Xuxiang Ni

Novel design for suspension array detection system

This paper presents a novel method for establishing a two-dimensional laminar fluidic suspension array which is analyzed by using time delay integration (TDI) CCD imaging technology in parallel. The method will make suspension array technology (SAT) bear high throughput as well as its flexibility. Basically, bioassays are conducted on the surface of fluorescent-dyed beads. With each bead set (i.e., multiple beads with the same fluorescent signature) having a slightly different fluorescent signature, probes are first attached to a particular bead set and then hybridized with labeled samples or targets. Two different kinds of encoding dyes are excited by red laser (635 nm, 20mw), their emission wave length are 660nm, 720nm, respectively. Fluorescent dye of reporter molecules was excited by green laser (532nm, 20mw), emitted at 580 nm. The liquid sample was pumped into micro-reservoir by a linear motor. As the velocity of liquid sample is so slow (10mm/s) it is easy to form a laminar fluidic field in the middle of the micro-reservoir. In the direction of laser propagation the size of reservoir is 0.1mm so the laminar liquid can be treated as a two-dimensional fluidic plane. The size of detection area depends on size of micro-sphere and CCD imaging area. The three kinds of fluorescence signals were focused by a lens and then split by mirrors. Fluorescence pass through three band-pass filters (±20nm) before collected by three TDI-CCDs respectively. With these high-quality filters the cross-talk between signals was diminished significantly. The analysis speed is about 2x103 micro-spheres per second, which is much higher than that obtained from currently cytometry method (about 102 micro-spheres to the same size micro-spheres).

Optical transfer function for an f-theta lens based confocal fluorescent microarray analyzer

Optical transfer function is widely used to evaluate the imaging performance of an optical system. Combined with confocal scanning technology, f-theta lens can increase the reading speed for microarrays greatly in guarantee of sufficient resolution and fluorescence collection efficiency, compared with micro-array analyzers that adopting mechanical scanning. In this paper, the characteristics of a confocal scanning f-theta objective lens, which was used in micro-array analyzing instrument, were analyzed by means of optical transfer function. In the whole system, laser passed through the f-theta lens, and arrived at the microarray slide where fluorophores were excited. Fluorescence emitting from the micro-array slide was collected by the same f-theta lens, and was captured by a detector. As a laser illumination system, the objective lens had a smaller stop aperture. As a fluorescence collection system, it had a bigger stop aperture. In conclusion, optical transfer function for the whole system, from source to detector, is the combination of that of the laser illumination, a coherent system, and that of the fluorescence collection system, an incoherent system. Uniformity of laser illumination at the micro-array slide was analyzed using optical transfer function during the course of scanning. The influence of aberrations on optical transfer function is given. The simulating results for above characteristics are also presented.

Study on real-time images compounded using spatial light modulator

Image compounded technology is often used on film and its facture. In common, image compounded use image processing arithmetic, get useful object, details, background or some other things from the images firstly, then compounding all these information into one image. When using this method, the film system needs a powerful processor, for the process function is very complex, we get the compounded image for a few time delay. In this paper, we introduce a new method of image real-time compounded, use this method, we can do image composite at the same time with movie shot. The whole system is made up of two camera-lens, spatial light modulator array and image sensor. In system, the spatial light modulator could be liquid crystal display (LCD), liquid crystal on silicon (LCoS), thin film transistor liquid crystal display (TFTLCD), Deformable Micro-mirror Device (DMD), and so on. Firstly, one camera-lens images the object on the spatial light modulators panel, we call this camera-lens as first image lens. Secondly, we output an image to the panel of spatial light modulator. Then, the image of the object and image that output by spatial light modulator will be spatial compounded on the panel of spatial light modulator. Thirdly, the other camera-lens images the compounded image to the image sensor, and we call this camera-lens as second image lens. After these three steps, we will gain the compound images by image sensor. For the spatial light modulator could output the image continuously, then the image will be compounding continuously too, and the compounding procedure is completed in real-time. When using this method to compounding image, if we will put real object into invented background, we can output the invented background scene on the spatial light modulator, and the real object will be imaged by first image lens. Then, we get the compounded images by image sensor in real time. The same way, if we will put real background to an invented object, we can output the invented object on the spatial light modulator and the real background will be imaged by first image lens. Then, we can also get the compounded images by image sensor real time. Commonly, most spatial light modulator only can do modulate light intensity, so we can only do compounding BW images if use only one panel which without color filter. If we will get colorful compounded image, we need use the system like three spatial light modulator panel projection. In the paper, the systems optical system framework we will give out. In all experiment, the spatial light modulator used liquid crystal on silicon (LCoS). At the end of the paper, some original pictures and compounded pictures will be given on it. Although the system has a few shortcomings, we can conclude that, using this system to compounding images has no delay to do mathematic compounding process, it is a really real time images compounding system.

Detecting system based on framing camera for suspension array

High speed imaging technology has been applied on biomedical research for a long history. Suspension array technology is a new generation of biochip, which was widely used in fields of life science and analytical chemistry, and was developed quickly. This study present a detecting system based on framing camera for suspension array. In suspension array microspheres were used as the carrier of bio-probes and microchannels were used as analyzing platform. By pre-dyeing of fluorophores in microbeads, the addressing of microbeads was implemented by optical coden. Bio-probes attached to microbeads were distinguished by intensity of fluorescence. Suspension array was usually detected with flow cytometry serially, which was slow relatively. Then a 2D parallel measurement system based on framing camera for suspension array was established in order to increase the measurement speed. Liquid sample containing microsphere was injected into microchannel by a 100ul syringe connected by a capillary. Microspheres flowing in the microchannel form a 2D layer, which was illuminated freezingly by a pulsed Xenon lamp and imaged by a microscopy objective in parallel. The microfluidic channel was designed and fabricated, which was a rectangle microchannel of 1mm×50um in cross-section. The image was captured by CCD and transmitted into computer by frame grabber. Image was processed to distinguish microspheres extract information from the background. Thus area measurement of suspension array in microchannel was realized. Compared with flow cytometry, this technology increased analyzing rate greatly, which could be thousands of microspheres per second.

Parallel measurement of suspension array by freezing imaging of microspheres

In this paper, a 2D parallel measurement technology for suspension array was presented. Suspension array technology was a new type of biochip, in which microspheres were used as the carrier of bio-probes. It was usually detected by flow cytometry serially. To measure it in parallel, microchannels were used as analyzing platform. Microspheres flowing in the 2D microchannel were freezingly imaged by pulsed Xenon lamp and a microscopy objective in parallel. The image was captured with CCD. The microfluidic channel was designed and fabricated, which was a rectangle microchannel of 1mm x5Oum in cross-section. System performance design was derived. After the selection of CCD, relationship between the limitation of detection and the power of pulsed Xenon lamp was given. System parameter was provided. Some photography of experimental result was presented. Area measurement of suspension array in microchannel was realized. Compared with flow cytometry, this technology increased analyzing rate greatly, which could be thousands of microspheres per second.

Wide microfluidic channel used in suspension biochip detection system

In this paper we describe a new kind of micro fluidic channel used in suspension biochip detection system suitable to area test of the sample that is different from cytometry, which has been fabricated by us. Cytometry is a conventional platform used in suspension biochip technology. At first, our detection system employs a widen micro fluidic channel width of lmm and different depth 50μ, 1OOμ,which is suitable to different size sample flow in the channel instead of the thin pipe used in the cytometry. Secondly suspension array is analyzed by CCD imaging technology in parallel in stead of detection micro beads or protein one by one. The wide micro channels have been fabricated by three ways: laser ablation, chemical etching and mechanical method. The stability of the micro field is a key factor of the biochip detection system when sample flows through the wide micro channel. A novel sample control method to keep the suspension microspheres flow stably throw the test area has been presented.

Research on technique of grating nanometer-subdivision

In this paper, a new system and method of grating nanometer metrology are introduced. The system is made up of light resource, metrological grating, object lens of microscope, electronic-ocular based on CMOS image sensor, and personal computer. Firstly, metrological grating were irradiated by light resource. Secondly, the grating images on electronic-ocular based on CMOS image sensor. Thirdly, electronic-ocular gained the image and trans to the PC by USB. After gained the image, computer converts it to bitmap and processing. There are three steps of the grating subdivision. Firstly, digital image processing is used to set a soft-reticle over the bitmap. Position of the origin in a period is the result we want, and system resolution depends on pixels in a period. Secondly, pixels on gratings border will be calculated, analyzing any pixel coordinate and value, and using statistics and linear function to calculate more precision of the position of border. And thirdly, multi-origins and average effect of grating are used. In this system, higher measuring resolution based on higher quality gratings and clearer imaging system are obtained, and more pixels are processed in arithmetic. In the experiment system, period of grating is 0.02mm, object lens 40~60X, CMOS image sensor pixels, and the resolution of subdivision. Many experiment data have been gained by using this system, and all measuring data are displayed on the screen, in real-time, and automatically recorded in disk. At last, analyzing these data, conclusion of the measuring resolution and precision accuracy is drawn.

Limitation of detection of microarray analyzer based on CCD

The most successful biochip technologies today are flat microarray and suspension microarray. Usually probes are fluorescence labeled. The fluorophores are excited by laser with a special wavelength. Because the fluorescence signal is very weak, it is hard to detect. The limitation of detection (LOD) is an important index of microarray analyzer. The dependence of LOD of flat and suspension microarray analyzer based on CCD and the fluorescent intensity on characters of excitation light optical system and fluorescence collection optical system as well as the parameters of elements system has been analyzed in detail based on the system configuration. A formula of LOD and fluorescence signal intensity depending on those parameters has been established. The study analyzed system limitation of detection (LOD). Also present a formula of minimal detectable fluorescent molecule numbers as the function of each parameter of microarray analyzer based on CCD. Estimated LOD of our suspension microarray detection system is about 7.9 fluorophores/μm2 at exposure time 1s.