Nanowire chemical detector. Light micrograph of a chemical detector using nanotechnology. It can be used to test for raised levels of PSA (prostate specific antigen) in blood, a sign of prostate cancer. The wire runs horizontally between two of the four contacts at centre. The nanowire, some 10 nanometres wide, is covered with antibodies to which PSA binds. If PSA is present in the blood it will bind to the antibodies on the wire, changing the wire's conductivity. This registers as an electrical signal, indicating the presence of PSA. Prostate cancer affects many men in middle age. Early diagnosis increases the chances of curing it. Magnification unknown.