How to Buy Flow Cytometers
27 October 2016


Flow cytometry is a powerful technique that simultaneously measures and analyzes multiple physical characteristics of single particles, usually cells, as they flow in a fluid stream through a beam of light. Flow cytometry is widely used for analyzing expression of cell surface and intracellular molecules, characterizing and defining different cell types in heterogeneous cell populations, assessing the purity of isolated subpopulations, and analyzing cell size and volume. These characteristics are determined using an optical-to-electronic coupling system that records how the cell or particle scatters incident laser light and emits fluorescence (Figure 2).

Over the past 30 years, flow cytometry has become an indispensable tool for many scientific researchers and clinicians. The evolving technology ensures its application in a number of fields, including cell biology, drug discovery, cancer research, neuroscience, stem cell research, pathology, immunology, hematology, plant biology, food science and marine biology.

Flow Cytometry Technology

flow cytometer is made up of three main systems (Figure 2). The fluidics system transports particles in a sample stream to the interrogation point and takes away the waste (Figure 1). The optics system consists of lasers to illuminate the particles in the sample stream and optical filters to direct the resulting light signals to the appropriate detectors. The electronics system converts the light signals from the detectors, into electronic signals that can be processed by the computer. For some instruments equipped with a sorting feature, the electronics system is also capable of initiating sorting decisions to charge and deflect particles.

The Fluidics System
The  fluidics system within the flow cytometer transports particles in a fluid stream to the laser beam for interrogation (Figure 1). When a sample in solution is injected into a flow cytometer, the particles are randomly distributed in a three-dimensional space. For accurate data collection, it is important that the particles or cells are passed through the laser beam one at a time. Most flow cytometers accomplish this by injecting the sample stream into a stream of faster flowing sheath fluid within the flow chamber. The flow of the sheath fluid accelerates the particles and restricts them to the center of the sample core, so that a single stream of particles is created. This process is known as hydrodynamic focusing (Figure 1A). A newer flow cytometer uses a variation of the traditional hydrodynamic focusing called acoustic-assisted hydrodynamic focusing. This technology uses ultrasonic radiation pressure (>2 MHz) to transport particles into the center of the sample stream. This pre-focused stream is then injected into the sheath stream, which supplies an additional hydrodynamic pressure to the sample. The combination of these two forces – termed acoustic-assisted hydrodynamic focusing – results in a narrow core stream and uniform laser illumination, regardless of the sample input rate (Figure 1B). In traditional cytometers that rely solely on hydrodynamic focusing, the sample core widens to accommodate the increases in flow rate, which results in less uniform laser light illumination (Fig