Photocontrolled Liquid Transportation in Microtubes by Manipulating Mesogen Orientations in Liquid Crystal Polymers

Abstract

Tubular microactuators (TMAs) fabricated by photodeformable liquid crystal polymers (LCPs) pave a significant way for smart microfluidic applications with contactless, spatial, and precise manipulation of liquids. To realize liquid transportation in these TMAs, LCPs should have excellent photodeformation property and suitable mechanical properties. Herein, linear liquid crystal polymers (LLCPs) with different mesogen orientations are used to prepare TMAs to study their liquid transportation behaviors. The mesogen orientation in each LLCP is formed spontaneously and varies with the spacer length, leading to different deformations of LLCP films. It is found that only LLCPs with mesogens oriented out-of-plane realize self-support of the TMAs, whereas the TMAs with mesogens oriented in-plane are so weak that they collapse in the radial direction, indicating the importance of mesogen orientation in fabricating three-dimensional structures. Upon attenuated 470?nm light irradiation, the TMAs deform to an asymmetric conical structure, leading to the motion of liquid slug toward the narrow side. The liquid motion is accelerated in the TMA with longer spacer, showing the control of liquid speed by the mesogen orientation. These photocontrolled TMAs are expected to be applied in biological applications, such as whole blood analysis and flow cytometry, for precise liquid manipulation.