| With the advancement of science and the development of human society,people’s eyes have gradually shifted from the macroscopic world to the tiny structures such as cells and proteins.In recent years,the exploration of the microscopic world has been a hot topic among scientists.Microfluidic technology provides an extremely important experimental platform for scientists to study the micro structure of substances due to its advantages of easy manipulation,small size and high throughput.In this platform,various characteristics of cells can be observed and studied,and the sorting of target cells can be realized through the judgment of cell characteristics.Most of the systems reported in the literature are self-built by various research groups in the laboratory.Their functions and performance have different advantages,and even their structure is being explored.Based on the current development trend in this field,this paper combines the latest research progress with technical means to build a modular application system with reasonable structure,good performance and convenient use.The integrated application system of microfluidic control can detect and distinguish microdroplets fluorescence,and separate target droplets,which meets the special requirements of this research direction.This system mainly consists of two parts:1.microfluidics systemIt is mainly divided into the following aspects: optical imaging and fluorescence spectrum acquisition unit;Fluorescence intensity detection unit;Control unit;Execution unit.2.Optics system and electronic systemIt is mainly divided into the following aspects: optical imaging and fluorescence spectrum acquisition unit;Fluorescence intensity detection unit;Control unit;Execution unit.In the optical system and fluorescence spectrum acquisition unit,a fluorescence signal detection light path,a multi-wavelength laser set,an inverted microscope,and a fluorescence spectrometer are set up,which enables the detection of fluorescence signal,bright field imaging and fluorescence spectrum of samples,and can be used for singlecell analysis.In the fluorescence intensity detection unit,the silicon avalanche photodiode(APD)with appropriate parameters is selected to detect the fluorescence signal,which meets the sensitivity requirements of signal detection.A current-voltage converting optical circuit(IV converting circuit)is designed by using the low noise operational amplifier OPA657,which converts the detected optical signal into an electrical signal recognized by the electronic system.A half-wave topological boost circuit is designed with TPS55340 switch power chip to meet the requirements of APD reverse voltage120V-160 V.Finally,the detection of weak fluorescence signal is achieved.In the execution unit,AD9834 direct digital synthesizer chip is used to design the circuit,and related programming is carried out to achieve the sinusoidal signal generation.The resulting sinusoidal signal is then amplified by a rear voltage amplifier to become a high-voltage alternating signal to drive the electrodes for liquid drop separation.The fluorescence intensity detection unit detects the fluorescence labeling signal of the micro-droplets and generates an intensity-related pulse signal which is collected by the STM32 micro-control system.The signal is identified by the fluorescence intensity discrimination program within the system.When the signal matching the screening target appears,the control pulse signal generator program generates the command and transmits it to the AD9834 direct digital synthesizer module in the execution unit.A high voltage alternating signal is generated and applied on the microfluidic sorting chip electrodes in the microfluidic control system to generate an electric field to separate the droplets.The work of the whole system is based on STM32 control unit.Because of its high performance,many interfaces have successfully linked each module to coordinate the whole system to achieve the detection and sorting of liquid droplets. |
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