Organ-on-a-Chip is an in vitro model for growing cells in microfluidic channels. The problem I am currently encountering is that Calu-3 cells cannot fill up my chip flow channel. I have tried cell concentrations of 2*10^6, 3*10^6, and 5*10^6 cells/mL, and they all failed. I cannot make the chip continue to grow after being converted to the ALI(Air Liquid Interface) state. I would want to ask, has anyone encountered similar problems? Is it a problem with the ECM coating? Or is the cell density not high enough?Welcome to discuss or give suggestions, thanks.