Most of the applications of nanotechnology in molecular diagnostics fall under the broad category of biochips/microarrays but are more correctly termed nanochips and nanoarrays.

Nanotechnology-on-a-chip is an extension of microfluidic/lab-on-a-chip technology. Measuring the presence or activity of selected biomolecules using nanomaterials as tags or labels can result in faster, more sensitive and more flexible testing. Lab-on-a-chip technology involves analysis systems that are distinguishable from simple biosensors by virtue of the fact that they can conduct complete or multiple analyses.

Magnetic or metallic nanoparticles, bound to a suitable antibody or biomolecules, can be used to label specific molecules, structures, or microorganisms. Multicoloured optical coding for biological assays can be achieved by embedding different-sized quantum dots into polymeric microbeads. Such spectral coding technologies are expected to open new opportunities for medical diagnostics. DNA “nanomachines” can be also used as biomolecular detectors.

This ability to make chemical and biological information more cheaply available, and faster and easier to obtain, is expected to fundamentally change healthcare, food safety, and law enforcement.