All-Optical Microfluidic Technology Enabled by Photodeformable Linear Liquid Crystal Polymers

Abstract

The microfluidic biochemical/immunoassay systems typically consist of microfluidic chips, fluid driving devices, and detection components. The core of the system is the microfluidic chips based on microfluidic technology, which are typically constructed with nonresponsive materials such as silicon, glass, and rigid plastics, thus requiring complex external air/liquid pumps to manipulate the samples. The external equipment renders the microfluidic systems cumbersome and increases the risk of biosample contamination. The all-optical microfluidic chip (AOMC) integrates all necessary microfluidic units and uses light to manipulate microfluids, which has the potential to completely solve the major problems of miniaturization and integration in microfluidic systems. The photocontrolled manipulation in AOMCs facilitates contactless interaction with liquids, eliminating the need for physical interconnects such as complex external electric, hydraulic, or pneumatic devices and replacing the traditional microfluidic components such as pumps, mixers, and separators, which offers AOMCs improved flexibility, robustness, and portability. However, impeded by photocontrolled principles and appropriate materials, AOMCs and photocontrolled biochemical/immunoassay analyzers have never been created.

This Account highlights our efforts toward the new conception of all-optical microfluidic technology enabled by photodeformable linear liquid crystal polymers (LLCPs). We propose a novel mechanism to drive microfluids by the photoinduced Laplace pressure (asymmetric capillary force) and construct the first photodeformable 3D channel with newly designed photodeformable LLCPs possessing superior processability and photodeformability. The attenuated light is utilized to precisely control the axial asymmetric deformation of the 3D channels, which generates Laplace pressure, driving the fluids spontaneously toward the narrow end of the microtubes. Consequently, the photodeformable 3D channel integrates dual functions of the fluid channel and the pump, which is suitable for the construction of AOMCs, the core components of all-optical microfluidic technology, and lays the foundation for the miniaturization of microfluidic systems. By replacing the conventional chip materials with the photodeformable LLCPs, we construct the AOMC for the first time and achieve noncontact, accurate, and efficient manipulation of microfluids using a single light source, which plays an important role in solving the core conundrum of the cumbersome external equipment in the microfluidic chip systems. The AOMCs provide a robust platform for biochemical analysis such as protein detection and the catalytic oxidation reaction with minimal sample consumption, reduced reaction times, and enhanced portability, thus demonstrating the potential in in vitro detection with the ultratrace sample. Finally, we discuss the future challenges and opportunities inherent to all-optical microfluidic technology.