FIELD OF THE DISCLOSURE

The present disclosure relates to a heater design for a microfluidic test card, and more specifically to a screen-printed heater design which can be used to perform a polymerase chain reaction (“PCR”) within the test card.

BACKGROUND

Point-of-care (“POC”) in vitro diagnostics tests (“IVDT”) have traditionally had two major categories, nucleic acid amplification tests (“NAAT”) or immunoassay-based tests. The former directly detects a pathogen's DNA or RNA, while the latter detects antibodies or antigens generated by a patient's (human or animal) immune system response to the pathogen.

Current POC diagnostic immunoassays lack the high sensitivity and specificity of nucleic acid amplification methods. This becomes more pronounced during the initial stages of infection, often within 168 hours. Taking the case of Dengue virus in whole blood, immunoglobulin M (“IgM”) and immunoglobulin G (“IgG”) remain undetectable in the majority of patients until 5 and 10 days post-infection, respectively, whereas nucleic acid can be found as early as 0 to 7 days. Moreover, many immunoassay tests are unable to detect infectious agents until 3 months after the initial onset of the infection. This delay is due to the time it takes for the body's immune system to respond to an infection.

POC diagnostic assays developed utilizing NAATs have very high sensitivities and specificities, matching those of currently accepted laboratory tests. The primary mechanism of NAAT based systems is to directly detect an infectious agent's nucleic acid, lending to the test's ability to detect diseases within the first few days of the onset of infection. In addition, by careful primer design, NAATs also have the ability to have very high specificity and sensitivity compared to immunoassay based testing. The largest drawback of NAATs compared to immunoassay-based tests is the complicated equipment and/or processes required to prepare a sample for testing.

Some known POC immunoassay testing systems analyze a patient sample during early stages of infection by causing a polymerase chain reaction (“PCR”) within a test card. To cause the PCR, the patient sample has to be mixed with one or more reagents, such as a primer (e.g., oligonucleotides), a DNA polymerase, and/or a modified DNA polymerase. In addition, to cause the PCR, the reagent-patient sample mixture has to be heated on the test card. One issue that exists with test card screen-printed heaters is thermal uniformity, where a large temperature gradient results from a non-uniform current density. For example, a temperature gradient can be as large as 20 degrees over a 6 mm square area, which may cause major issues for PCR's, which require precise temperature control.

SUMMARY OF THE DISCLOSURE

Described herein is a screen-printed heater that is capable of uniformly raising a temperature of a fluid sample within a microchannel to cause a PCR. In a general example embodiment, which may be used in combination with any other embodiment disclosed herein, a test card for analyzing a fluid sample includes at least one substrate layer including a microchannel extending through at least a portion of one of the substrate layers, and a printed substrate layer that is bonded to or printed on one substrate layer of the at least one substrate layer. The printed substrate layer includes a heater printed on the printed substrate layer so as to align with at least a portion of the microchannel. The heater includes two electrodes aligned on opposite sides of the microchannel, and a plurality of heater bars electrically connecting the two electrodes. The plurality of heater bars includes a central heater bar disposed between outer heater bars. The central heater bar may be thinner than the outer heater bars in a direction approximately parallel to the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the at least one substrate layer includes a plurality of bonded layers.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the electrodes are printed onto the printed substrate layer with a silver ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars is printed onto the printed substrate layer with a carbon ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars includes the central heater bar, a pair of first outer heater bars, and a pair of second outer heater bars, the central heater bar is disposed between the first outer heater bars, the first outer heater bars are disposed between the second outer heater bars, the central heater bar is thinner than the first outer heater bars in the direction approximately parallel to the microchannel, and the first outer heater bars are thinner than the second outer heater bars in the direction approximately parallel to the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at respective portions aligned with the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars each includes a central diamond shape and two protruding ends, and the protruding ends overlap with the two electrodes to place the two electrodes in electrical communication with each other.

In a general embodiment, which may be used in combination with any other embodiment disclosed herein, a test card for analyzing a fluid sample includes at least one substrate layer including a microchannel extending through at least a portion of one of the substrate layers, and a printed substrate layer that is bonded to or printed on one substrate layer of the at least one substrate layer. The printed substrate layer includes a heater printed on the printed substrate layer so as to align with at least a portion of the microchannel. The heater includes two electrodes aligned on opposite sides of the microchannel, and a plurality of heater bars electrically connecting the two electrodes. The plurality of heater bars include a central heater bar disposed between outer heater bars, where the central heater bar has a higher resistance than the outer heater bars.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the at least one substrate layers includes a plurality of bonded layers.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the electrodes are printed onto the printed substrate layer with a silver ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars is printed onto the printed substrate layer with a carbon ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars includes the central heater bar, a pair of first outer heater bars, and a pair of second outer heater bars, the central heater bar is disposed between the first outer heater bars, the first outer heater bars are disposed between the second outer heater bars, the central heater bar is thinner than the first outer heater bars in a direction approximately parallel to the microchannel, and the first outer heater bars are thinner than the second outer heater bars in the direction approximately parallel to the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at respective portions aligned with the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars each includes a central diamond shape and two protruding ends, and the protruding ends overlap with the two electrodes to place the two electrodes in electrical communication with each other.

In another general embodiment, which may be used in combination with any other embodiment disclosed herein, a heater for a substrate includes two electrodes spaced apart from each other in a first direction, and a plurality of heater bars connecting the two electrodes, the plurality of heater bars including a central heater bar disposed between outer heater bars, the central heater bar being thinner than the outer heater bars in a second direction approximately perpendicular to the first direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the outer heater bars are progressively thicker in the second direction as the distance from the central heater bar increases in the second direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars are each shaped to be thickest at a central point between the two electrodes in the first direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the electrodes are printed onto the substrate with a silver ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars is printed onto the substrate with a carbon ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars includes the central heater bar, a pair of first outer heater bars, and a pair of second outer heater bars, the central heater bar is disposed between the pair of first outer heater bars, the first outer heater bars are disposed between the second outer heater bars, the central heater bar is thinner than the first outer heater bars in the second direction, and the first outer heater bars are thinner than the second outer heater bars in the first direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the heater is printed onto the substrate with conductive ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, a heater for a substrate includes two electrodes spaced apart from each other in a first direction, and a plurality of heater bars connecting the two electrodes, the plurality of heater bars including a central heater bar disposed between outer heater bars, the central heater bar having a higher resistance than the outer heater bars.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the outer heater bars have progressively less resistance as the distance from the central heater bar increases in a second direction approximately perpendicular to the first direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars are each shaped to be thickest at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the electrodes are printed onto the substrate with a silver ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars is printed onto the substrate with a carbon ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the plurality of heater bars includes the central heater bar, a pair of first outer heater bars, and a pair of second outer heater bars, the central heater bar is disposed between the first outer heater bars, the first outer heater bars are disposed between the second outer heater bars, the central heater bar is thinner than the first outer heater bars in a second direction approximately perpendicular to the first direction, and the first outer heater bars are thinner than the second outer heater bars in the second direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the central heater bar is thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the heater is printed onto the substrate with conductive ink.

In another general embodiment, which may be used in combination with any other embodiment disclosed herein, a method of providing a heater on a substrate includes printing two electrodes spaced apart from each other in a first direction, and printing a plurality of heater bars connecting the two electrodes, the plurality of heater bars including a central heater bar disposed between outer heater bars, the central heater bar being thinner than the outer heater bars in a second direction approximately perpendicular to the first direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the outer heater bars to be progressively thicker as the distance from the central heater bar increases in the second direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars to each be shaped to be thickest in the first direction at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the electrodes onto the substrate with a silver ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars onto the substrate with a carbon ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars so as to include the central heater bar, a pair of first outer heater bars, and a pair of second outer heater bars, the central heater bar is disposed between the first outer heater bars, the first outer heater bars are disposed between the second outer heater bars, the central heater bar is thinner than the first outer heater bars in the second direction, and the first outer heater bars are thinner than the second outer heater bars in the second direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the central heater bar to be thinner than the outer heater bars at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the central heater bar to be thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the two electrodes and/or the plurality of heater bars onto the substrate with conductive ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the two electrodes so as to be aligned on opposite sides of a microchannel extending through at least a portion of the substrate.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars so as to overlap a microchannel extending through at least a portion of the substrate.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars so as to overlap the microchannel in a direction approximately perpendicular to the direction of the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars before printing the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the two electrodes to at least partially overlap the plurality of heater bars.

In another general embodiment, which may be used in combination with any other embodiment disclosed herein, a method of providing a heater on a substrate includes printing two electrodes spaced apart from each other in a first direction, and printing a plurality of heater bars connecting the two electrodes, the plurality of heater bars including a central heater bar disposed between outer heater bars, the central heater bar having a higher resistance than the outer heater bars.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the outer heater bars to have progressively less resistance as the distance from the central heater bar increases in a second direction substantially perpendicular to the first direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars to each be shaped to be thickest at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the electrodes onto the substrate with a silver ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars onto the substrate with a carbon ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars so as to include the central heater bar, a pair of first outer heater bars, and a pair of second outer heater bars, the central heater bar is disposed between the first outer heater bars, the first outer heater bars are disposed between the second outer heater bars, the central heater bar is thinner than the first outer heater bars in a second direction substantially perpendicular to the first direction, and the first outer heater bars are thinner than the second outer heater bars in the second direction.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the central heater bar to be thinner than the outer heater bars at a central point between the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the central heater bar to be thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the two electrodes and/or the plurality of heater bars onto the substrate with conductive ink.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the two electrodes so as to be aligned on opposite sides of a microchannel extending through at least a portion of the substrate.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars so as to overlap a microchannel extending through at least a portion of the substrate.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars so as to overlap the microchannel in a direction approximately perpendicular to the direction of the microchannel.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the plurality of heater bars before printing the two electrodes.

In another embodiment, which may be used in combination with any other embodiment disclosed herein, the method includes printing the two electrodes to at least partially overlap the plurality of heater bars.

