Microfluidic device with constant heater uniformity
11344886 · 2022-05-31
Assignee
Inventors
- Ashwin Raghunathan (Santa Ana, CA, US)
- Steve Lee (Mission Viejo, CA, US)
- Ryan Alan Revilla (Costa Mesa, CA, US)
- Tej Rushikesh Patel (Carlsbad, CA, US)
Cpc classification
B01L2200/12
PERFORMING OPERATIONS; TRANSPORTING
B01L3/502707
PERFORMING OPERATIONS; TRANSPORTING
B01L2300/1811
PERFORMING OPERATIONS; TRANSPORTING
B01L3/502715
PERFORMING OPERATIONS; TRANSPORTING
B01L2300/0816
PERFORMING OPERATIONS; TRANSPORTING
B01L7/52
PERFORMING OPERATIONS; TRANSPORTING
B01L2300/12
PERFORMING OPERATIONS; TRANSPORTING
International classification
B01L3/00
PERFORMING OPERATIONS; TRANSPORTING
G01N35/00
PHYSICS
B01L7/00
PERFORMING OPERATIONS; TRANSPORTING
G01N33/00
PHYSICS
Abstract
A heater for a microfluidic test card is disclosed herein. In a general example embodiment, 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.
Claims
1. A test card for analyzing a fluid sample, comprising: 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 including a heater printed on the printed substrate layer so as to align with at least a portion of the microchannel, the heater including: 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 including a central heater bar disposed between outer heater bars, wherein the central heater bar is thinner than the outer heater bars in a direction approximately parallel to the microchannel.
2. The test card of claim 1, wherein the at least one substrate layer includes a plurality of bonded layers.
3. The test card of claim 1, wherein the electrodes are printed onto the printed substrate layer with a silver ink.
4. The test card of claim 1, wherein the plurality of heater bars is printed onto the printed substrate layer with a carbon ink.
5. The test card of claim 1, wherein 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, wherein the central heater bar is disposed between the first outer heater bars, wherein the first outer heater bars are disposed between the second outer heater bars, wherein the central heater bar is thinner than the first outer heater bars in the direction approximately parallel to the microchannel, and wherein the first outer heater bars are thinner than the second outer heater bars in the direction approximately parallel to the microchannel.
6. The test card of claim 1, wherein the central heater bar is thinner than the outer heater bars at a central point between the two electrodes.
7. The test card of claim 1, wherein the central heater bar is thinner than the outer heater bars at respective points of contact with at least one of the two electrodes.
8. The test card of claim 1, wherein the central heater bar is thinner than the outer heater bars at respective portions aligned with the microchannel.
9. The test card of claim 1, wherein the plurality of heater bars each includes a central diamond shape and two protruding ends, wherein the protruding ends overlap with the two electrodes to place the two electrodes in electrical communication with each other.
10. The test card of claim 1, wherein the central heater bar includes two or more central heater bars.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Embodiments of the present disclosure will now be explained in further detail by way of example only with reference to the accompanying figures, in which:
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DETAILED DESCRIPTION
(15) Before describing in detail the illustrative system and method of the present disclosure, it should be understood and appreciated herein that the present disclosure relates to a test card for use with a rapid, high sensitivity and high specificity, low complexity diagnostic system using nucleic acid amplification and capable of operating in low resource settings with minimal user training. The system is configured, for example, to cause and analyze a polymerase chain reaction (“PCR”) within the test card, particularly in the early stages of infection, using a low-cost microfluidic platform employing PCR with a modified DNA polymerase. In an embodiment, the test card is configured to receive about 10 μL of whole blood, the equivalent to a drop of blood obtained from a finger stick. In another embodiment, the fluid sample can be serum, urine, saliva, tears and/or the like.
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(17) In an embodiment, a vacuum source can be applied to the outlet port 30. When a negative pressure is applied to the outlet port 30, the vacuum pressure pulls the fluid sample from the mixing chamber 26 through fluid microchannel 34 so that the fluid sample can be analyzed through analysis port 32 while residing within a target zone of the microchannel 34. The capture port 28 is configured to capture fluid from the fluid sample before the fluid flows to the outlet port 30. In the illustrated embodiment, the capture port 28 is sized to allow fluid to build up before it can reach the outlet port 30 to prevent the fluid from being sucked out of the outlet port 30 by the vacuum pressure applied to the outlet port 30. In an embodiment, the capture port 28 can include a porous material, which can act like a sponge to absorb any excess fluid and prevent fluid from escaping from test card 10 due to mishandling.
(18) As illustrated in
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(20) In the illustrated embodiment, the printed substrate layer 102 is printed onto the bottom surface of bottom substrate layer 12, before or after the bottom substrate layer 12 is bonded to one or more of channel layer 14, middle substrate layer 16, adhesive layer 18, and top substrate layer 20. As illustrated, the printed substrate layer 102 may be printed with a conductive ink 104 and a dielectric ink 106. The conductive ink 104 forms the electrical components of test card 10, whereas the dielectric ink 106 serve as protective, non-conductive coating to encapsulate the electrical components. The conductive ink 104 may become the electrical components once it is cured, for example, by heat or ultraviolet light. In an embodiment, one or more layers of conductive ink 104 is printed and then cured, and then one or more layers of dielectric ink 106 is printed and cured. In another embodiment, both the conductive ink 104 and the dielectric ink 106 are printed, and then both the conductive ink 104 and the dielectric ink 106 are cured. In another embodiment, several alternating layers of conductive ink 104 and dielectric ink 106 are printed to create multiple levels of conductive elements.
(21) In an embodiment, the printed circuit layer 102 is screen printed on the bottom surface of bottom substrate layer 12 through a screen made of a stainless steel or a polymer mesh. A hardened emulsion can be used to block out all areas of the screen except for the desired print pattern for the conductive ink 104 and/or dielectric ink 106, so that the conductive ink 104 and/or dielectric ink 106 is pushed through the screen in the desired print pattern.
(22) In the illustrated embodiment, the conductive ink 104 is printed to form a heater 100, as well as electrodes 120, 122 upstream and downstream of the heater 100 along microchannel 34. The conductive ink 104 may also form electrodes 124, which receive current from an analyzer device for controlling activation of the electrodes 120, 122 and the heater 100. The conductive ink 104 may further form electrical lines 126 connecting the electrodes 124 with the electrodes 120, 122 and/or the heater 100. The electrodes 120 and the electrodes 122 may be used to determine whether a fluid sample has flowed through fluid microchannel 34 so that the heater 100 may be used to heat the fluid to cause a PCR within the microchannel. In an embodiment, the electrodes 120, 122 utilize a changing dielectric constant as fluid flows through microchannel 34 to determine whether fluid has flowed therethrough, as the dielectric constant differs considerably when there is liquid in the microchannel at the electrodes 120, 122. Test card 10 also includes screen printed electrodes 124, which are in electrical communication with heater 100 and electrodes 120,122 via electrical lines 126. By placing a current source (from the analyzer device) in conductive communication with the electrodes 124, the current source can activate heater 100 and/or electrodes 120,122.
(23) As illustrated in
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(26) In an embodiment, the electrodes 110 may be formed of silver ink, while the heater bars 112 may be formed of carbon ink. In an alternative embodiment, the electrodes 100 and the heater bars 112 may be formed of the same or a different material, for example, silver ink, carbon ink, another conductive ink, or another electrically conductive material besides a cured ink.
(27) In the illustrated embodiment, the plurality of heater bars 112 includes a central heater bar 112a, first outer heater bars 112b, and second outer heater bars 112c. In the illustrated embodiment, each of central heater bar 112a and outer heater bars 112b, 112c is formed with a central diamond shape 114 (shown as 114a, 114b, 114c) and two protruding ends 116 (shown as 116a, 116b, 116c). The protruding ends 116 overlap with the electrodes 110 (shown as first electrode 110a and second electrode 110b) to place the electrodes 110 in electrical communication with each other. Although five heater bars 112 are shown in the illustrated embodiment, it should be understood by those of ordinary skill in the art that more or less heater bars may be used. The electrodes 110 may be printed either before or after the plurality of heater bars 112 so that the electrodes 110 and the plurality of heater bars 112 overlap.
(28) In the illustrated embodiment, each of the plurality of heater bars 112 increases in width in the y-direction from first electrode 110a to a central point 118 (shown as 118a, 118b, 118c) and then decreases in width in the y-direction from the central point 118 to second electrode 110b, creating a diamond shape with a largest width in the y-direction at central point 118. It is envisioned that other shapes could be used, for example, an oval shape that omits the sharp points at central point 118 but maintains a largest width at central point 118. Example embodiments of other shapes are illustrated at
(29) In the illustrated embodiment, central heater bar 112a is thinner in the y-direction than outer heater bars 112b, 112c, giving central heater bar 112a a higher resistance than the outer heater bars 112b, 112c. As illustrated, the central heater bar 112a is thinner in the y-direction at central point 118a of the diamond shape and also at each protruding end 116a than outer heater bars 112b, 112c at 118b, 118c and 116b, 116c, respectively.
(30) In an embodiment, the width W.sub.1 of protruding ends 116a of central heater bar 112a in the y-direction may be about 0.30 mm, the width W.sub.2 of protruding ends 116b of outer heater bars 112b in the y-direction may be about 0.45 mm, and the width W.sub.3 of protruding ends 116c of outer heater bars 112c in the y-direction may be about 0.60 mm. In another embodiment, W.sub.2 may be any width greater than W.sub.1, and W.sub.3 may be any width greater than W.sub.2. In another embodiment, W.sub.2 may be about 1.5×W.sub.1, and W.sub.3 may be about 1.33×W.sub.2 or about 2×W.sub.1. In another embodiment, W.sub.2 may be about 1× to 2×W.sub.1, and W.sub.3 may be about 1× to 2×W.sub.2. Those of ordinary skill in the art will recognize that other dimensions are possible.
(31) In an embodiment, the width W.sub.4 of the diamond or other shape of central heater bar 112a at central point 118a in the y-direction may be about 1.00 mm, the width W.sub.5 of the diamond or other shape of outer heater bars 112b at central point 118b in the y-direction may be about 1.20 mm, and the width W.sub.6 of the diamond or other shape of outer heater bars 112c at central point 118c in the y-direction may be about 1.30 mm. In another embodiment, W.sub.5 may be any width greater than W.sub.4, and W.sub.6 may be any width greater than W.sub.5. In another embodiment, W.sub.5 may be about 1.2×W.sub.4, and W.sub.6 may be about 1.1×W.sub.5 or about 1.3×W.sub.4. In another embodiment, W.sub.5 may be about 1× to 2×W.sub.4, 1× to 1.5×W.sub.4 or 1.1× to 1.3×W.sub.4, while W.sub.6 may be about 1× to 2×W.sub.5, 1× to 1.5×W.sub.5 or 1× to 1.3×W.sub.5. Those of ordinary skill in the art will recognize that other dimensions are possible.
(32) In an embodiment, each of the heater bars 112 may have a same length L.sub.1 in the x-direction. For example, L.sub.1 may be 6.00 mm. In an embodiment, the length L.sub.2 of each electrode 110 in the x-direction may be about 1.60 mm, and the width W.sub.7 of each electrode 110 in the y-direction may be about 7.50 mm.
(33) As further illustrated, the width of the outer heater bars 112b, 112c in the y-direction at central points 118b, 118c and protruding ends 116b, 116c progressively increases as the distance from central heater bar 112a increases in the y-direction. That is, the width of outer bars 112b in the y-direction at central point 118b and/or protruding end 116b is greater than the width of central bar 112a in the y-direction at central point 118a and/or protruding end 116a, respectively. Likewise, the width of outer bars 112c in the y-direction at central point 118c and/or protruding end 116c is greater than the width of outer bars 112b in the y-direction at central point 118b and/or protruding ends 116b, respectively.
(34) By using a heater with the same or similar structure as shown in
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(36) In contrast,
(37) It should be understood that the disclosed heater design may be utilized with other materials besides cured conductive inks. For example, another conductive material such as a metal may be sized and/or shaped as shown to achieve the same advantages.
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(41) In the illustrated embodiments, the plurality of heater bars 112 are printed with the same type of conductive ink and in the same general shape, and the size of the plurality of heater bars is used to cause the central heater bar 112a to have the greatest resistance, with the resistance of the outer heater bars 112b, 112c progressively decreasing as the distance from central heater bar 112a increases. That is, central heater bar 112a has the greatest resistance, first outer heater bars 112b have less resistance than central heater bar 112a, and second outer heater bars 112c have less resistance that first outer heater bars 112b. It is also envisioned, however, that the size of heater bars 112a, 112b, 112c may be the same or similar, and the overall shape or materials for each heater bar may be altered so that central heater bar 112a has the greatest resistance, first outer heater bars 112b have less resistance that central heater bar 112a, and second outer heater bars 112c have less resistance that first outer heater bars 112b. For example, the shape of all heater bars could be the same or similar, and the material used for central heater bar 112a could cause central heater bar 112a to have the greatest resistance, the material used for first outer heater bars 112b could cause first outer heater bars 112b to have less resistance than central heater bar 112a, and the material used for second outer heater bars 112c could cause second outer heater bars 112c to have less resistance that first outer heater bars 112b.
(42) It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
(43) Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
(44) The terms “a” and “an” and “the” and similar referents used in the context of the disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided herein is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the disclosure otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the disclosure.
(45) The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
(46) Groupings of alternative elements or embodiments of the disclosure disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.
(47) Preferred embodiments of the disclosure are described herein, including the best mode known to the inventors for carrying out the disclosure. Of course, variations on those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects those of ordinary skill in the art to employ such variations as appropriate, and the inventors intend for the disclosure to be practiced otherwise than specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
(48) Specific embodiments disclosed herein may be further limited in the claims using consisting of or consisting essentially of language. When used in the claims, whether as filed or added per amendment, the transition term “consisting of” excludes any element, step, or ingredient not specified in the claims. The transition term “consisting essentially of” limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s). Embodiments of the disclosure so claimed are inherently or expressly described and enabled herein.
(49) Further, it is to be understood that the embodiments of the disclosure disclosed herein are illustrative of the principles of the present disclosure. Other modifications that may be employed are within the scope of the disclosure. Thus, by way of example, but not of limitation, alternative configurations of the present disclosure may be utilized in accordance with the teachings herein. Accordingly, the present disclosure is not limited to that precisely as shown and described.