The Construction Of Multiple Point Of Care Testing Microfluidic Chip Based On Quantum Dot Microgel And Its Application In Heavy Mental Ions Detection

Heavy metals are toxic,and their pollution has shown severe threats to human health and ecosystem.Heavy metal ions such as Cu²⁺,Fe³⁺,CO²⁺,Pb²⁺are harmful to human body and environment even with very low concentrations.Meanwhile,heavy metal ions can be accumulated in animals and plants by food chains to advanced organisms.For human body,heavy metal ions can store in the organs and lead to various diseases.At present,some methods have been developed for heavy metal ions detection,such as atomic absorption spectrometry,emission spectrometry,ion selective electrode and traditional indicator.These methods usually require large-scale instruments and complex pre-processes,high energy consumption,high cost,and poor selectivity.Therefore,it is of significance to design and develop an equipment for on-site rapid and Point-of-care Testing of heavy metal ions.Microfluidic system,also known as Micro Total Analysis System（μ-TAS）or Lab of Chip（LOC）,has attracted intensive attention in various field.Microfluidic system has advantages over traditional technology in fast,high throughput,miniaturization,automation and parallel processing.In the sensing system,the detection issues will arise when sensing systems are miniaturized.The reduced analysis volumes mean a reduction in detection volumes,decreasing the number of analytes available for detection and making it more difficult to detect them.Thus,the two main factors that affect the choice of the detection method for microfluidic devices are sensitivity and scalability to smaller dimensions.Therefore,we consider coupling and integrating the corresponding optical sensor into the microfluidic device to meet the requirement of sensitive portable systems construction.Quantum dots microgels are assembled into compact detectors to develop a portable instrumentation based on microfluidic devices.In this study,a microfluidic chip based on quantum dots microgels was designed.First,in order to explore the internal structure of the chip,channels and microcolumns of different sizes are designed and CFD-ACE software is used to simulate the fluid flow,it provides the basis for us to select geometric structure and conditions of constructing quantum dots gel.With the microcolumn radius of 100μm,the microcolumn spacing of 550μm and the flow rate of 5 m L/min,the QDs microgel can be successfully manufactured by patterning the precursor in micropillars,and then UV curing.Afterwards,three kinds of quantum dots were synthesized for specific detection.Their physical and chemical characteristics were characterized by UV-vis and fluorescence for specificity,concentration response and detection limit quantization.The Pb²⁺detection quantum dots are GSH-Capped Cd Te quantum dots with absorption band at 350 nm and detection limit of 13.14 n M.The Cu²⁺detection quantum dots are MPA-Capped Cd Te/Zn S quantum dots with absorption band at425 nm and detection limit of 15.2 n M.The Co²⁺detection quantum dots are S quantum dots with absorption band at 325 nm and detection limit of 81.88 n M.The Fe³⁺detection quantum dots are from laboratory with absorption band at 375 nm and detection limit of 93.30 n M.Based on microfluidic technology,a microfluidic chip with microgel arrays for simultaneously detection of multiple heavy metal ions was designed,which consists of a sample perfusion area in the center（pipe width 200μm）,and four detection chambers（width8000μm,length 20000μm）with micro-pillars arrays（radius 100μm,width 550μm）in it,all of them height are 100μm.Interference experiments and the surface morphology of each quantum dot microgel were studied,the results shows that the gel composition has almost no effect on the performance of quantum dots and the microgel has enough space after losing water to absorb the sample solution and react with the analyte.Furthermore,the chip is applied in the detection of actual sample,such as lake water,soil and vegetables,the detection areas are photographed and the change in fluorescence intensity is recorded.After the quantum dot microgel is quenched,the brightness decreases to less than 40%of the original,and the quenching is visible to naked eyes.The results indicate that this method realizes the detection of multiple heavy ions detection rapidly and availably.