Microfluidic Diagnosis Tool Made from Paper

Lab-on-a-chip devices, a relatively new technology in the world of portable diagnostic tools, promise both mobility and accurate microfluid analysis. The problem is that they cannot be mass produced since they are made out of expensive materials such as silicon, glass or plastics, and are extremely hard to manufacture, often requiring tiny pumps and valves. This could be easily solved with the help of a new invention created at Harvard's Whitesides Research Group; a paper material that has the capability of making microfluidics technology much cheaper than it is today.

"It's the first example I've heard of paper microfluidics. It's really clever because it uses paper as a substrate, which is universally available", says Albert Folch, a bioengineer at the University of Washington.

Test papers are generally common but they can also get very expensive, because they use special chemical reagents. Whitesides researchers believe that by minimizing the amount of reagents and the surface of the paper material, manufacturing costs can be drastically reduced. Basically, they would have the same functionality as any traditional paper test, being able to tell whether someone is suffering from kidney failure or an infectious disease by simply wetting it with a small amount of fluid.

The fluid moves naturally through the paper, much in the same way wine spreads through a paper napkin. The paper also contains a hydrophobic polymer channel that directs the fluid to the reagents, thus coloring the paper. The color can then be matched to a color key, similar to the one used in pH test paper to reveal the result of the diagnostic.

The test paper in the image above has three ramifications, housing the wells with reagents, two for a glucose assay and the third for a protein assay. The test paper simulates the sophisticated components of a lab-on-a-chip device, such as sensors, analyzers, pumps and power sources with the help of its natural capillarity.

Creating channels in the material is no longer required, since the test paper takes advantage of its own network of channels. The hydrophobic polymers simply isolate the channels that are not required for the correct functioning of the device. "What's really clever about this system is that they've actually patterned the whole volume of the substrate. The paper itself forms a network of capillaries", Folch explains.