Passive pumps for microfluidic devices

A passive microfluidic pump fluidly connected to a microfluidic device, wherein the pump comprises:

• (a) a fluid inlet structured to fluidly connect to the microfluidic device;
• (b) a resistive region dimensioned to control fluid flow rate;
• (c) an absorbent region;
• and
• (d) an evaporation barrier enclosing the resistive region and optionally the absorbent region;
• wherein the resistive region comprises a first porous medium through which fluid flows from the inlet to the absorbent region, and a fluidly non-conducting boundary, and wherein the resistive region produces and maintains a predetermined fluid flow rate;
• wherein the absorbent region comprises a fluidly non-conducting boundary defining a volume of a second porous medium sized to absorb a predetermined volume of fluid imbibed from the resistive region,
• wherein a resistance to fluid flow through the resistive region is at least ten times greater than the resistance to fluid flow through the absorbent region, and
• wherein the microfluidic device comprises a microfluidic channel fluidly connecting a microfluidic fluid inlet to a microfluidic fluid outlet and wherein the microfluidic fluid outlet of the microfluidic device is fluidly connected to the fluid inlet of the passive microfluidic pump.

A passive microfluidic pump fluidly connected to a microfluidic device, wherein the pump comprises:

• (a) a fluid inlet structured to fluidly connect to the microfluidic device;
• (b) a resistive region dimensioned to control fluid flow;
• (c) an absorbent region configured such that the fluid flow rate stays effectively constant once a fluid front reaches the absorbent region;
• and
• (d) an evaporation barrier enclosing the resistive region and the absorbent region;
• wherein the resistive region comprises a first porous medium through which fluid flows from the inlet to the absorbent region, and a fluidly non-conducting boundary, and wherein the resistive region determines and maintains a constant, a step-increase, a step-decrease, or an oscillating fluid flow rate;
• wherein the absorbent region comprises a fluidly non-conducting boundary defining a volume of a second porous medium sized to absorb a predetermined volume of fluid imbibed from the resistive region,
• wherein a resistance to fluid flow through the resistive region is greater than the resistance to fluid flow through the absorbent region, and
• wherein the microfluidic device comprises a microfluidic channel fluidly connecting a microfluidic fluid inlet to a microfluidic fluid outlet and wherein the microfluidic fluid outlet of the microfluidic device is fluidly connected to the fluid inlet of the passive microfluidic pump.