Research and Design of Laser Drive System Based on Flow Cytometry
A flow cytometer is a cutting-edge technology that blends the technical aspects of lasers,electrophysics,optoelectronic measurement,computer technology,cell fluorescence chemistry,and monoclonal antibodies.Flow cytometers make use of laser light to stimulate the fluorescent dye inside cells to measure and analyze the latter's sizes,shapes,colors,and fluorescence.It offers a swift solution to multi-parameter quantitative analyses and sorting of fluid-state cells or bioparticles,which explains its extensive utility in life science research and clinical diagnostics.Seeing that the light power stability,wavelength stability,and photodetector noise rate of the flow cytometry significantly affect the experiment's accuracy,this study adopted a semiconductor laser as the driving light source for the flow cytometer to ensure a stable,low-noise laser light source.Semiconductor lasers'compact size,long lifespan,high brightness,high electro-optical conversion efficiency,and excellent directivity make them widely applicable for not only optical measurement and storage but also for military purposes,communication,and medical diagnostics.Despite the versatility,semiconductor lasers also feature an excitation method that involves current injection,which,when taken into account with its material characteristics,outputs light with features that are highly sensitive to the injected current and operating temperature.Research indicates that temperature rise can drastically reduce carrier concentration,significantly increase threshold current,decrease electro-optical conversion efficiency,and convert most electrical energy into wasteful heat,reducing the output light power to a minimal level.For instance,every milliampere of current change can cause an approximate 0.02 nm drift in the output light wavelength,and each degree Celsius temperature change can result in an approximate 0.1 nm drift in the output light wavelength.Additionally,prolonged operation in high-temperature environments will considerably diminish the lifespan of semiconductor lasers.In response to these current and temperature stability issues commonly associated with semiconductor lasers,a novel design of a drive system specifically tailored for flow cytometers is proposed.With an STM32 as the central control core,the drive system communicates with the flow cytometer's main computer via RS232 serial communication.The temperature control component employs a MAX8521 professional temperature control chip,coupled with an external hardware PI circuit and its internal H-bridge drive to swiftly and accurately control the thermoelectric cooler.This concerted configuration enables the system to maintain a constant working temperature for both the laser and photodiode.The driving component incorporates a deep negative feedback circuit for light power in conjunction with a PID algorithm,forming a dual closed-loop power control system.This arrangement ensures that the laser drive current closely aligns with the anticipated value,thereby providing precise and stable control of the laser's output power,minimizing laser output noise,and reducing potential wavelength drift.The experimental results demonstrate the system's slow temperature adjustment speed,with temperature fluctuations maintained within±0.016℃and a temperature control instability of just±0.055%.The laser's output characteristics remained relatively stable,exhibiting a±0.078%long-term light power output instability,a 0.109%photodetector noise rate,and a 637～638 nm stable output light wavelength.When applied to the flow cytometer for CV quality control experiments,the instrument resolution's full peak width variation coefficient was consistently less than or equal to 1.70%,surpassing the requirements set by the YY/T0588-2017 flow cytometer industry standard.In conclusion,the proposed system demonstrates exceptional precision in temperature control,maintains a stable and low-noise light power output,and minimizes light wavelength drift.It yields impressive CV test results through flow detection,fulfilling the requirements of flow cytometer detection,thus giving it substantial practical value.
Flow cytometrySemiconductor laserLaser power controlTemperature controlInstability
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