矩形微通道内水平温度梯度下向列相液晶非对称流动特性研究

Study on the Asymmetric Flow Characteristics of Nematic Liquid Crystal Under Horizontal Temperature Gradient in Rectangular Microchannel

微流控芯片在医药、化工等领域的广泛应用,对作为其核心部件的微阀提出了更高的要求。本文使用偏光显微镜结合粒子跟踪测速方法进行实验研究,观察了不同水平温度差下微通道内向列相液晶5CB的独特光学变化及非对称流动现象。研究结果表明,微通道内高低温区域速度差和分流比会随水平温差增加而增大。水平温差作用下微小槽道内向列相液晶温度及指向矢分布对其各向异性物性参数的影响是非对称流动产生的根本原因。最后,提出了一种以向列相液晶为化学试剂和微生物等分析检测样本的载体,并基于向列相液晶非对称流动特性来实现径流调节的新型温控微阀。

The wide application of microfluidic chips on areas of medicine and chemical engineering raises higher demand for the microvalve as the core component in microfluidic chips. In this paper,experiments are carried out by the combined methods of polarized optical microscopy(POM) and particle tracking velocimetry(PTV). The unique optical changes and asymmetric flow phenomena of nematic liquid crystal 5CB are observed. Results show that the split ratio and velocity difference between the hot and cold regions of the cross section of the microchannel increase with the increase of the horizontal temperature difference. The influence of the temperature and director fields of the nematic liquid crystal on the thermophysical parameters is the primary cause of the asymmetric flow.A novel kind of temperature controlled microvalve based on the asymmetric flow characteristics of the nematic liquid crystal to realize flow tuning is presented, with the nematic liquid crystal used as the carrier fluid of test samples such as chemical agents and microbes.