In-Situ Bonding of Multi-Layer Microfluidic Devices Assisted by an Automated Alignment System

Three-dimensional multi-layer microfluidic device (MMD) fabricated by polydimethylsiloxane (PDMS) is a solution for on-chip high-complexity serial or parallel processes. In this letter, we propose and set up an automated 8-DOF alignment system assisted by computer vision, which is capable of automatic leveling, aligning, and in-situ bonding of multiple PDMS layers. A microscope is motorized by a Z stage with a grating ruler to optically focus the marks and record the Z positions. A 3-PRS mechanism with flexible hinges is proposed to achieve the leveling of the top layer. An XYZR platform is utilized for in-plane alignment of the top layer and moving the top layer down to bond with the bottom layer. The Z positions of marks, translational and rotational offsets obtained by image processing are used for the automated leveling and aligning of the PDMS layers. Experimental results showed that translational and rotational alignment errors are less than 5 μm and 0.1°, respectively. The whole bonding procedure, including the plasma treatment, took the time shorter than 3 mins. Finally, a fabricated 3-layer microfluidic device with a deformable microchannel is applied to the cell squeezing and proved that the proposed alignment system has great potential in developing the functional MMDs.