New paper will lead to cheap medical devices
Click: 1505  Date: 2013-05-31 10:11:00  Comefrom:
New paper will lead to cheap medical devices
TURNING A NEW PAGE: Georgia Tech professor Dennis Hess and graduate research assistant Lester Li work on the new paper samples
US researchers have created a new type of paper that repels liquids, including water and oil; work could lead to new generation of biomedical diagnostics devices.

How about a paper material that wouldn't be affected by water, oil or any other variety of liquids? Researchers at the Georgia Institute of Technology have created a new type of paper that repels liquids, including water and oil.

The researchers say the modified paper could be used as the foundation for a new generation of inexpensive biomedical diagnostics in which liquid samples would flow along patterns printed on the paper using special hydrophobic ink and a desktop printer.

The paper was created by modifying the underlying network of cellulose fibres, etching off surface 'fluff', and applying a thin chemical coating. The material uses nanometer - and micron-scale structures - plus a surface fluorocarbon to turn old-fashioned paper into an advanced material.

"Paper is a very heterogeneous material composed of fibbers with different sizes, different lengths and a non-circular cross-section," Dennis Hess, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering, said in an article posted on the university's website

"We believe this is the first time that a superamphiphobic surface - one that repels all fluids - has been created on a flexible, traditional and heterogeneous material like paper."

The new paper, which is both water and oil repelling, can be made from standard softwood and hardwood fibres. Producing the new paper begins with breaking up cellulose fibres into smaller structures using a mechanical grinding process. As in traditional paper processing, the fibres are then pressed in the presence of water - but then the water is removed and additional processing is done with the chemical butanol. Use of butanol inhibits the hydrogen bonding that normally takes place between cellulose fibres, allowing better control of their spacing.

The second step involves using an oxygen plasma etching process - a technique commonly used in the microelectronics industry - to remove the layer of amorphous fluffy cellulose surface material, exposing the crystalline cellulose nanofibrils.

Finally, a thin coating of a fluoropolymer is applied over the network of cellulose fibres. In testing, the paper was able to repel water, motor oil, ethylene glycol and n-hexadecane solvent.

"We have shown that we can do the operations necessary for a microfluidic device," Hess was quoted as saying, "We can move the droplet along a pattern, split the droplet and transfer the droplet from one piece of paper to another. We can do all of these operations on a two-dimensional surface."

HOW THEY TWEAKED SIMPLE PAPER

The 'advanced paper' was created by modifying the underlying network of cellulose fibres, etching off surface 'fluff', and applying a thin chemical coating.

The material uses nanometer - and micronscale structures - plus a surface fluorocarbon to turn old-fashioned paper into an advanced material.
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