Illustration of a surface plasmon resonance imaging (SPRi) immunoarray being used to detect antibodies (dark purple). Antibodies recognise specific molecules known as antigens. The SPRi array surface holds antigens to the antibody to be detected. Any antibodies in a sample are first captured by magnetic beads (gold spheres). Binding of the antibody to the antigen on the SPRRi changes the refractive index of the array which is picked up by a detector.