Liquid Refractive Index Measurement System Based on Electrowetting Lens

Shi-Long Li,Yan-Ting Tian,Zhong-Quan Nie,Chao Liu

doi:10.3390/mi10080515

Shi-Long Li, Yan-Ting Tian + Show 2 more

Open Access

https://doi.org/10.3390/mi10080515

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Abstract

In this paper, a liquid refractive index (LRI) measurement system based on an electrowetting lens was proposed. The system is composed of a light source, a collimating lens, a liquid measurement chamber (LMC), an electrowetting lens and an image sensor, which is integrated into a cylindrical cavity. The refractive index of the LMC changes with the addition of the measured liquid, and the incident light cannot be focused on the image plane. By adjusting the driving voltage of the electrowetting lens, the curvature of the liquid-liquid interface changes to focus the incident light onto the image plane. The refractive index of the liquid could be measured according to the voltage value. The proposed LRI measurement system has no mechanical moving parts, and the imaging surface remains stationary, which can make the measurement simply and correctly. The experiments show that the refractive index measurement range of the system can be turned from ~1.3300 to ~1.4040, and the measurement accuracy is 10−4. The system can be used to measure the optical properties of liquids and has broad potential applications in chemical reagent detection and pharmaceutical testing.

Highlights

A refractive index is an important optical parameter of liquids
A novel liquid refractive index (LRI) measurement system based on an electrowetting lens was proposed
By adjusting the external driving voltage of the electrowetting lens, the spot will focus on the image plane, and the refractive index of the liquid can be calculated according to the applied voltage value

Summary

Introduction

A refractive index is an important optical parameter of liquids. With the refractive index, the optical properties, the purity, dispersion and diffusion coefficient of the fluids can be analyzed [1,2]. Conventional liquid refractive index (LRI) measurement systems can be classified into refractometers and interferometers, according to measurement methods [3,4,5,6]. By adjusting the external driving voltage of the electrowetting lens, the spot will focus on the image plane, and the refractive index of the liquid can be calculated according to the applied voltage value. Compared with the previous works, the liquid measurement chamber (LMC) in the proposed system is small in volume and sealed by a cavity Both a precious liquid and a volatile liquid can be measured. The proposed system has the advantages of small size, high integration, convenient carrying, simple operation, no restriction on liquid characteristics, and no mechanical moving parts

Structure and Mechanism of the System

Fabrication of the Proposed System

Discussion

Conclusions