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Medical tests might soon look more like pregnancy tests

Rapid medical diagnostics might soon look more like paper strips.

That's right. Scientists out of Purdue University have figured out how to make medical tests look more like the paper strip tests that are used to detect pregnancy or diabetes.

The paper strips out in stores today are simple though, and are only capable of testing pH levels or blood sugar. But with this new way of making paper strips with lab-on-chip technology, it's possible to measure much more, like the types of cells or identify specific molecules in a patient's blood.

The Purdue researchers used paper that you could buy at any store, and made microfluidic devices that could be used for fast, medical diagnostics. To fashion the channels on the paper, the researchers used a laser to design the paper-based microfluidic device.

"Any paper with a hydrophobic surface coating (e.g., parchment paper, wax paper, palette paper) can be used for this purpose," the researchers wrote. Having a patterned hydrophlic surface is critical, so the laser can etch off the coating and allow the paper to be exposed and ready to soak up the chemical and biological reagents needed for the test.

The paper strips had arrays of dots that were soaked in a chemical that would turn blue when it came into contact with blood. And it worked. When the researchers exposed the strips to blood, it turned blue to indicate the presence of blood.

The channel was constructed so liquid could move naturally from one end to the other. A strategically placed reactant would change colors, and the paper would show if the result is positive or negative.

This isn't the first time researchers have tried to make paper-based microfluidics, but Purdue engineering professor Babak Ziaie this his way is better. Ziaie said in a statement:

Our process is much easier because we just use a laser to create patterns on paper you can purchase commercially and it is already impregnated with hydrophobic material. It's a one-step process that could be used to manufacture an inexpensive diagnostic tool for the developing world where people can't afford more expensive analytical technologies.

The researchers showed that paper strips could work for more complex systems by showing its effectiveness in detecting the presence of hemoglobin. Someday, the strips might test for a slew of different compounds and biological markers.

The speed and cost of such devices would benefit from rapid color changes that could be read by electronic readers. However, the applications go beyond medicine and it's feasible to think that paper microfluidics could even help in environmental tracking or be used for research purposes in the lab.

To be honest, I'm amazed that microfluidics can be made out of paper. My first research project in college used a microfluidic channel made from lithography and poly(dimethylsiloxane) and required a syringe pimp.

Photo: Birck Nanotechnology Center, Purdue University

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