2.1. Fabrication of microfluidic chip
The master molds were 3D-printed using Anycubic Photon LCD printer (China). Then, the molds were coated using trichloro (1H,1H,2H,2H-perfluorooctyl) silane (Sigma, USA, 448931). 2 ml of this coating agent was co-incubated with the molds in a vacuum desiccator overnight. Chips were composed of polydimethylsiloxane (PDMS; Dow Corning, USA, 761036). PDMS prepolymer solution was mixed with the curing agent at 10:1 ratio, poured onto molds or square dishes, and cured at 60 ℃ for 6 h. Cured PMDS parts were assembled (Fig. 2). The membrane for cell culture area was polyester membranes cut from transwell inserts with 0.4 μm pore size (Corning, USA, 3470).