Chemists in Taiwan have developed a bubble-activated micropump that can transport blood on a microchip. The pump could improve point-of-care disease diagnosis, they claim.

The micropump uses air bubbles to drive blood through the channel

Sheng-Hung Chiu and Cheng-Hsien Liu from the National Tsing Hua University, Hsinchu, Taiwan, electrolytically generated hydrogen and oxygen bubbles from water and used them to control a micropump.

Micropumps provide the pressure that drives fluids through channels in lab-on-a-chip microsystems. Although many micropumps have been developed, most require high temperatures or voltages, which can damage blood cells. Electrochemically activated pumps are known but they alter the pH of blood, harming the cells.

The new design overcomes these limitations by confining the pump's electrolysis reaction to an electrolyte-filled side channel on the chip, explains Liu. Its separation from the main, blood-containing channel stops it altering the main channel's pH.

When Liu and Chiu applied a voltage to the pump's platinum electrodes, the electrolytically generated bubbles increased the pressure in the side channel. This pushed forward an air bubble between the electrolyte and the blood, moving the blood in the main channel. When Liu turned off the voltage, the electrolytic bubbles escaped through vents in the side channel and the air bubble retreated. Using two side channels in sequence produced a flow of liquid through the channel.

'Separating the electrolytic solution from the working solution by a trapped air bubble is a clever design,' comments Abraham Lee, an expert in microfluidic chip processors at the University of California at Irvine, US.

Liu says he hopes that the pump will be 'integrated with other multiple components to form microfluidic systems for lab-on-a-chip systems, biochips and drug delivery'.

Nicola Wise

Enjoy this story? Spread the word using the 'tools' menu on the left or add a comment to the Chemistry World blog.