Coordinating Multiple Droplets in Planar Array Digital Microfluidics Systems

Eric Griffith and Srinivas Akella

Rensselaer Polytechnic Institute

Low-cost, portable lab-on-a-chip systems capable of rapid automated biochemical analysis can impact a wide variety of applications including genetic analysis (medical diagnostics, prenatal and newborn testing, DNA fingerprinting), biological research (genomics, proteomics, glycomics, drug discovery), and biochemical sensing (pathogen detection, air and water monitoring, chemical explosives detection).

Digital microfluidics is a promising new technology that can dramatically improve processing of biochemical assays by offering tremendous flexibility and parallelism through software reconfigurability. The same hardware can be used for multiple analyses, even simultaneously. A digital microfluidic system (DMFS) typically consists of a planar array of cells with electrodes that control individual droplets of chemicals; the chemical analysis is performed by moving, mixing, and splitting droplets. Since the simultaneous coordination of tens or hundreds of droplets on the array is extremely difficult to program manually, algorithms to automatically enable the flexible operation of these devices are essential.

Our research focuses on algorithms to enable the automation of digital microfluidic system technology. We have developed array layout designs and algorithms to coordinate droplet operations, and demonstrated multiplexed analyses in a simulated DMFS. The animations below illustrate our algorithms in action. For details, please see our papers .

Based on figure from Duke University

The Components

Street		Connector		Intersection		Source		Sink		Work Area

Sample Animations

MPEG animations (if you don't want to download the DivX codec).

The animations below were recorded using the DivX codec.  It is available free at http://www.divx.com.

Click on an image to view the animation.

Droplet Mixing

Here blue and green droplets enter from the lower left.  They are mixed together into a yellow droplet.  When mixing is complete, the yellow droplet splits into two yellow droplets, which exit at the lower right.

PCR Reaction

The simplified analysis graph below outlines the mixing operations taking place in the animation. Each node is colored and shaped to match the droplet produced or introduced by that operation. The droplets enter from an array of sources along the left and exit at a sink in the lower right.

Multiple Simultaneous Reactions

This example demonstrates the PCR reaction being run in parallel with a smaller reaction. The droplets for the PCR reaction are squares and the droplets from the secondary reaction are diamonds. See the analysis graph below.