Two-dimensional bar codes

Being one of the first two-dimensional bar codes, the symbology has not yet been standardized by any iudustiy. However, it is being considered for coding shipping manifest information. 

Fig. 3. Model for the two-dimensional arrangement of the human erythrocyte glucose transporter in the membrane. Amino acid residues are identified by their single letter code. Solid bars indicate the location of introns in the transporter gene. The regions coloured black are released from the membrane upon tryptic digestion. Shaded segments indicate the probable regions photolabelled by ATB-BMPA (helix 8) and by cytochalasin B (helix 11 and the loop connecting it to helix 10). The circles with heavy outlines indicate the region labelled by lAPS-forskolin (helix 10).

ISO/DIS 15394, Packaging - Bar code and two-dimensional symbols for shipping, transport and receiving labels, 2000. 

Both one- and two-dimensional (2-D) bar coding systems are now available. Of the two, one-dimensional bar oodes have been the most widely used in the clinical laboratory. 

Xiao et al. [87] recently reported laser optical synthesis encoding (LOSC), a technique where a polystyrene-grafted synthetic support contained a two-dimensional laser-etched bar code on a ceramic substrate. Different chemical handles were introduced on the solid support, and a small 27-member oligonucleotide library was encoded and subsequently decoded successfully by a small camera linked to combinatorial software for the automation of sorting/tracking procedures. 

Another example of encoding that does not interfere with chemistry was suggested in 1997 by Xiao and co-workers [38],The coding structure is an inert ceramic plate with a two-dimensional, laser-etched bar code. The encoded plate, which is a 3 mm X 3 mm square, is placed in the center of a laser optical synthesis chip (LOSC). The chip is a 1 cm X 1 cm square made of polypropylene grafted with polystyrene. The smallest possible size of the encoding ceramic plate is 0.5 mm X 0.5 mm. Unfortunately, the bar code cannot be modified during the coursa of the synthesis. 

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