Braille display drives biochip

By Kimberly Patch, Technology Research News

What do you get when you cross microscopic fluid-filled channels, computers, and Braille?

Researchers from the University of Michigan have adapted a configurable Braille display, which has a grid of vertically moving pins, to control the movement of fluids through the elastic capillary-like networks of microfluidic systems.

The method could eventually be used to culture and differentiate cells in a way that could augment or replace medical and pharmaceutical testing using animals. The work "opens the door to automated and programmable cell cultures on the miniature scale," said Wei Gu, a researcher at the University of Michigan.

Braille displays, like computer displays, represent words on a screen and can be refreshed, or changed. While a visual display uses pixels of color configured to represent groups of letters that can be read, the Braille display uses a grid of pins that move up and down to produce lines of Braille-alphabet letters that can be felt.

The researchers recognized that they could use the mechanism of computer-controlled vertical pins as the pumps and valves of a network made of elastic silicone rubber. "Small tunnels in silicone rubber are placed close to the surface of the rubber," said Gu. "Movable pins on the Braille display push against the surface of the rubber close to these tunnels and valve them closed mechanically," he said. "When three of these pins [move] in a particular sequence, peristaltic pumping is possible through the tunnel."

Peristaltic motion is also responsible for human digestion: the circular muscles of the gut wall periodically contract and relax in sequence to force food along the alimentary canal.

The researchers showed that it is possible to use the computer-controlled pins to switch among microfluidic actions: rapidly mixing fluid streams, flowing streams close together without mixing, and segmenting flows.

At the small scales typical of microfluidic systems like labs-on-a-chip, turbulence does not help mix fluids, making mixing a pair of liquids with the viscosity of water more like kneading dough than stirring cream into coffee. At the larger scale turbulence causes an initial mixing motion to continue. The lack of turbulence makes it more difficult to mix tiny amounts of liquids, but also makes it possible to flow tiny streams of fluid next to each other with little mixing.

The researchers use the system to compartmentalize groups of cells into subpopulations and culture them separately. "We used the fluid control to culture cells while controlling the fluidic environment around those cells," said Gu.

The system could eventually be used in any application that requires complex plumbing for cell processing or culture, said Gu.

Long-term, the researchers are aiming to use the system as a sort of animal-on-a-chip lab. "For example, we can grow miniature tissue samples -- liver, fat [or] muscle -- on a chip and have a blood-like media circulate through the mini-tissue in analogy to a human body," said Gu. "Using human cells, this can be a better model for drug/toxicity evaluations," he said. "It offers a different viewpoint than using a mouse or chimpanzee, which are also costly and economically unfeasible if you wanted to test hundreds of drug variations or combinations."

Eventually analytical computer components could be integrated onto the same chip. This would allow the animal-on-a-chip lab to conduct entire experiments, said Gu.

Gu's research colleagues were Xiaoyue Zhu, Nobuyuki Futai, Brenda S. Cho and Shuichi Takayama. The work appeared in the November 9, 2004 issue of the Proceedings of the National Academy of Sciences. The research was funded by the the Army Research Office (ARO), the National Science Foundation (NSF), the Whitaker Foundation, the Nathan Shock Center for Aging Research and the National Aeronautics and Space Administration (NASA).

Timeline:  3 years
Funding: Government, Private
TRN Categories:  Microfluidics and BioMEMS; Biotechnology
Story Type: News
Related Elements:  Technical paper, "Computerized Microfluidics Cell Culture Using Elastomeric Channels and Braille Displays," Proceedings of the National Academy Of Sciences, November 9, 2004


January 26/February 2, 2005

Page One

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