Should I use contact or non-contact dispensing to print my control and test lines?
The test and control lines can be striped onto the nitrocellulose membranes using either contact or non-contact dispensing. While the contact dispenser represents a cheaper alternative that necessitates little maintenance, it is designed for quantitative tests, giving higher variance in dispense volumes than non-contact. Further, many membrane manufacturers do not recommend touching their membrane surfaces fearing damage to the surface, particularly on more delicate structures of open pore membranes.
Frontline dispensers (BioDot, Irvine CA) are an example of contact dispensing. A meniscus of fluid is dragged onto the nitrocellulose at a speed sufficiently slow to be absorbed into the membrane. By contrast the BioJet dispenser ejects drops of defined volume with high reproducibility and improved coefficient of variability on drop volume versus non-contact methods. With the appropriate center-to-center drop pitch and drop volume, the drops overlap to form a continuous, fine line. Further, the risk of damaging the membrane is removed.
See the following link to BioDot's YouTube channel for videos of BioJet and Frontline dispensing.