Micromanipulation for Coiling Microfluidic Spun Alginate Microfibers by Magnetically Guided System

Alginate hydrogel microfibers are a promising cell-laden module for three-dimensional (3-D) assembly to build cellular structures. However, it is still a challenge to manipulate them for microassembly. In this letter, we report a novel magnetic control method to handle this challenge. To enhance the controllability, we mix magnetic nanoparticles (MNPs) into alginate solution, and then spin magnetic alginate microfibers (MAMs) by a microfluidic device. To achieve precise magnetic control, we establish a magnetically guided system composed of a magnetic tweezer with a needle tip and a glass micropipette mounted on two manipulation robots, respectively. Moreover, a series of experiments have been designed to obtain the optimized solenoid current and tip structure of magnetic tweezer. Furthermore, a manipulation of coiling MAM around a micropillar at the microscale can be experimentally demonstrated. Based on such manipulation, a microassembly of MAM can be finally achieved to form a tube-shaped microstructure for 3-D cell culture.