Typical "on-chip" pumping technologies require external equipment to operate and control the fluid flow, restricting their applicability to lab environments. For example, pneumatic pumps require compressed gas sources, and DC electro-osmotic pumps require high voltage power supplies. AC electroosmotic pumps, however, have the potential to be contained and controlled completely on-chip. The basic operational principle is given in the illustration to the right. Arrays of asymmetric electrode pairs are fabricated inside microchannels, and an AC voltage signal is applied. This creates an electrokinetic force that will produce net fluid flow through the microchannels.
Advantages of an AC Micropump
There are a wide range of micropump technologies that have the potential for pumping small amounts of fluid on-chip. We have chosen AC electroosmotics as the platform for developing an integrated pump based on the following important advantages:
As part of our preliminary work on the project, we have developed a complex model of the working pump using FEM Multiphysics simulation software. These simulations are an important tool that allow investigation and optimization of the numerous parameters governing the fluid flow; an example is shown below.
By performing a sensitivity analysis on the applied peak voltage, estimations on the velocities achievable with this pump design can be made. Shown below is an example of the fluid velocity profile achieved at various applied voltages.
The market for microfluidic devices has seen rapid growth in recent years. In 2005 it was worth an estimated $2.9 billion, growing to $3.2 billion in 2006, and projected to be $6.2 billion by 2011 . Microfluidic devices have applications in countless fields, such as lab-on-a-chip devices for drug discovery and delivery, and portable sensors for monitoring the presence of specific molecules.
The micropump being developed in this project will be an important enabling technology for many areas of microfluidics. In particular, portable sensors would benefit greatly from a low power, cheap, completely on-chip micropump. Remote sensing of water quality, for detection of harmful agents and acts of bioterrorism, could be realized. Also, cheap and portable sensors are greatly desired for researchers working outside of their labs, as it is often costly, time consuming, and difficult to transport samples from the field back to the lab.
Microfluidic systems are used often in laboratories for many purposes, such as studying many chemical reactions in parallel, or examining the behavior of cells and other biological molecules in various environments. In any case, these setups require expensive microfluidic pumps that are controlled with various sensors, valves, and tubing, all of which are located externally. This can make such setups complicated and expensive. Being able to integrate the pump and flow controls within the microfluidic chip would allow an all in one microfluidics package to be offered to researchers. The technology being developed in this project is an important step in realizing the all in one microfluidics system.