Researchers from IBM Research in Zurich and the University Hospital of Basel in Switzerland developed a microfluidic device that uses capillary action to detect the presence of protein biomarkers for various disease types. The five square centimeter silicon-based lab-on-a-chip takes only 15 seconds to perform its analysis.
Here are the five functional stages of the device:
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Stage 1: A one microliter sample, 50 times smaller than a tear drop, is pipetted onto the chip, where the capillary forces begin to take effect.
Stage 2: These forces push the sample through an intricate series of mesh structures, which prevent clogging and air bubbles from forming.
Stage 3: The sample then passes into a region where microscopically small amounts of the detection antibody have been deposited. These antibodies have a fluorescent tag and similar to the antibodies within our body, they recognize the disease marker and attach to it within the sample. Only seventy picoliters (a volume one million times smaller than a tear) of these antibodies are used, making their dissolution in the passing sample extremely fast and efficient.
Stage 4: The most critical stage is called the 'reaction chamber' and it measures 30 micrometers in width and 20 micrometers in depth, roughly the diameter of a strand of human hair. Similar to a common pregnancy test, in this stage the disease marker that was previously tagged is captured on the surface of the chamber. By shining a focused beam of red light, the tagged disease markers can be viewed using a portable sensor device that contains a chip similar to those used by digital cameras, albeit this one being much more sensitive. Based on the amount of light detected, medical professionals can visually confirm the strength of the disease marker in the sample to determine the next course of treatment.
Stage 5: Less a stage and more a part of the entire process is the capillary pump. The capillary pump, which has a depth of 180 micrometers, contains an intricate set of microstructures, the job of which is to pump the sample through the device for as long as needed and at a regular flow rate, just like the human heart. This pump makes the test accurate, portable and simple to use. IBM scientists have developed a library of capillary pumps so that tests needing a variety of sample
Abstract in Lab on a Chip: Toward one-step point-of-care immunodiagnostics using capillary-driven microfluidics and PDMS substrates