Automated Fluidic Assembly of Microvessel-Like Structures Using a Multimicromanipulator System

There is currently a need for a high-throughput flexible assembly method to fabricate artificial microvessels from micro annular modules. In this paper, a novel bubble-assisted fluidic assembly method is presented and a multimicromanipulator system is set up to enable automation. To excite a microflow for assembly, microbubbles are generated by injecting air into the fluid via a glass pipette. The microflow is used to drive the annular module to move up along another glass pipette that passes through the center of the modules. A multimicromanipulator system is used to separately position the two pipettes and the annular modules through a visual servoing control. An adaptive Hough transform is used to detect the annular modules and optimized template matching is developed to obtain the three-dimensional positions of the two glass pipettes. Motion analysis of the annular module and the microbubble is performed to explain the theoretical principles of this method, and key parameters influencing the assembly are analyzed and identified. These parameters are further tested by experiments to improve the success rate and efficiency. Finally, microvessel-like structures with varying outer diameters are fabricated to demonstrate flexibility. Fully automated assembly of a 2.2 mm long microtube with 100% success rate is achieved and the average assembly time consumption per annular module is as low as 2.1 s.