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.
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.
"This prep work of separating the blood components for analysis is done with gravity, so samples are naturally absorbed and propelled into the chip without the need for external power," said Dimov.
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.
"That can be roughly thought of as finding a fine grain of sand in a 1700-gallon sand pile," said Dimov.
The biodetectors in the SIMBAS chip provided a readout of the biotin levels in 10 minutes.
"Imagine if you had something as cheap and as easy to use as a pregnancy test, but that could quickly diagnose HIV and TB," said Benjamin Ross, a UC Berkeley graduate student in bioengineering and study co-author. "That would be a real game-changer. It could save millions of lives."
|Contact: Sarah Yang|
University of California - Berkeley