Study On Optical Fluidic Sensing Technology For Tracking Biomineralization Process

The microfluidic chip uses microchannels to realize the manipulation of fluids with small volume.It has the advantages of small size,fast response and high integration.This special characteristic has brought new progress to research and applications,meanwhile it also brings difficulties in process monitoring caused by low substance content.In response to the need for real-time,in-situ,and non-destructive monitoring of the material transformation process in the microfluidic chip,this thesis proposes to use optical-fluidic technology to perform real-time and non-destructive detection of the reaction process,and adopts a complex reaction system-biomineralization as the detection object.The four important stages during biomineralization: supersaturated state,amorphous nanoparticles,nucleation and growth are monitored and analyzed.The main research works includes:①For the monitoring of the nucleation process,a high throughput chip was designed and used to statistically analyze the nucleation rate of calcium carbonate crystals.This chip is designed to ensure large number of samples for study;its three sandwiched layer structure and water replenishment layer can effectively ensure the droplets with fixed volume and stable saturation.Finally,the nucleation rate of calcium carbonate was successfully measured using this device,and the nucleation rate when magnesium ions were used as a regulator was compared.②Aiming at the monitoring of ion concentration change during the supersaturation state,a semi-open chip and fluorescent detection probe are used to track the ion concentration change during the crystal growth process.A standard curve of fluorescence intensity vs the corresponding p H value was established by combining the designed semi-open microfluidic chip with a fluorescent probe.The p H of the solution at a certain time could be obtained based on the fluorescence intensity detected.Finally,the applicability of this method was verified by the mineralization process induced by Bacillus pasteurian,and the relationship between the p H change rate of the solution and the crystal growth rate under different bacterial concentrations was established.③For the monitoring of the transformation process from amorphous nanoparticles to stable crystal forms,synchrotron radiation X-rays are used to track the evolution of nanoparticles in the biomineralization process.A set of microfluidic devices suitable for synchrotron radiation detection was prepared,which solved the difficulties in reaction control,in-situ detection,complex microchannel preparation and large absorption.Finally,the device was used to monitor of the initial stage of calcium carbonate crystallization of nanoparticles and the change of amorphous calcium carbonate to the stable crystalline nanoparticles using in-situ small-angle scattering and wide-angle scattering.The additives’ effects on the stabilization of ACC were compared.The above mentioned optical fluid control technology based on the combination of optical imaging,fluorescence and synchrotron radiation X-rays and novel microfluidic chips meets the requirements for the detection of the material growth process on the chip in terms of biomineralization process monitoring.Compared with traditional detection methods,it has the advantages of real-time,in-situ and non-destructive.In fact,it is not only suitable for a mineralization process including supersaturation,nucleation,growth,and crystal transformation during synthesis,but also applicable to most materials synthesized in solution.Therefore,the method developed in this thesis is expected to be used for general applications in micro-reaction process monitoring.