A novel broadband high-speed impedance spectrometer has been developed for the analysis of single biological particles in a high-throughput microfluidic cytometer. The technique is based on obtaining the impulse response of the system using maximum length sequences (MLS) as the excitation signal. The impulse response is converted into the frequency domain using Fast Fourier Transform (FFT). Theoretical modeling and simulation of a single cell suspended in the cytometer show that the MLS technique is capable of high precision single particle analysis.
Microfluidic analysis devices, often referred to as Micro Total Analysis Systems or the Lab-on-a-chip, are often based on the manipulation of small volumes of fluid. These devices require the design and fabrication of components for fluid handling, control and measurement, such as micropumps, micromixers and flow sensors. The fabrication of miniature versions of large scale components such as pressure sensors and flow rate meters has been demonstrated. However, complicated fabrication is prohibitive and devices which involve flow constriction can be prone to blocking if particle containing samples are used. This paper presents results of the design and fabrication of a microimpedance measurement cell, designed to measure the impedance of sub-nanolitre volumes of fluids. The measurement system was designed to measure the electrical impedance at several different frequencies, allowing identification and analysis of the material contained within the sample volume. Measurements of different fluids at different flow rates through a microchannel containing the measurement cell are presented. The use of this system as a solid state flow rate sensor is then discussed.
Block copolymers (BCPs), which self-assemble into spatially periodic one-dimensional (1D) ordered lamellar equilibrium structures, can be used as multilayer waveguide materials. In this article, the hybrid modal characteristics of three representative self-assembled BCPs multilayer stripe waveguides were studied with compact 2D finite-difference time-domain (2D-FDTD) method. By comparing our numerical results with those obtained by the N-layer waveguide formalism, it is found that on some occasions the two-dimensional (2D) formalism is a good choice to substitute for the three-dimensional (3D) modal analysis of multilayer waveguide . It is also been proved that if the sequence of the two different index layers is inverted in the structure, the modal analysis results change dramatically and the lamellar width is an important factor that influences the optical field distribution of the waveguide modes. An investigation about the triblock copolymer (tri-BCP) waveguide revealed that its field distribution layered more obviously for the particularity of tri-BCP waveguide core structure.
An effective way of constructing an AWG with a wide passband is to use a configuration with a parabolic horn as the input waveguide to a slab waveguide. This configuration provides good passband control ability and fabrication stability. However, the parabolic waveguide horn may induce chromatic dispersion (CD) in AWGs. In this paper, first the theory of broadening passband and origins of CD in AWG were analyzed, then the influences of the configuration parameters of parabolic horn to broaden spectrum of AWG were discussed through a beam propagation method (BPM) and numerical calculation. A good flat-top AWG was obtained by choosing rationally three parameters: exit width W, broadening coefficient α and length of multimode waveguide. And low CD was achieved through adjusting the length of multimode waveguide slightly.