Research On Quantitative Detection Of Microfluidics Based On Scanning White Light Interference Technology

In recent years,people have developed miniaturized and highly integrated microfluidics chips.Due to their small size(generally from nanoliters to picoliters),the consumption of samples in a single experiment is small,the heat and mass transfer speed is faster,and various reactions are easy to control.They have become important research objects in many fields such as cell biology,medical diagnosis,and optical communication.The core part of the microfluidics chips are the microfluidics,so the quantitative detection of the microfluidics is of great significance.However,due to the small size of the microfluidics and the semi-closed microchannel,the detection of the microfluidics needs to pass through the chip package shell,which brings challenges to the quantitative detection of the microfluidics.Current methods are difficult to achieve high-precision detection on ultra-small volumes,and most of them require fluorescent labels or need to contact samples,which will cause contamination of microfluidics samples.In order to solve the above problems,this paper proposes a quantitative detection method of microfluidics based on scanning white light interference technology,which is a non-contact,no fluorescent label,high precision and rapid detection method.The main research contents are as follows:First,an improved scanning white light interference detection system is built.We adjust the optical path difference to meet the coherent conditions by adding a compensation plate.Comparing different algorithms of white light signal peak extraction,it is concluded that the Morlet wavelet transform method has strong anti-interference ability and high calculation accuracy.On this basis,a refractive index distribution measurement algorithm is proposed.Secondly,the surface topography of the microchannel structure is reconstructed,and on this basis,the refractive index measurement of the microfluidics is realized.The detection volume is2.4 picoliters,and the detection resolution reaches the pixel level.Compared with the measurement results of the classic Abbe refractometer,the relative error is about 0.03%,and the refractive index resolution is 10^-4 RIU.At the same time,the measurement of the refractive index distribution of the microfluidics is also realized,the liquid separation interface of the two microfluidics is detected,and the stepped refractive index distribution detection is realized.Then,the change of refractive index of the microfluidics is measured,including the change of refractive index with concentration.Taking glucose solution and urea solution as examples,the linear relationship between concentration and refractive index is verified,and the refractive index and concentration of two solutions at room temperature are obtained.The empirical relationship of illustrates the feasibility of the system to measure the concentration of microfluidics.We measure the change of refractive index distribution with time in the process of glucose dissolution.We verify the feasibility of the system to measure the dynamic distribution of refractive index.We measure the refractive index changes of the products after the denaturation of bovine serum albumin caused by different concentrations of urea.The results match the changes in the structure of the protein after denaturation detected by the fluorescence spectroscopy,indicating that this method has broad application prospects in biology.Finally,according to the relationship between temperature and refractive index,we propose a method to measure the temperature field of microfluidics based on scanning white light interference technology.We use optical fiber as a heat source,and measure the temperature field of microfluidics.The results show that the peak temperature of the microfluidics is about 83?,81?,and 121?for the flat end face,the bevel end face,and the tapered fiber.The peak temperature is approximately proportional to the optical power.The finite element method is used to simulate the electric field,steady-state heat transfer field,and temperature distribution near the end face of the optical fiber.The results obtained are in good agreement with the measurement results.