How are DNA arrays produced?

DNA microarrays are produced using three main methods. One method is printing DNA onto glass slides. In this method, DNA sequences, like PCR products or oligonucleotides, are precisely deposited onto glass slides using a robotic device. This is an example of spotted DNA microarrays. Another method is through in situ synthesis of DNA. This process involves creating DNA sequences directly on the glass slide using a technique called photolithography. It allows for the creation of microarrays with thousands of unique DNA sequences directly on the slide. Another method involves using high-density bead arrays. These arrays use color-coded silica beads (each about 3 micrometers in size) which self-assemble into a substrate either on a fiber-optic bundle or a silica slide. The beads are arranged randomly, but evenly, with about 40,000 elements per square millimeter.