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A global sentiment in early 2022 is that the COVID-19 virus could become endemic just like common cold flu viruses soon. The most optimistic view is that, with minimal precautions, such as vaccination, boosters and optional masking, life... more
A global sentiment in early 2022 is that the COVID-19 virus could become endemic just like common cold flu viruses soon. The most optimistic view is that, with minimal precautions, such as vaccination, boosters and optional masking, life for most people will proceed as normal soon. However, as warned by A. Katzourakis of Oxford University recently, we must set aside lazy optimism, and must be realistic about the likely levels of death, disability and sickness that will be brought on by a 'COVID-19' endemic. Moreover, the world must also consider that continual circulation of the virus could give rise to new variants such as the new BA.2 variant (a subvariant of Omicron) continues to spread across the US and parts of Europe. Data from the CDC is already showing that BA.2 has been tripling in prevalence every two weeks. Hence, globally, we must use available and proven weapons to continue to fight the COVID-19 viruses, i.e., effective vaccines, antiviral medications, diagnosti...
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In vivo, multiple biophysical cues provided by highly ordered connective tissues of the extracellular matrix regulate skeletal muscle cells to align in parallel with one another. However, in routine in vitro cell culture environments,... more
In vivo, multiple biophysical cues provided by highly ordered connective tissues of the extracellular matrix regulate skeletal muscle cells to align in parallel with one another. However, in routine in vitro cell culture environments, these key factors are often missing, which leads to changes in cell behavior. Here, we present a simple strategy for using optical media discs with nanogrooves and other polymer-based substrates nanomolded from the discs to directly culture muscle cells to study their response to the effect of biophysical cues such as nanotopography and substrate stiffness. We extend the range of study of biophysical cues for myoblasts by showing that they can sense ripple sizes as small as a 100 nm width and a 20 nm depth for myotube alignment, which has not been reported previously. The results revealed that nanotopography and substrate stiffness regulated myoblast proliferation and morphology independently, with nanotopographical cues showing a higher effect. These ...
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Research Interests: Engineering, Physics, Materials Science, Optics, Microscopy, and 14 moreNanofabrication, Applied Physics, Photonics, Nanoparticles, Femtosecond Laser, Nanotechnology, Light, Fabrication, Diffraction, Field, Laser processing, Super Resolution Imaging, Electrical And Electronic Engineering, and Nanoscience and nanotechnology
In this paper, we describe a novel and simple process for the fabrication of all-transparent and encapsulated polymeric nanofluidic devices using nano-indentation lithography. First, a nanomechanical probe is used to ‘scratch’ nanoscale... more
In this paper, we describe a novel and simple process for the fabrication of all-transparent and encapsulated polymeric nanofluidic devices using nano-indentation lithography. First, a nanomechanical probe is used to ‘scratch’ nanoscale channels on polymethylmethacrylate (PMMA) substrates with sufficiently high hardness. Next, polydimethylsiloxane (PDMS) is used twice to duplicate the nanochannels onto PDMS substrates from the ‘nano-scratched’ PMMA substrates. A number of experiments are conducted to explore the relationships between the nano-indentation parameters and the nanochannel dimensions and to control the aspect ratio of the fabricated nanochannels. In addition, traditional photolithography combined with soft lithography is employed to fabricate microchannels on another PDMS ‘cap’ substrate. After manually aligning the substrates, all uncovered channels on two separate PDMS substrates are bonded to achieve a sealed and transparent nanofluidic device, which makes the dimensi...
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Nanoscale correlation of structural information acquisition with specific-molecule identification provides new insight for studying rare subcellular events. To achieve this correlation, scanning electron microscopy has been combined with... more
Nanoscale correlation of structural information acquisition with specific-molecule identification provides new insight for studying rare subcellular events. To achieve this correlation, scanning electron microscopy has been combined with super-resolution fluorescent microscopy, despite its destructivity when acquiring biological structure information. Here we propose time-efficient non-invasive microsphere-based scanning superlens microscopy that enables the large-area observation of live-cell morphology or sub-membrane structures with sub-diffraction-limited resolution and is demonstrated by observing biological and non-biological objects. This microscopy operates in both non-invasive and contact modes with ∼200 times the acquisition efficiency of atomic force microscopy, which is achieved by replacing the point of an atomic force microscope tip with an imaging area of microspheres and stitching the areas recorded during scanning, enabling sub-diffraction-limited resolution. Our me...
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Microsphere-assisted microscopy has received a lot of attention recently due to its simplicity and its capability to surpass the diffraction limit. However, to date, sub-diffraction-limit features have only been observed in virtual images... more
Microsphere-assisted microscopy has received a lot of attention recently due to its simplicity and its capability to surpass the diffraction limit. However, to date, sub-diffraction-limit features have only been observed in virtual images formed through the microspheres. We show that it is possible to form real, super-resolution images using high-refractive index microspheres. Also, we report on how changes to a microsphere's refractive index and size affect image formation and planes. The relationship between the focus position and the additional magnification factor is also investigated using experimental and theoretical methods. We demonstrate that such a real imaging mode, combined with the use of larger microspheres, can enlarge sub-diffraction-limit features up to 10 times that of wide-field microscopy's magnification with a field-of-view diameter of up to 9 μm.
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Recent developments in far-field fluorescent microscopy have enabled nanoscale imaging of biological entities by ingenious applications of fluorescent probes. For non-fluorescence applications, however, scanning probe microscopy still... more
Recent developments in far-field fluorescent microscopy have enabled nanoscale imaging of biological entities by ingenious applications of fluorescent probes. For non-fluorescence applications, however, scanning probe microscopy still remains one of the most commonly used methods to "image" nanoscale features in all three dimensions, despite its limited throughput and invasiveness to scanned samples. Here, we propose a time-efficient three-dimensional super-resolution microscopy method: near-field assisted white light interferometry (NFWLI). This method takes advantage of topography acquisition using white-light interferometry and lateral near-field imaging via a microsphere superlens. The ability to discern structures in central processing units (CPUs) with minimum feature sizes of approximately 50 nm in the lateral dimensions and approximately 10 nm in the axial dimension within 25 s (40 times faster than atomic force microscopes) was demonstrated. We elaborate in this p...
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Research Interests: Engineering, Electrical Engineering, Computer Science, Materials Science, Circuits and Systems, and 15 morePower Management, Induction Generators, Energy Harvesting, Power Generation, Copper, Electromagnetic Induction, Frequency, Low Power, Low Power Electronics, Circuits, Infrared, Electric Power, Hz, Laser Micromachining, and Mechanical Energy
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Research Interests: Electrical Engineering, Computer Science, Distributed Computing, Power Electronics, Vibrations, and 13 moreVibration, Transducers, Power Generation, Capacitor, Wireless Sensor, Voltage, Human Movement, Integrated Circuit, Voltage Multiplier, Transducer, Intelligent Sensors, Commercial Off-The-Shelf, and Form Factor
We report here an approach to rapidly construct organized formations of micron-scale pillars from a thin polydimethylsiloxane (PDMS) film by optically induced electrohydrodynamic instability (OEHI). In OEHI, a heterogeneous electric field... more
We report here an approach to rapidly construct organized formations of micron-scale pillars from a thin polydimethylsiloxane (PDMS) film by optically induced electrohydrodynamic instability (OEHI). In OEHI, a heterogeneous electric field is induced across two thin fluidic layers by stimulating a photoconductive thin film in a parallel-plate capacitor configuration with visible light. We demonstrated that this OEHI method could control nucleation sites of pillars formed by electrohydrodynamic instability. To investigate this phenomenon, a tangential electric force component is assumed to have arisen from the surface polarization charge and is introduced into the traditional perfect dielectric model for PDMS films. Numerical simulation results showed that this tangential electric force played an important role in OEHI.
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We present a multipoint “virtual dispenser” to draw femtolitre droplets from a dielectric fluidic thin film using pulse-voltage-triggered optically induced electrohydrodynamic instability (PVT-OEHI). The “virtual dispenser” generates... more
We present a multipoint “virtual dispenser” to draw femtolitre droplets from a dielectric fluidic thin film using pulse-voltage-triggered optically induced electrohydrodynamic instability (PVT-OEHI). The “virtual dispenser” generates instability nucleation sites by controlling the optically induced lateral electrical stress and thermocapillary flow inside an optoelectronics chip. A time scale analysis shows that the electrohydrodynamic (EHD) instability phenomenon is present; however, its external manifestation is suppressed by OEHI. We observed two droplet dispensing mechanisms which correspond to different EHD states: Taylor cone formation and optically induced EHD jet. The EHD states transition could be realized by adjusting the pulse voltage parameters to alter the morphology of dispensed micron-scale polymer droplets, which could then be formed into organized arrays of microlenses with controllable diameter and curvature based on surface tension effect.
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Optoelectrokinetics chip improves efficiency and sensitivity of detecting peritoneal metastasis in gastric cancer.
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Research Interests: Engineering, Physics, Materials Science, Microfluidics, Nanoparticle, and 15 moreApplied Physics, Lab On A Chip, Nanotechnology, Induced-Charge Electrokinetics Microfluidics, Dielectrophoresis, DNA, Assembly, Manipulation, Fabrication, Field, Electrokinetic Phenomena, Cells, Electrical And Electronic Engineering, Ions, and Nanoscience and nanotechnology
Our group has reported that Melan-A cells and lymphocytes undergo self-rotation in a homogeneous AC electric field, and found that the rotation velocity of these cells is a key indicator to characterize their physical properties. However,... more
Our group has reported that Melan-A cells and lymphocytes undergo self-rotation in a homogeneous AC electric field, and found that the rotation velocity of these cells is a key indicator to characterize their physical properties. However, the determination of the rotation properties of a cell by human eyes is both gruesome and time consuming, and not always accurate. In this paper, a method is presented to more accurately determine the 3D cell rotation velocity and axis from a 2D image sequence captured by a single camera. Using the optical flow method, we obtained the 2D motion field data from the image sequence and back-project it onto a 3D sphere model, and then the rotation axis and velocity of the cell were calculated. After testing the algorithm on animated image sequences, experiments were also performed on image sequences of real rotating cells. All of these results indicate that this method is accurate, practical, and useful. Furthermore, the method presented there can also...
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Cell membrane capacitance and conductance are key pieces of intrinsic information correlated with the cellular dielectric parameters and morphology of the plasma membrane; these parameters have been used as electrophysiological biomarkers... more
Cell membrane capacitance and conductance are key pieces of intrinsic information correlated with the cellular dielectric parameters and morphology of the plasma membrane; these parameters have been used as electrophysiological biomarkers to characterize cellular phenotype and state, and they have many associated clinical applications. Here, we present our work on the non-invasive determination of cell membrane capacitance and conductance by an optically activated microfluidics chip. The model for determining the cell membrane capacitance and conductance was established by a single layer of the shell-core polarization model. Three-dimensional finite-element analyses of the positive and negative optically induced dielectrophoresis forces generated by the projected light arrays of spots were performed, thus providing a theoretical validation of the feasibility of this approach. Then, the crossover frequency spectra for four typical types of cells (Raji cells, MCF-7 cells, HEK293 cells...
Research Interests: Biophysics, Chemistry, Dielectrophoresis, Biological Sciences, Finite Element Analysis, and 15 moreHumans, Computer Simulation, Frequency, Conductance, CHEMICAL SCIENCES, Electrorotation, Electrophoresis, Capacitance, Exhibit, Cancer cells, Electric Field, Cytoplasm, Electric Conductivity, Electric Capacitance, and Cell Membrane
The synthesis and assembly of components are key steps in micro/nano device manufacturing. In this article, we report an optically controlled assembly method that can rapidly pattern micro/nano devices by directly assembling ions and... more
The synthesis and assembly of components are key steps in micro/nano device manufacturing. In this article, we report an optically controlled assembly method that can rapidly pattern micro/nano devices by directly assembling ions and nanomaterials without expensive physical masks and complex etching processes. Utilizing this controllable process, different types of device components (e.g., metallic and semiconductor) can be fabricated and assembled in 10-30 seconds, which is far more rapid and cost-effective than any other micro/nano fabrication method.
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Research Interests: Computer Science, Materials Science, Technology, Microfluidics, Nanotechnology, and 14 moreMedicine, Rapid Prototyping, Polymer, Microfabrication, Manipulation, Particles, Photolithography, Fabrication, Lithography, Tissue, Science Technology, Polydimethylsiloxane, Microlens, and Nanoscience and nanotechnology
We present a new digitally controlled, optically induced electrochemical deposition (OED) method for fabricating silver nanostructures. Projected light patterns were used to induce an electrochemical reaction in a specialized... more
We present a new digitally controlled, optically induced electrochemical deposition (OED) method for fabricating silver nanostructures. Projected light patterns were used to induce an electrochemical reaction in a specialized sandwich-like microfluidic device composed of one indium tin oxide (ITO) glass electrode and an optically sensitive-layer-covered ITO electrode. Silver polyhedral nanoparticles, triangular and hexagonal nanoplates, and nanobelts were controllably synthesized in specific positions at which projected light was illuminated. The silver nanobelts had rectangular cross-sections with an average width of 300 nm and an average thickness of 100 nm. By controlling the applied voltage, frequency, and time, different silver nanostructure morphologies were obtained. Based on the classic electric double-layer theory, a dynamic process of reduction and crystallization can be described in terms of three phases. Because it is template- and surfactant-free, the digitally controll...
Research Interests: Materials Science, Electrochemistry, Crystallization, Nanotechnology, Medicine, and 13 moreOne dimensional nanostructures, Fabrication, Nanostructure, Interface, Metals, Science Technology, Devices, Multidisciplinary Sciences, Electrode, Nanobelts, Potential Applications, ARRAYS, and Indium tin oxide
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Single-cell density and mass were measured rapidly using a combination of optically induced electrokinetics, microfluidics, computer vision, and classical sedimentation theory.