The present invention relates to a arrays of nucleic acid and methods of screening these arrays for desired nucleotide sequences. The method includes mixing a hydrogel material with a plasticizer in a compounding apparatus. The elongate tract is drawn through the working channel of the gastroscope by an engagement member, such as snare, which then allows the distal end of the gastroscope to be advanced into the end cap of the feeding tube so that the two can be pulled together into the stomach. The imaging scan uses a half-Fourier technique, for example. In this invention, when the girders have transverse shift under the effect of the wind or other external forces, the movable comb plate and its comb teeth will rotate correspondingly and the comb teeth of the fixed comb plate will also rotate correspondingly, then the broken of the comb teeth will be avoided.