Application Of Microfluidic Chips To Holographic Microscopy For Micro Particles And Reversible Ammonia Detection

The microfluidic-chip-based analysis has became a core field of the analytical science for its rapidity,integration,accuracy,low sample consumption and precise controlling.Digital holography for particles and apectra analysis for ammonia detection has attracted great attention for the perfect optic properties of the microfluidic chips made of PDMS.The microfluidic-chip-based analysis,however,does not mean the simple minimization of the system.The lack of knowledge in the micro field leads to various flaws in digital holography for particles and apectra analysis for ammonia detection.Little work has been done do study the multi-distrubition micro particle field in digital holography.The issues in indicator selection,the design of the chips and the selectivity still exist in apectra analysis for ammonia detection.In order to settle these issues,this paper conducts larges amounts of experiments by using microfluidic chips as the analytical platform.On one hand,we do a lot of research to study the multi-distrubition micro particle field in digital holographic microscopy and test real samples to support our research.On the other hand,the reversible ammonia detection in liquid phase is realized by immobilization of ZnTPP in the spin-coated PDMS thin film.We also investigate the time response,impact factors and the influence of interferences of the method.Aiming to promote poor selectivity,an improved design of the coupled microfluidic chip is presented to realize the highly selective reversible ammonia detection in complex liquid environment,followed by research of impact factors and real sample tests.The detailed contens are as follows:Firstly,under the far field condition of of plane wave formed by Gauss beam,we set up the digital holographic microscopy system and study the micro particles in the PDMS microfluidic chip with wavelet reconstruction.Having determined the equivalent pix and the magnification,the experiment for the single-distribution standard particle field is done to confirm the accuracy of the digital holographic microscopy in flowing state.By analyzing the reconstruction results for solution containing various ratio of micro particles with different diameters,the reasonabililty to measure multi-distrubition micro particle field is demonstrated.Then the complex sample obtaining after a WESP is analyzed.Large numbers of hologram is taken and reconstructed,followed by the comparison between the results from the digital holographic microscopy and the standard method.Secondly,the reversible ammonia detection is realized by the designed 4-layer microfluidic chip where the indicator?ZnTPP?material is immobilized in the spin-coated PDMS immobilization film.By analysis of the continuous spectrum,the response wave range is revealed.The relationship between the response and ammonia concentration is investigated under specific wavelength.Then the reversibility of the chip,the stability of the indicating performance and the time responses for the indicating stage and recovering stage are studied.The common interferences are tested and analyzed last.Thirdly,the impact factors of the reversible ammonia detection chip are investigated.Through the indicating results obtained by cation exchange resin microbeads with various diameters,the smaller ones are proved the optimal selection.The spin-coating speed of the PDMS immobilization film during the fabrication process is studied in terms of indicating performance,time response,reversibility and stability.With the degeneration of ZnTPP being the sign,the service life of the microfluidic ship is pointed out by large numbers of cycles.In addition,the detection limit is demonstrated.Fourthly,a coupled microfluidic chip composed of the reaction chip,the gas-diffution chip and the detection chip is designed and fabricated to settle the issue of low selectivity of ZnTPP and realize the highly selective ammonia?ammonium?detection in complex liquid phase.The indicating performance is investigated by the experiments for various contrations of NH₄⁺.The common interferences HCO₃^-and OH^-are tested,confirming that the coupled microfluidic chip can eliminate the interferences and promote the selectivity of ZnTPP.Further experiments are conducted to reveal other properties of the coupled chip.Through the test of real complex samples and the comparison with the standard method,the coupled microfluidic chip is confirmed to be able realize highly selective ammonia?ammonium?detection in complex liquid phase.Finally,the key parameters of the coupled microfluidic chip is studied and optimized.The key parameters includes the length of the reaction channel in the reaction chip,the thickness of the PDMS gas-diffusion membrane,the way of gas-diffusion,the flow rate in the reaction chip and the gas-diffusion chip,the amount of the indicating material in the detection chip.Through the relationship between the indicating performance and these tests,the oprimal parameters for the coupled microfluidic chip are determined.