We report a new technique for conducting immuno-diagnostics on a microfluidic platform. Rather than handling fluid reagents against a stationary solid phase, the platform manipulates analyte-coated magnetic beads through stationary plugs of fluid reagents to detect an antigenic analyte. These isolated but accessible plugs are preencapsulated in a microchannel by capillary force. We call this platform microfluidic inverse phase enzyme-linked immunosorbent assay (lIPELISA). lIPELISA has distinctive advantages in the family of microfluidic immunoassay. In particular, it avoids pumping and valving fluid reagents during assaying, thus leading to a lab-on-a-chip format that is free of instrumentation for fluid actuation and control. We use lIPELISA to detect digoxigenin-labeled DNA segments amplified from E. coli O157:H7 by polymerase chain reaction (PCR), and compare its detection capability with that of microplate ELISA. For 0.259 ng ll -1 of digoxigenin-labeled amplicon, lIPELISA is as responsive as the microplate ELISA. Also, we simultaneously conduct lIP-ELISA in two parallel microchannels.