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A capillary drinking straw could deliver the beverage to the lips without the time and energy-consuming suction that is needed in an ordinary straw to remove the air on each suck. Capillary action means the surface tension of the water does the work against gravity. A thinner straw entails less weight
to be lifted and its liquid is pulled higher by capillarity.
To lift a beverage through a 20 cm straw (about 8 inches) a 0.14 mm tube, the diameter of a thick human hair, is needed. To equal the area of a 5 mm diameter straw, some 1,333 tubes would be used. Packed together including the plastic walls, the tube arrangement would have a cross section of 1 cm^2 formed as a rectangle the size of three sticks of gum.
With reservation for the viscosity and particle size of drinks like a milk shake, the capillary strip straw would surely be a new advance in drinking pleasure.
Capillary arrays (middle of page)
http://www.us.schot...care/biotechnology/
[FarmerJohn, Feb 10 2005]
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Annotation:
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How long does it take for the liquid to climb the straw? That could be a very slow gin fizz. |
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Could this also be used for drip irrigation? |
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I couldn't find an equation for the meniscal velocity, but one can compare with blood collection capillary tubes that fill in seconds. |
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A liquid will not drip out of the top of a capillary straw by itself. |
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Any industrial applications for this? Could it be adapted to
syphon fuel and such like? do smaller capillaries carry
fluids beyond the 20cm mark? These drinking straws would
be expensive. can they be cleaned and reused? |
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[GL] They seem to exist for tasks such as DNA testing (link). An aid to siphoning, yes. Tree capillaries transport liquids many meters. "Expense" is not in the HB dictionary. |
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Wow, 6 years and no-one has pointed out that you would actually have to suck harder to get the same amount of liquid. Yes, surface tension does the work of raising the liquid, but you then have to do the equivalent work to remove it from the surface tension potential well, and additional work to overcome frictional losses. |
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The liquid's slumping out of the straw between sips would be better addressed by fitting a non-return valve to the base of the straw. |
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The advantage of self-priming, eliminating the initial delay, however, remains with the present idea. |
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This is a classic "why is my free lunch so expensive" paradox. You will need to suck harder to get the same fluid back out of the capillary tubes. I could illustrate but it would really be a waste of time. Just imagine that the tube causes lots of friction. |
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