Microflow cytometry has become an attractive tool for counting and analysis of complex cell population and finds many applications in life science research. However, its implementation in screening small sized targets, such as microorganisms, is limited by challenges associated with sample handling and detection in a flow. Here, we report the function of a 3D flow focusing microfluidic system as a high performance, multi-parameter flow cytometry. The system consists of a detection chamber that can precisely control a highly focused sample flow in 3D and an integrated optical fiber to collect the scattered light at the vertical plane. The ability of the system to detect small beads (1 µm), differentiate subtle differences (2 µm) and accurately profile a mixed bead population is demonstrated. Furthermore, multiple types of information about the sample, including the inherent biochemical information (e.g., fluorescence or Raman signal) and physical properties (e.g., size) are simultaneously generated, allowing sophisticated cellular analysis. Together with the facile and robust operation, this provides a versatile tool that could be used for multi-parametric analyses in a diversity of applications.
Autologous chondrocyte transplantation (ACT) has become a promising method for repairing large articular defects. However, dedifferentiation of chondrocytes during cell expansion remains a major limitation for ACT procedures. In this study, we explore the potential of confining cell shape for re-differentiation of dedifferentiated bovine chondrocytes. A novel culture system, combining 2D micropatterning with 3D matrix formation, was developed to control and maintain individual chondrocyte’s shape. Both collagen II synthesis and the mechanical properties of cells were monitored during re-differentiation. We show that a spherical morphology without cell spreading plays a limited role in induction of re-differentiation. Instead, isolated, dedifferentiated chondrocytes partially regain chondrogenic properties if they have an appropriate cell shape and limited spreading.
With non-invasive properties and high sensitivities, portable optical biosensors are extremely desirable for point-of-care (POC) applications. Lab-on-a-chip technology such as microfluidics has been treated as an ideal approach to integrate complex sample processing and analysis units with optical detection elements. The work in this paper has developed an integrated dispersive component in combination with a microfluidic chip, providing a portable and inexpensive platform for on-chip spectroscopic sensing. We demonstrate an integrated microfluidic spectroscopic sensor by using an arrayed waveguide grating (AWG) device. In particular, a visible AWG device (λc=680nm) with chip size of 12.1mm by 1.5mm was designed and fabricated by employing flamed hydrolysis deposited (FHD) silica as the waveguide material. A straight input waveguide is used to perform device characterization while a perpendicular curved waveguide is employed to introduce laser excitation light. A polymer microfluidic chip is integrated with the AWG device by oxygen plasma bonding. To prove effectiveness of the integrated spectroscopic sensor, fluorescence spectrum of an organic fluorophore (Cy5) was tested. Reconstructed spectrum by using the AWG device is compared with the outcome from a conventional spectrometer and a good consistency is presented.
High performance terahertz (THz) radiation sources hold great promise for a variety of military and space applications.
With micro-electro-mechanical systems (MEMS) fabrication techniques, it is possible to attain the smaller, more
precisely machined resonant structures required by Vacuum Electronic Devices (VEDs) to function in these frequencies.
The research presented here proposes a design and fabrication process for a micro-klystron with a targeted operating
frequency of 200 GHz; being developed jointly by Duke University, the University of Strathclyde, UK, and Logos
Technologies. It also analyzes the use of a pseudospark (PS) discharge as a novel electron beam source to drive the
klystron. Dimensional tolerances are investigated using both analytic and numeric techniques. The incorporation of
alignment structures into the fabrication process that utilize kinematic and elastic averaging effects, along with clever
stacking techniques, allows submicron alignment tolerances yielding an expected power output of approximately 5W per
klystron with an overall efficiency of 20%. The device proposed here, with a volume on the order of 0.01 cc, should be
capable of output power densities of up to 1kW/cc. A fabrication run recently completed at MIT's Microsystems
Technology Laboratories yielded promising results and 32 silicon die were successfully bonded into a stack 1.4cm tall.
Difficulties remain, however, in controlling surface roughness and integrating a klystron with alignment features for
parallel processing. Several alternative fabrication schemes have been proposed and another fabrication run based on
these modifications is currently underway.
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