MIT Technology Review is reporting that researchers at Harvard are using paper as the building block material for creating small microfluidic devices, potentially allowing to make cheap disposable diagnostic tests.
A pinprick of blood or drop of urine soaked up at the edge of the Whitesides device moves naturally through the paper, in much the way that wine will spread through a paper napkin. But the paper is treated with a hydrophobic polymer, which directs the liquid along prescribed channels. Once the liquid reaches the wells at the ends of the channels, it interacts with reagents, turning the paper different colors. The colors can be matched to those on a color key, much as they are in a pH test. One test design that looks like a miniature, three-branched, geometric tree might have wells at the end of two branches for a glucose assay and one at the end of the third for a protein assay, for example.
The design dispenses with expensive components common in conventional microfluidic devices: chemical reactions that color parts of the paper replace sophisticated sensors and analyzers, while using paper’s natural capillary action to absorb liquids avoids the need for external pumps or power sources. Diagnostics for All–a spinoff cofounded by Whitesides and Harvard visiting scholar Hayat Sindi, with the support of partners from MIT–is commercializing the technology.
Instead of etching channels into a material, as most microfluidics designers do, Whitesides and Sindi were able to take advantage of the network of channels inherent in paper; the hydrophobic polymer simply seals off the channels that the researchers don’t want to use. “What’s really clever about this system is that they’ve actually patterned the whole volume of the substrate,” Folch explains. “The paper itself forms a network of capillaries.”
More at MIT Tech Review…