as spheroids, whose mechanical characteristics have not been fully studied.
View Article and Find Full Text PDFA variety of engineered scaffolds have been created for tissue engineering using polymers, ceramics and their composites. Biomimicry has been adopted for majority of the three-dimensional (3D) scaffold design both in terms of physicochemical properties, as well as bioactivity for superior tissue regeneration. Scaffolds fabricated via salt leaching, particle sintering, hydrogels and lithography have been successful in promoting cell growth and tissue regeneration .
View Article and Find Full Text PDFSpatial light modulator (SLM) is widely used in imaging applications for modulating light intensity and phase delay. In this paper, we report a novel device concept termed angular light modulator (ALM). Different from the SLM, the reported ALM employs a tunable blind structure to modulate the angular components of the incoming light waves.
View Article and Find Full Text PDFA critical consideration for whole slide imaging (WSI) platform is to perform accurate autofocusing at high speed. Typical WSI systems acquire a z-stack of sample images and determine the best focal position by maximizing a figure of merit. This strategy, however, has suffered from several limitations, including low speed due to multiple image acquisitions, relatively low accuracy of focal plane estimation, short axial range for autofocusing, and difficulties in handling transparent samples.
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