The comparison of two main materials in microfluidics, namely glass and polymers, shows their specific strengths and weaknesses. You might want to use glass if your set-up requires elevated temperatures, much above 100°C, which is usually not the case in life sciences, and/or if you need to use specific organic solvents. If you want to store bio-reagents on-chip, you need complex fluidics or hybrid components like membranes, or valves should be part of your device, etc., you will want to choose polymers, since interfaces, reservoirs, and different structural depths do not impact the price of the device in polymers, but are partially impossible to be implemented in a glass device or massively increase the cost. Possessing different characteristics and financial benefits, you will always use polymers when you don’t require glass, since they are the overall cheaper devices.