Abstract
Measurements on refractive index and its distribution of microfluidics are widely applied in the field of biological detection, chemical analysis, material researches, medical diagnostics, and lab on a chip. Since the volume of the microfluidics is ultra-small, such as nanoliters or even picoliters, measuring the refractive index of microfluidics is challenging. We here presents an effective method to measure the refractive index and its two-dimensional distribution of picoliter microfluidics by the SWLI (scanning white light interference) microscopy technology. This method has the advantages of simplicity, low cost, non-contact, wide measurement range and high precision. We conduct the experiment to measure the refractive index of 2.4 picoliters liquid. The resolution is 10−4RIU (refractive index unit), and the relative error is 10−4 compared with the Abbe refractometer. We obtained the relationship between refractive index and concentration of glucose solution. In addition, we can measure the 2D (two-dimensional) distribution of RI (refractive index) of liquids. We can observe the liquid interface between deionized water and liquid paraffin clearly. Besides, we can observe the process of solute dissolution in the liquid and the change of refractive index.
Highlights
Studies of nanoliters or picoliters liquids are crucial for microfluidics technology [1], [2]
To adjust the limitations of the above methods, here we propose a method to measure the RI and its 2D distribution of ultra-small volume of liquids by scanning white light interference imaging technology
In summary, a simple measurement method of RI of microfluidics based on scanning white light interference is applied to achieve high precision measurement of picoliter liquid
Summary
Studies of nanoliters or picoliters liquids are crucial for microfluidics technology [1], [2]. The cost is high and the equipment is complicated They can only measure a small volume of liquid and it is extremely time-consuming to measure the distribution of RI point by point. To adjust the limitations of the above methods, here we propose a method to measure the RI and its 2D distribution of ultra-small volume of liquids by scanning white light interference imaging technology. The proposed method does not need physical contact with the sample It has high precision and wide measurement range. This method is expected to be applied in biological detection, chemical analysis and chip analysis fields. Such as the detection of cell growth status, chemical reaction detection, fluids mixing process, and microfluidics properties
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