Braille display drives biochip
Technology Research News
do you get when you cross microscopic fluid-filled channels, computers,
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
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
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