Micro-fluidic pump
View Patent ↗A micro-fluidic pump comprises one or more channels having an array of resistive heaters, an inlet, outlet and a substrate as a heat sink and a means of cooling the device. The pump is operated with a fire-to-fire delay and/or a cycle-to-cycle delay to control the pumping rate and minimize heating of liquid inside the pump during its operation.
1. A micro-fluidic pump, comprising:
a substrate;
a plurality of resistive heaters on the substrate each having a rectangular planar shape including a heater length and heater width, wherein a spacing between two adjacent said resistive heaters is in a range from about 1.5 to about 4.0 times said heater width;
a cover layer above and spaced from the resistive heaters defining a channel having a channel width with a volume in which fluid in the channel can flow from one heater to a next heater of the resistive heaters at a rate of over 0.1 μl/min. without escaping the cover layer except at an inlet or outlet to the channel; and
a flow feature layer on the substrate defining upstanding walls under the cover layer, wherein there exists a ratio of the channel width to the heater length in a range from about 1.0 to about 2.0.
2. The pump of claim 1 , wherein a minimum number of resistive heaters in the channel corresponds to a time required to cool down said one resistive heater to an initial temperature after having been activated and another time between activating two adjacent said resistive heaters.
3. The pump of claim 1 , wherein the resistive heaters electrically connect to circuitry for activation.
4. The pump of claim 1 , wherein the walls have a height in a range from about 10 to about 100 microns.
5. The pump of claim 4 , wherein the height is about 40 microns.
6. The pump of claim 1 , wherein the resistive heaters number at least nineteen resistive heaters adjacent to one another in the channel between said upstanding walls.
7. The pump of claim 1 , wherein the heater length and the channel width extend parallel to one another.
8. The pump of claim 1 , wherein the spacing between said each of the resistive heaters is substantially equidistant.
9. The pump of claim 1 , wherein the spacing of all the resistive heaters is symmetrical along the channel.
10. The pump of claim 1 , further including a liquid container.
11. The pump of claim 3 , wherein the circuitry is activated to keep the fluid in the channel at a temperature of about 50° C. or less.