By simultaneously scanning for thousands of genes or proteins in a biological sample, doctors could diagnose many diseases in a single step. But today's DNA or protein microarrays are too expensive for widespread clinical use, in part because their manufacture is a complex, multistep process.

A potentially cheaper tool for detecting telltale DNA and proteins appears on this page: capsule-shaped polymer particles, each 180 micrometers long. Each particle can be loaded with a specific biomole­cule so that one half of the particle fluoresces when it detects a disease target. Imprinted with bar-code-like patterns of holes, the particles can be read optically; they could serve as detectors for more than a million distinct biological targets. Technicians with the right optical equipment could, in theory, mix the particles with a sample and read off the results.