Office of Technology Transfer – University of Michigan

Gravity Driven Pump with a Steady Flow Rate

Technology #2099


The need for device miniaturization has led to the advent of microfluidic devices. Often called lab-on-a-chip, microfluidics devices strive to perform procedures that are difficult to accomplish with larger scale technologies, as well as reduce time, labor, and cost associated with such techniques. Such devices usually require pumps to supply fluid through the microchannels. To date, most systems use mechanical or non-mechanical pumps, with which steady flow rate may be difficult to achieve. In addition, these pumps are costly and inconvenient to integrate with other microscale devices, and often have slow response times. While gravity-driven flow has been explored for microflulidics applications, conventional systems lead to decreased flow rates over time.


Researchers at the University of Michigan have developed a novel microfludics system that uses a microchannel and a gravity-driven pump. The pump consists of horizontally-oriented fluid reservoirs that supply the microchannels at a constant flow rate, which does not change as the pumped volume increase over time. In this system, the fluid reservoirs are connectable or connected to the microfluidics device, and their horizontal orientation maintains the hydrostatic pressure asserted by the liquid in the supply reservoir to be relatively constant. The microfluidic device contains at least one microchannel through which fluid flows due to hydrostatic pressure exerted by a difference in height (relative to gravitational field) between the supply reservoir and the microchannel. The rate of flow produced by the pumps of the present invention is adjusted by altering the height of the supply reservoir above the microfluidics device.

Applications and Advantages


  • Microfluidics devices
  • In vitro screening of pharmacological-nl-agents
  • Analysis of flow/shear stress-related-nl-phenomena
  • Study of embryo development
  • Cell sorting


  • Simple and economical to produce
  • Provides a relatively constant and optionally-nl-adjustable flow rate, without an external-nl-power source