Here we achieved record-high >500 volumes/second two-photon imaging by improving lateral and axial scanning speed via 32-channel multifocal excitation/detection, and a tunable acoustic gradient-index lens, respectively. We developed a deconvolution process to reduce scattering-induced crosstalk in multifocal detection scheme, thus enabling whole brain imaging of Drosophila with millisecond and micrometer spatiotemporal resolution. Potential applications toward brain science include studying millisecond dynamics in a neuronal network, and resolving 3D microfluidics in blood vessels.
To monitor the healthiness of cells, it is very important to develop quick ways to characterize cells with the diseased and normal mitochondria. Thus, we can take measures to prevent potential development of mitochondria-related diseases. Physical study and systemic proof of concept by engineering method to perform quick diagnosis of the normal and diseased mitochondria have not been well achieved yet. In this study, we used insulator dielectrophoresis (i-DEP), by utilizing the intrinsic dielectric response of a cell to an external AC electric field to differentiate cells containing partially diseased and normal mitochondria to test if we can select diseased mitochondria-containing cells but not the normal cells. We found that it is possible to detect the diseased and healthy mitochondria in cells without breaking the cell membrane. Taking advantage of the dielectrophoresis, DEP principle, we may develop a quick diagnostic method to detect diseased mitochondria in living cells.
Studying neuronal connections and activities in vivo is critical for understanding the brain. Optical microscopy, with the capability of specific fluorescent labeling and sub-cellular spatial resolution, has become an indispensable tool in neuroscience. However, the major limitation of optical imaging is penetration depth and imaging speed to capture neural signal dynamics in deep brain regions. Recently, by applying adaptive optics, high-energy laser, or long wavelength lasers for nonlinear imaging, penetration depth around 1mm has been achieved in living mouse brains. Nevertheless, this depth barely pierces through the mouse cortex and is far from reaching the bottom of the centimeter-thick mouse brain. For studying deeper regions of the brain, brain slice is one possible approach, yet it is invasive and cut away many neuron connections. In this study, a home-built two-photon microscope is integrated with both a gradient refractive index (GRIN) lens and a tunable acoustic gradient (TAG) lens. The GRIN lens serves as a micro-endoscope which extends the imaging depth to a centimeter while minimizing the invasiveness, and the TAG lens provides ~100kHz axial scanning which enables high-speed volumetric imaging of neuronal response. This novel high-speed volumetric endoscopy system offers an unprecedented opportunity towards studying three-dimensional neuronal dynamics in deep brains regions of a living mouse.
We combine pulsed laser, supercontinuum radiation source and fast single-photon counting peripherals to obtain a multifunctional
micro/nano-scope. This provides us with better spatial and temporal resolution to observe fast dynamics.
Performing fluorescence correlation spectroscopy for fast dynamics (<μs) with sub-diffraction limit resolution to observe
the initial state of single-lipid dynamics in supported lipid bilayers and living cells is our goal. Lipid raft serves as a
platform for recruiting signaling components of effective signal transduction. However, the dynamics of sub-200nm
rapidly aggregated lipid rafts are still not elucidated in living cells. We here report our recent progress on the
construction of this multi-functional stage-scanning fluorescence micro/nanoscope for single-lipid dynamics study.
Zero-mode waveguides (ZMWs) are optical nanostructures to confine fluorescent excitation within sub-diffraction
volumes and are commonly used for single-molecule analysis. However, the conventional ZMWs with aluminum film on
fused silica have limitations on living cell studies. The same surfaces composed of hydroxyl group inside and outside
each ZMW restrict specific surface functionalization. The sharp-cylinder shaped and rough edge of each ZMW produces
a steric interference of molecular dynamics on cell membrane. In this study, selectively surface functionalization inside
and outside of each ZMW was achieved with tri-metal-layer film on fused silica. Moreover, bowl-shaped and smooth edge of each ZMW was manufactured in large area. The improvement of ZMWs provides a broad way for monitoring molecular dynamics in living cells.
We report for the first time the use of orientation dependent etching (ODE) of (110) c-Si in sidewall thin film technology for imprint mask fabrication with low line edge roughness (LER) over a large area. Oxidation is used for sidewall thin film formation with a good critical dimension control. 2-dimensional oxidation effects are discussed. Features down to 12 nm have been fabricated successfully. Simulation shows that the fabricated oxide line is strong enough to imprint both thermoplastic and photo-curable imprint resists.
We report our fabrication of nanoscale devices using electron beam and nanoimprint lithography (NIL). We focus our study in the emerging fields of NIL, nanophotonics and nanobiotechnology and give a few examples as to how these nanodevices may be applied toward genomic and proteomic applications for molecular analysis. The examples include reverse NIL-fabricated nanofluidic channels for DNA stretching, nanoscale molecular traps constructed from dielectric constrictions for DNA or protein focusing by dielectrophoresis, multi-layer nanoburger and nanoburger multiplets for optimized surface-plasma enhanced Raman scattering for protein detection, and biomolecular motor-based nanosystems. The development of advanced nanopatterning techniques promises reliable and high-throughput manufacturing of nanodevices which could impact significantly on the areas of genomics, proteomics, drug discovery and molecular clinical diagnostics.
Nano optical biosensors employ the interaction between biomolecules and light confined in nanometer scale structures to report the bio-recognition events. This small scale sensing area/volume can ensure that small amount of biorecognition events could be detected. The exceptional sensitivity and high spatial density of nano optical biosensors make them unique in practical applications in nucleic acid detection. Lab-on-a-Chip systems provide the capabilities of separation, cell lysing, polymerase chain reaction (PCR), allowing finishing bio agent detection processes on a chip. In this paper, we present our recent efforts on integrating some novel nanooptical biosensors into Lab-on-a-Chip systems and some preliminary test results.
Magnetohydrodynamic (MHD) pumping has several attractive features including no-moving-parts operation, compatibility with biological solutions, and bi-directional pumping capability. In this work, a re-circulating ceramic MHD micropump is described. The MHD operation principle is based on the generation of Lorenz forces on ions within an electrolytic solution by means of perpendicular electric and magnetic fields. These Lorenz forces propel the ions through a channel, thus creating a net flow with no moving parts. Fabrication of the pumps is achieved by means of a new ceramic MEMS (CMEMS) platform in which devices are built from multiple layers of green-sheet ceramics. The major advantage to this technology is that unlike many other fabrication technologies, the multi-layer ceramic CMEMS platform is truly three-dimensional, thus enabling the building of complex integrated systems within a single platform. The ceramic-based MHD pumps have been analyzed and tested using both finite element modeling and experimental validation. Test results indicate that the pumps are capable of pumping a wide range of biological fluids in the flow rate range of microliters per minute. Additionally, good stability over 24 hours and good correlation with modeling data have been verified.
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