New Method Uses Paper to Make Microfluidic Devices

Scientists start with paper having a hydrophobic or water-repellant coating, such as parchment paper or wax paper used for cooking. A laser is used to burn off the hydrophobic coatings in lines, dots, and patterns, exposing the underlying water-absorbing paper only where the patterns are formed. Having a patterned hydrophilic surface is needed for many detection methods in biochemistry, such as enzyme-linked immunosorbent assay, or ELISA, used in immunology to detect the presence of an antibody or an antigen in a sample

The innovation, which was developed by scientists at Purdue University (West Lafayette, IN, USA) represents a way to enhance commercially available diagnostic devices that use paper-strip assays like those that test for diabetes and pregnancy.

"With current systems that use paper test strips you can measure things like pH or blood sugar, but you can't perform more complex chemical assays," says Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering. "This new approach offers the potential to extend the inexpensive paper-based systems so that they are able to do more complicated multiple analyses on the same piece of paper. It's a generic platform that can be used for a variety of applications.”

Findings are detailed in a paper published online in the January 2011 edition of the journal Lab on a Chip.

Current lab-on-a-chip technology is relatively expensive because chips must be specifically designed to perform certain types of chemical analyses, with channels created in glass or plastic and tiny pumps and valves directing the flow of fluids for testing.

Chips are being used for various applications in medicine and research, measuring specific types of cells and molecules in a patient's blood, monitoring microorganisms in the environment and in foods, and separating biological molecules for laboratory analyses. But the chips, which are roughly palm-size or smaller, are difficult to design and manufacture.

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