| The Volume scattering function (VSF) of particles is a key physical property. Conventional approaches of VSF studies mainly focuses on the indirect measurement with particle groups. Present methods which studied the VSF of single particle suffers from the inapplicability in conduct solutions and high dependency of the environmental factors, etc. Thus, it is significant to design a VSF measurement system which is stable, reliable, rapid and with low dependence of environmental features. A novel approach of VSF measurements was proposed based on a microfluidic chip of hydrodynamic single-particle-trapping, which solved the key problem of the VSF measurements of single particle By employing the hydrodynamic principle and the finite element method, the microfluidic chip with self-regulation has been designed and fabricated for the VSF measurement of single particle. An apparatus for receiving scattering light which utilized the spatial filter and PMT photon detector has also been designed and mounted based on the feature of single-particle-scattering. Combing the functional modules, the complete system has been successfully integrated and experimentally certificated for the VSF research of single particle.The properties of the flow field in a microfluidic channel was elaborated initially. Utilizing the flow resistance model, the geometric parameters and fluidic features has been calculated by Matlab coding. As a result, a microfluidic structure was proposed with a hydrodynamical feedback control by the trapped particle, high trapping efficiency and accuracy. A tool of finite element method was employed to simulate the 3D structure, in order to verify the reliability and optimize the local geometry. Based on these achievements,the highly transparent microfluidic chip which satisfies the requirements of the VSF measurement of the single particle was eventually fabricated.To detect the VSF of the trapped particle, an angle-resolved scattering receiving equipment of high dynamic range based on the spatial filter and PMT photon detector was designed through principle analysis, theoretic calculation and numerical simulation. Correspondingly, the field of view and the linearity in a large dynamic range of the light intensity was approved by experimental verification.Based on the achievement of modules of single-partilce-trapping and light scattering detection, the complete system of VSF measurement of single particle was developed. By eliminating the influence of imbibition of the organic solvent, fluctuation of the environment temperature and boundary layer of the laminar flow, the performance of the index-matching was improved. The experiment of VSF measurements of the trapped single particle has been implemented in a large angular range after the spatial alignment. By repeating the VSF measurements of 20.42?m particle between 2° and 162°, the coefficient of the variation was calculated as 20%-25% for the center value while the scattering light intensity varied at the range of 1×106. Given on this basis,20.42?m,23.75?m,31.10?m polystyrene microspheres were tested. The results showed a good agreement on the trend with the curves of Mie theory. The quantitative analysis between experimental data and theoretical curve was yielded by utilizing the curve fitting in the area between 20° and 55°. The parametric analysis indicated a good agreement between the theoretical and experimental data with the same size, while the maximum difference was 8.6%. The differences of the parameters among various particle groups were extremely significant, which showed a good accuracy and resolution of this VSF measurement system. In conclusion, this method was proved as a rapid, effective and potential candidate of VSF measurements of the single paticle, which have both the accuracy and the agreement with the theoretical result in the experimental test. |
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