Microplate Reader

Overview

A microplate reader measures an optical signal from every well of a microplate, a plastic tray of 96, 384 or more tiny cups, so a lab can assay hundreds of samples in one short run. It is the backbone of high-throughput biology: ELISA tests for antibodies, enzyme kinetics, cell viability, protein and DNA quantitation, drug screening. The plate is the standard unit of work, and the reader is the machine that turns a tray of liquid into a grid of numbers.

A multimode reader covers the three common ways a well can report a result. Absorbance measures how much light a coloured solution blocks. Fluorescence excites a dye and reads the light it re-emits. Luminescence reads light a chemical reaction makes on its own, with no source at all. One instrument switches between them under software control.

How it works

The plate rides into the instrument on the Plate Transport Stage, a motorized XY stage that steps each well precisely under the read head. Two ball-screw drives move it along the rows and columns while home sensors fix the origin, so a 384-well plate is addressed without the operator touching it.

Light is shaped by the Optical System. A xenon flash lamp supplies broadband light for absorbance and excitation, while bandpass filters in the Filter Wheel or a tunable monochromator pick the wavelengths each assay needs; fiber optics carry the light down to the well and emission back up.

Each mode has its own detection path. The Absorbance Module passes a beam straight down through the well and reads the survivors on a photodiode, the basis of an ELISA plate. The Fluorescence Module excites the sample and reads the redshifted glow on a sensitive photomultiplier, with a dichroic separating the two. For glow assays the Luminescence Module darkens the source and simply counts the photons the reaction emits, shielded from its neighbours by a light shroud. The Control Electronics sequence the stage, optics and detectors and integrate each well, streaming the plate map to the host software the moment the read finishes.