Microfluidic device with constant heater uniformity
Inventors
Raghunathan, Ashwin • Lee, Steve • Revilla, Ryan Alan • Patel, Tej Rushikesh
Assignees
Publication Number
US-11344886-B2
Publication Date
2022-05-31
Expiration Date
2040-01-24
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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.
Core Innovation
The invention disclosed is a screen-printed heater design for a microfluidic test card that ensures uniform heating of a fluid sample within a microchannel to cause polymerase chain reaction (PCR). In this design, the heater includes two electrodes positioned on opposite sides of the microchannel and a plurality of heater bars electrically connecting these electrodes. A central heater bar is disposed between outer heater bars and is thinner than them in a direction approximately parallel to the microchannel, resulting in higher electrical resistance in the central heater bar.
The background problem addressed by the invention concerns thermal non-uniformity in heaters used on microfluidic test cards for PCR. Traditional screen-printed heaters exhibit significant temperature gradients due to non-uniform current density, such as a 20-degree difference over a 6 mm square area, which compromises the precise temperature control needed for PCR. This non-uniformity arises because current preferentially flows through paths of least resistance, usually the center of the heater, causing uneven heating.
The invention solves this problem by varying the width of heater bars so that the central heater bar has a higher resistance than outer heater bars. This variation in heater bar dimensions and resistance forces current to distribute more evenly across the heater, producing a more uniform temperature profile along the microchannel. The heater bars may be diamond-shaped or have other shapes but maintain the progressively increasing widths away from the central heater bar. The electrodes may be printed with silver ink and heater bars with carbon ink on a printed substrate layer bonded to the test card substrate.
Claims Coverage
The patent includes one independent claim relating to a microfluidic test card with a specifically designed printed heater, featuring inventive aspects related to heater bar geometry and configuration.
Heater with two electrodes aligned on opposite sides of a microchannel
A heater printed on a substrate layer includes two electrodes positioned on opposite sides of a microchannel extending through at least a portion of a substrate layer.
Plurality of heater bars electrically connecting electrodes with central heater bar thinner than outer heater bars
The heater comprises a plurality of heater bars electrically connecting the two electrodes, 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.
The claims focus on a test card having a heater arrangement with electrodes flanking a microchannel and a configuration of heater bars varying in thickness to achieve uniform heating, particularly emphasizing a thinner central heater bar than outer bars.
Stated Advantages
Ensures constant heater uniformity by controlling the electrical path and resistances of the heater bars.
Provides substantially uniform temperature across the microchannel, essential for precise PCR temperature control.
Reduces power consumption compared to alternative heater designs due to lower total resistance.
Documented Applications
Heating a fluid sample to cause polymerase chain reaction (PCR) within a microfluidic test card.
Point-of-care in vitro diagnostic tests, including nucleic acid amplification tests (NAATs) for early stage infection detection.
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