Flow Cytometer Product

Overview

A flow cytometer measures physical and chemical properties of single cells or particles as they flow in a fluid stream past one or more laser beams. Each cell scatters light and, if labeled with fluorescent antibodies or dyes, re-emits light at longer wavelengths. By recording several optical signals per cell at rates of tens of thousands per second, the instrument builds a statistical picture of a heterogeneous population: cell size, granularity, and the presence and quantity of specific surface or intracellular markers. It is a core tool in immunology, hematology, cancer research, and microbiology.

The central principle is that single cells must be interrogated one at a time at a fixed, well-lit point. Achieving this requires confining the sample to a thin central thread, illuminating that thread with tightly focused light, and collecting the resulting scatter and fluorescence with enough optical separation to tell signals apart.

Construction

Single-file presentation is the job of the Fluidics & Flow Cell. The Sample Injector introduces the cell suspension into the center of a fast-moving sheath stream inside the quartz Flow Cell. Because the sheath moves faster than the sample, viscous drag stretches the sample into a narrow core only a few micrometers across — hydrodynamic focusing — so cells line up single file. The Sheath System supplies this sheath at constant pressure from the Sheath Tank, passing it through a 0.2 µm Sheath Filter and a Debubbler so that no particulate or bubble registers as a false cell. A metering Sample Pump sets the sample volumetric rate, which is needed for absolute cell counting.

Illumination comes from the Laser Bench, typically the Blue Laser (488 nm) at 488 nm plus the Red Laser (640 nm) and Violet Laser (405 nm). Each beam passes through a Beam Shaper that forms an elliptical spot matched to the core, and is held at constant power by its Laser Driver and temperature-stabilized by a Laser TEC. The beams strike the core at spatially separated points so that signals from different lasers can be resolved in time.

Light leaving the interrogation point is gathered by the Optics Bench. A Collection Lens captures scatter and fluorescence, and a Dichroic Mirror Set of long-pass mirrors splits the light into successive bands, each cleaned up by a filter from the Bandpass Filter Set before reaching a detector. A Obscuration Bar blocks the direct beam from the forward-scatter path.

How it works

The Detector Array convert light into electrical signals. Forward-scattered light, measured by the Forward-Scatter Diode, scales with cell size; side scatter and fluorescence are measured by Photomultiplier Tube photomultipliers whose gain is set by the PMT HV Supply. As a cell crosses a beam, each detector produces a brief pulse. The Detector Preamplifier turns the photocurrent into a voltage, and the Acquisition Electronics digitize it: the ADC Bank samples every channel and the Pulse-Processing FPGA integrates each pulse to extract its height, area, and width. Height and area both relate to fluorescence intensity, while pulse width helps distinguish single cells from doublets stuck together.

Because fluorophores have overlapping emission spectra, signal in one detector often contains spillover from dyes meant for another. The software corrects this with a compensation matrix derived from single-stained controls, recovering the true contribution of each marker. The per-event data — a row of parameters for every cell — are streamed to the host, where analysts gate populations on scatter and fluorescence plots to isolate subsets such as a particular lymphocyte type.

The Sample Introduction feeds samples to the instrument, with a Sample Injection Probe aspirating from tubes and a Plate Loader indexing microplates for automated batches; a Sample Mixer resuspends settled cells first. Holding the lasers, flow cell, and collection optics in fixed mutual alignment is essential for reproducible signals, which is why the Optical Chassis uses a stiff Optical Baseplate and a Light Shroud to exclude ambient light from the sensitive detectors.