Fluid elements--a concept for automation of diagnostic tests.

Constructs consisting of a channel, a membrane, and an absorber are designed for autonomously carrying out various liquid-handling functions of analytical tests. These so-called fluid elements can be used to set up various circuits for conducting several kinds of analytical tests. To demonstrate the feasibility of this concept, we constructed such a circuit and used it to perform, with two handling steps, an ELISA of hepatitis B surface antigen. The detection limit of the assay was comparable with those of state-of-the-art ELISAs for screening blood, and results could be obtained within a total test time of 20 min. We anticipate that this concept of automation may also serve as a basis for new, highly simplified immunoanalyzers.