Hi! I want to design a microfluidic device. I have an assembled model and need to open channels. I tried swept cut but it gave an error. What else I can use to have channels in an assembled solid?

I have an assembled microfluidic device design. I need it as assembled instead of one part. I tried to open channels inside the model and used the swept cut but it gave an error. Is there any other method to have the channels. I attached one channel example to make it clear. For the assembled model channels must be in the interconnected area.

SolidworksAssemblies