Mass-production fabrication of miniaturized plastic chip devices for biochemical applications

A very important aspect in the next stage of genomic research will be the study of genetic diversity originating from an individual, for example, a single nucleotide polymorphism (SNP),. For this, the base-pair sequence needs to be determined quickly and easily; along with effectively gathering the proteins that are produced from the cell and depend on each genetic design. To meet these demands, the use of a miniaturized experimental apparatus formed on a chip is suitable as it gives a very small and well-controlled space to undertake precise analyses. This type of chip device needs to be disposable, inexpensive and of uniform quality, therefore many chips should be fabricated at the same time from a low cost chip material such as plastic. A mass-production fabrication process for such plastic chips was determined as follows. A thick coating type photoresist was spin-coated onto a 4-inch size Si wafer to 20 μm thickness and patterned by UV-lithography. Thick Au structures were embedded into the resist mold by microelectroplating. After removal of the resist, Au fine structures remained and were used as a metal mold for plastic casting. Plastic, polymethylmethacrylate (PMMA), beads were dissolved in acetone and the polymer solution was cast into the metal mold under vacuum heating environment producing many identical plastic chips at a thickness of 1 mm. The size of the chemical reaction channel, one of the device's components, was 50μn in width and 20μm in depth.