Lateral-flow assay device having flow constrictions
A lateral-flow assay device includes a substrate having a sample addition zone and a wash addition zone downstream thereof along a fluid flow path through which a sample flows. The fluid flow path is configured to receive a wash fluid in the wash addition zone. A hydrophilic surface is arranged in the wash addition zone. Flow constriction(s) are spaced apart from the fluid flow path and arranged to define, with the hydrophilic surface, a reservoir configured to retain the wash fluid by formation of a meniscus between the hydrophilic surface and the flow constriction(s). The fluid flow path draws the wash fluid from the reservoir by capillary pressure. Apparatus for analyzing a fluidic sample and methods of displacing a fluidic sample in a fluid flow path of an assay device are also described.
1. A method of displacing a fluidic sample in a fluid flow path of an assay device, the method comprising:
dispensing the fluidic sample from a sample supply onto a sample addition zone of the assay device, wherein the dispensed fluidic sample travels along the fluid flow path of the assay device; and
dispensing a wash fluid from a wash-fluid supply onto a wash addition zone of the assay device downstream of the sample addition zone along the fluid flow path so that a meniscus is formed in the dispensed wash fluid by at least one flow constriction of the assay device, wherein the at least one flow constriction is created by substantially circular grooves disposed substantially around the wash addition zone, and wherein the fluid-flow path draws dispensed wash fluid out of a reservoir defined at least partly by the meniscus and the drawn wash fluid displaces at least some of the fluidic sample in the fluid-flow path.
2. The method according to claim 1 , further comprising, after said dispensing the wash fluid, determining the presence of a detectable signal corresponding to a characteristic of the dispensed fluid sample.
3. The method of claim 1 , which includes determining the presence of the detectable signal at a detection zone of the assay device downstream of the wash addition zone.
4. The method of claim 3 , wherein determining the presence of the detectable signal includes using a detection material included within the detection zone, the detection material responsive to an analyte of the fluidic sample.
5. The method according to claim 1 , wherein the fluidic sample is configured to flow along the fluid flow path through the wash addition zone via capillary forces.
6. The method according to claim 5 , wherein the fluidic sample is configured to flow straight through the wash addition zone.
7. The method according to claim 5 , wherein the fluidic sample is configured to curve through the wash addition zone.
8. The method according to claim 1 , wherein dispensing the wash fluid includes dispensing the wash fluid onto a hydrophilic surface of the wash addition zone.
9. The method according to claim 1 , wherein the wash fluid is configured to spread laterally across the wash addition zone until contacting the at least one flow constriction.
10. The method according to claim 1 , which includes incubating the assay device prior to determining a presence of a detectable signal corresponding to a characteristic of the dispensed fluid sample.