A key challenge when imaging whole biomedical specimens is how to quickly obtain massive cellular information over a large field of view (FOV). We report a subvoxel light-sheet microscopy (SLSM) method enabling high-throughput volumetric imaging of mesoscale specimens at cellular resolution. A nonaxial, continuous scanning strategy is developed to rapidly acquire a stack of large-FOV images with three-dimensional (3-D) nanoscale shifts encoded. Then, by adopting a subvoxel-resolving procedure, the SLSM method models these low-resolution, cross-correlated images in the spatial domain and can iteratively recover a 3-D image with improved resolution throughout the sample. This technique can surpass the optical limit of a conventional light-sheet microscope by more than three times, with high acquisition speeds of gigavoxels per minute. By fast reconstruction of 3-D cultured cells, intact organs, and live embryos, SLSM method presents a convenient way to circumvent the trade-off between mapping large-scale tissue (>100 mm3) and observing single cell (∼1-μm resolution). It also eliminates the need of complicated mechanical stitching or modulated illumination, using a simple light-sheet setup and fast graphics processing unit-based computation to achieve high-throughput, high-resolution 3-D microscopy, which could be tailored for a wide range of biomedical applications in pathology, histology, neuroscience, etc.
Biological systems contain a multitude of molecules with specific functions and three-dimensional shapes that enable
them to selectively interact with other molecules in a coordinated fashion. Engineering, on the other hand, has produced
devices that operate on the micron-scale and that combine electronic and mechanical systems. Microelectromechanical
Systems (MEMS) offer advantages such as the integration of a variety of functions into a single device (i.e. "lab-on-a-chip"
platforms) and portability for "point-of-care" diagnostics. This study utilizes a microscale electrochemical sensor
for detecting BoNT apatamer hybridization, in which we first used top-down lithographic processing to define the
pattern of the electrodes and then used bottom-up manufacturing to modify the surface molecular properties for reducing
The goal was to systemically examine the effects of the design parameters of an electrochemical DNA sensor. Four key
design parameters were examined: the area of the working electrode, the area of the counter electrode, the separation
distance between the working and counter electrodes, and the overlap length between the working and counter
electrodes. Through a log-log analysis of the current generated, representing the signal or noise, across variations of the
different parameters, the significance of each parameter in sensor performance was determined. We found that the area
of the working electrode was important in the performance optimization of the sensor, while the performance seemed to
be independent of the other three parameters. The output signal level increased with the area of the working electrode
and the signal-to-noise ratio was about constant in the tested range.
Current microfabrication technologies rely on top-down, photolithographic techniques that are ultimately
limited by the wavelength of light. While systems for nanofabrication do exist, they frequently suffer from
high costs and slow processing times, creating a need for a new manufacturing paradigm. The combination
of top-down and bottom-up fabrication approaches in device construction creates a new paradigm in micro- and
nano-manufacturing. The pre-requisite for the realization of the manufacturing paradigm relies on the
manipulation of molecules in a deterministic and controlled manner. The use of AC electrokinetic forces,
such as dielectrophoresis (DEP) and AC electroosmosis, is a promising technology for manipulating nano-sized
particle in a parallel fashion. A three-electrode micro-focusing system was designed to expoit this
forces in order to control the spatial distribution of nano-particles in different frequency ranges. Thus far, we
have demonstrated the ability to concentrate 40 nm and 300 nm diameter particles using a 50 μm diameter
focusing system. AC electroosmotic motion of the nano-particles was observed while using low frequencies
(in a range of 30 Hz - 1 KHz). By using different frequencies and changing the ground location, we have
manipulated the nano-particles into circular band structures with different width, and focused the nanoparticles
into circular spots with different diameters. Currently, we are in the progress of optimizing the
operation parameters (e.g. frequency and AC voltages) by using the technique of particle image velocimetry
(PIV). In the future, design of different electrode geometries and the numerical simulation of electric field
distribution will be carried out to manipulate the nano-particles into a variety of geometries.
We present a one-step replication technique for optical gratings that allows the control of the corrugation height and period. By using an ink that slowly condenses into a multilayer polymer, it is possible to control the corrugation height by changing the condensation time. In addition, by applying a mechanical strain on the stamp, it is also possible to change the period of the grating. The combination of these two features added to the ease of use and low cost of this technique makes it very attractive for the fast prototyping of optical gratings for applications such as the measurement of surface plasmon band gaps. Corrugation heights in the range of 100 to 250 nm and period variations up to 10% are achieved.
Blood analysis provides vital information for health conditions. For instance, typical infection response is correlated to an elevated White Blood Cell (WBC) count, while low Red Blood Cell (RBC) count, hemoglobin and hematocrit are caused by anemia or internal bleeding. We are developing two essential modules, deionization (DI) chip and microfluidic cytometer with impedance spectroscopy flow, for enabling the realization of a single platform miniaturized blood analyzer.
In the proposed analyzer, blood cells are preliminarily sorted by Dielectrophoretic (DEP) means into sub-groups, differentiated and counted by impedance spectroscopy in a flow cytometer. DEP techniques have been demonstrated to stretch DNA, align Carbon Nanotubes (CNT) and trap cells successfully. However, DEP manipulation does not function in biological media with high conductivity. The DI module is designed to account for this challenge.
H Filter will serve as an ion extraction platform in a microchamber. Sample and buffer do not mix well in micro scale allowing the ions being extracted by diffusion without increasing the volume. This can keep the downstream processing time short.
Micro scale hydrodynamic focusing is employed to place single cell passing along the central plane of the flow cytometer module. By applying an AC electrical field, suspended cells are polarized, membrane capacitance C<sub>m</sub>, cytoplasm conductivity σ<sub>c</sub>, and cytoplasm permittivity ε<sub>c</sub> will vary as functions of frequency. Tracing back the monitored current, the numbers of individual cell species can be evaluated.
The advance of micro and nanodevice manufacturing technology enables us to carry out biological and chemical processes in a more efficient manner. In fact, fluidic processes connect the macro and the micro/nano worlds. For devices approaching the size of the fluid molecules, many physical phenomena occur that are not observed in macro flows. In this brief review, we discuss a few selected topics which of are interest for basic research and are important for applications in biotechnology.
By using distributed arrays of micro-actuators as effectors, micro-sensors to detect the optimal actuation location, and microelectronics to provide close loop feedback decisions, a low power control system has been developed for controlling a UAV. Implementing the Microsensors, Microactuators, and Microelectronics leads to what is known as a M<SUP>3</SUP> (M-cubic) system. This project involves demonstrating the concept of using small actuators (approximately micron-millimeter scale) to provide large control forces for a large-scale system (approximately meter scale) through natural flow amplification phenomenon. This is theorized by using fluid separation phenomenon, vortex evolution, and vortex symmetry on a delta wing aircraft. By using MEMS actuators to control leading edge vortex separation and growth, a desired aerodynamic force can be produced about the aircraft for flight control. Consequently, a MEMS shear stress sensor array was developed for detecting the leading edge separation line where leading edge vortex flow separation occurs. By knowing the leading edge separation line, a closely coupled micro actuation from the effectors can cause the required separation that leads to vortex control. A robust and flexible balloon type actuator was developed using pneumatic pressure as the actuation force. Recently, efforts have started to address the most elusive problem of amplified distributed control (ADC) through data mining algorithms. Preliminary data mining results are promising and this part of the research is ongoing. All wind tunnel data used the baseline 56.5 degree(s) sweepback delta wing with root chord of 31.75 cm.
Micro riblets have been designed and fabricated by surface- micromachining technology with 3-layer polysilicon and 2-layer PSG. The riblets with rib-peak-widths of 3, 4, 6 micrometers and spacings of 100 micrometers and 300 micrometers have been chosen. Several more complicated surface patterns like fish scale replica, have also been designed. On the same chip, the micromachined hot film shear stress sensor with different geometries (6 X 100, 12 X 100, 18 X 100 micrometers <SUP>2</SUP>, etc.) are integrated downstream from the micro riblets. The sensors are made of polysilicon and used for the shear stress measurement of the fluid flowing over micro riblets.
Recent development of silicon micromachining technology has made possible the fabrication of many micromechanical devices. Applications of these micromechanical devices are many, but their use for smart structures and materials has just begun. Here, an updated report on the development of a drag-reducing smart skin is given. In order to facilitate the fabrication of the smart skin, we have first developed a new sacrificial-layer etching model for etching phosphosilicate-glass using hydrofluoric acid. This model then leads to the development of two key devices for the skin, including a shear-stress sensor and a magnetic microactuator.