Self-powered blood analysis chip could deliver diagnosis in minutes
The researchers took advantage of the laws of microscale physics to speed up processes that may take hours or days in a traditional lab. They note, for example, that the sediment in red wine that usually takes days to years to settle can occur in mere seconds on the microscale.
The SIMBAS biochip uses trenches patterned underneath microfluidic channels that are about the width of a human hair. When whole blood is dropped onto the chip’s inlets, the relatively heavy red and white blood cells settle down into the trenches, separating from the clear blood plasma. The blood moves through the chip in a process called degas-driven flow.
Schematic of the tether-free SIMBAS chip that shows some of the functional elements, such as the blood loading area, the plasma separation microtrenches, detection sites and the suction flow structures. Credit: Ivan Dimov.
For degas-driven flow, air molecules inside the porous polymeric device are removed by placing the device in a vacuum-sealed package. When the seal is broken, the device is brought to atmospheric conditions, and air molecules are reabsorbed into the device material. This generates a pressure difference, which drives the blood fluid flow in the chip.
In experiments, the researchers were able to capture more than 99 percent of the blood cells in the trenches and selectively separate plasma using this method. The team demonstrated the proof-of-concept of SIMBAS by placing into the chip’s inlet a 5-microliter sample of whole blood that contained biotin (vitamin B7) at a concentration of about 1 part per 40 billion. The biodetectors in the SIMBAS chip provided a readout of the biotin levels in 10 minutes.
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