The lid is used directly to connect pressure source to all the channels. The plastic lid can easily be opened and resealed to the chip using two nuts and a rubber ring sealing. When the lid is attached, it encloses a common volume of air over all substance wells. By pressurizing this air through the lid, the flow is driven from each well and out into the recording chamber. Additionally the lid functions as a protective barrier, shielding both the user and the solutions.