A lateral flow test typically incorporates a sample pad that is intimately associated with a conjugate pad. This in turn touches a membrane onto which test and control reagents have been immobilised. An absorbent pad wicks fluid away from the membrane.

Dispensing Considerations for Lateral Flow

1. Test and control lines. These lines are typically an enzyme, antibody, antigen, or nucleic acid etc. These are immobilised on a membrane, usually made from nitrocellulose. The decision on whether to opt for contact versus non-contact will be down to membrane manufacturers' recommendations, and on the kinetics with which the immobilization occurs in the membrane matrix.
   
   To apply the lines BioDot offers contact (FrontLine™) and non-contact (BioJet™) technologies. Both FrontLine and BioJet are fully quantitative dispensers. The Frontline meters liquid using a high-resolution pump to drive a low volume syringe connected to a dragging tip. The BioJet drop-on-demand technology dispenses individual drops from 20 nL to 4 µL. The BioJet systems produce clearly defined, fine lines by overlapping individual drops at a tight pitch . The ability to control drop size, line volume, and energy of the drop give the researcher the control needed in the critical step of marrying reagents to materials.
   
   
2. Conjugate. Colloidal gold, monodisperse latex or paramagnetic particle conjugates are applied to a variety of pad materials using the BioDot AirJet dispenser. These conjugate solutions typically contain high concentrations of sugars and/or polymers for stabilization and release.
   
   BioDot offers the AirJet Quanti 3000 to evenly and quantitatively apply the conjugate to the pad in a surface coating, which vastly improves the efficiency of drying and conjugate release over immersion application methods. The dispensed pattern can be adjusted to provide more or less defined lines through control of the dispenser aperture size, air pressure, and dispensing rate. The use of quantitative AirJet dispensing is a critical component of the manufacturing process of quantitative or semi quantitative assays.
   
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