In this paper, we describe a new kind of micro fluidic channel used in suspension biochip detection system that is
different from cytometry. The key indexes of the detection system are space resolution and sensitivity, which both
depended on optical system and filtering system. At first, the key factors which have great effect to space resolution have
been analyzed. Secondly the filtering system of suspension array is analyzed. At last the transmission ration curve of the
filters used in our detection system has been tested in detail. The optimization design suspension biochip is also
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.
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.
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 2x10<sup>3</sup> micro-spheres per second, which is much higher than that obtained from currently cytometry method (about 10<sup>2</sup> micro-spheres to the same size micro-spheres).
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/μm<sup>2</sup> at exposure time 1s.
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.