English: FSL constructs can be printed with a standard desktop inkjet printer directly onto paper to create immunoassays. Image is a typical example of an inkjet printed enzyme immunoassay (EIA) where 12 different FSL constructs were printed as identifying codes on paper and then reacted against different samples. The antibody activity in the samples can be identified by appearance of words identifying the target antigen.

An empty inkjet cartridge is filled with an FSL construct and words, barcodes, or graphics are printed. A Perspex template is adhered to the surface to create reaction wells. The method is then a standard EIA procedure, but blocking of serum is not required and undiluted serum can be used.

A typical EIA procedure is as follows: add serum, incubate, wash by immersion, add secondary EIA detection antibody, incubate, wash, add NBT/BCIP precipitating substrate and stop the reaction when developed by washing. The end result is stable for years.