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  • Watch what happens when I place some small drops of food coloring on to this slide.

    看我在玻片上滴下一些食用色素會發生什麼事情

  • Some are attracted to each other and merge,

    一些會相互吸引然後結合

  • while others repel and chase each other.

    而有些則會排斥與追逐彼此

  • It looks just like the tiny world of micro-organisms, but why?

    看起來就像個微生物世界,為何會這樣?

  • Well if you want to try this out for yourself

    如果你想自己試試

  • You need to get some ordinary food coloring and dilute it with distilled water using a pipette.

    你要有一般的食用色素,以滴管加入蒸餾水稀釋

  • Then pass the microscope slide through a flame for about thirty seconds.

    接著用火焰烘烤顯微鏡載玻片約 30 秒

  • Let it cool, and then put some drops of different concentration on to the slide.

    待冷卻後,在玻片上滴幾滴不同溶液

  • You'll find that drops of similar concentration attract each other and merge

    你會發現濃度相似的溶液水滴相互吸引並結合

  • while drops of different concentrations chase each other.

    而濃度不同溶液水滴則會相互追逐

  • You can draw guides on the slide using permanent marker, which is hydrophobic

    你還能拿疏水性的麥克筆畫出引道

  • and set up long distance pursuits.

    讓水滴沿著追趕

  • Or you can find that drops of similar concentration attract each other

    或者看著相似溶液的水滴仍然互相吸引

  • despite the hydrophobic barriers.

    即使有著疏水性的屏障

  • But how is this possible just using ordinary food coloring and water?

    不過只是水跟食用色素為什麼會有這麼奇妙的現象?

  • Well the key is evaporation.

    關鍵就在蒸發

  • Each drop is constantly evaporating, so around it is an envelope of vapour.

    每個水滴都不斷地在蒸發,所以會被一層水氣包覆

  • The rate of evaporation depends on the humidity around the drop

    蒸發的快慢取決於周遭的濕度

  • so the drier the air is, the faster the rate of evaporation.

    周圍的空氣越乾燥,水滴蒸發的越快

  • So when any two drops are close enough

    所以當兩個水滴很靠近彼此

  • the humidity between them is greater than than the humidity around them,

    兩者中間地帶的溼度就會大於外圍

  • and therefore there's more evaporation around the droplets

    所以外圍會蒸發的比較快

  • then in-between them,

    中間蒸發的較慢

  • and this pushes them together.

    兩者之間的壓力差便把他們推向對方

  • So differential evaporation makes the droplets attract,

    所以蒸發速率差會讓水滴互相吸引

  • but that's not the whole story.

    不過還不只如此

  • Food coloring is a mixture of mainly two molecules,

    食用色素主要是由兩種分子所組成

  • water and propylene glycol.

    水還有丙二醇

  • These two liquids mix well so we say they are miscible,

    這兩種液體可以均勻的混合,所以是可以混溶的

  • but they have different properties.

    可是他們有不同的性質

  • For example, water evaporates more readily because its lighter,

    舉例來說,水分子比較輕所以蒸發較快

  • and it has a stronger surface tension due to hydrogen bonding.

    而且他也有更強的表面張力,因為它具有氫鍵

  • And this is important because interesting things happen when there are gradients in surface tension.

    這很重要,因為當存在表面張力梯度時, 有趣的事會發生

  • For example, if I add some pepper to this bowl of water to allow me to see the motion,

    來做個實驗,我先在這碗水裡加些胡椒好看見水的流動

  • and then I add a little dab of soap, right in the middle,

    然後在水面中央沾一些清潔劑

  • you see that all of the water rushes outwards,

    你可以看到所有的水都往外衝

  • and this is because soap has a lower surface tension than water.

    這是因為清潔劑的表面張力比水小

  • You can think of it a bit like a tug of war.

    你可以把他想成是在拔河

  • Before I added the soap all of those water molecules were pulling on each other equally,

    在我加入清潔劑之前, 所有水分子都是以同樣的力道互相拉扯

  • but once I add the soap molecules in the middle,

    不過當我在中間加入一些清潔劑分子

  • their weaker surface tension means the water molecules around them are pulling

    他們較弱的表面張力代表周圍水分子拉扯的力道

  • harder on each other than the soap is,

    比中間的清潔劑還要強

  • and so they rush outwards away from that spreading soap drop.

    所以水分子才會快速地被往外拉,遠離中間那滴清潔劑

  • And this motion is called "Marangoni flow."

    這種現象稱為"馬倫哥尼效應"

  • And a similar thing is actually happening with our food coloring droplets.

    在我們的色素水滴裡面其實也有類似的效應

  • If you have drops of similar concentration they attract each other due to the higher humidity in-between them,

    兩個濃度相近的水滴會因為彼此之間濕度較高

  • and they merge.

    所以互相吸引融合

  • And although drops of different concentration also attract each other

    而雖然濃度不同的水滴也會因為同樣的原因互相吸引

  • they don't merge when they come into contact.

    他們在接觸時不會互相融合

  • This is because the water in the lower concentration drop

    因為濃度較低的水滴裡面的水分子

  • pulls together and away from the drop with the higher concentration of propylene glycol,

    會拉扯並遠離丙二醇濃度較高的水滴

  • just like with the soap and water.

    就像水與清潔劑那樣

  • And differential evaporation drives the two drops forwards.

    而蒸發速率差則推動兩個水滴前進

  • It is fascinating to watch these droplets and think about how closely their motion mimics life.

    看著這些水滴的運動跟生命體是如此相像 實在是非常有趣

  • Living organisms seek out molecules like food,

    有機生命體會去接近特定的分子,像是食物

  • and this is a process known as "chemotaxis."

    這個過程稱為"趨化性"

  • But what these droplets are doing is really not all that dissimilar,

    而這跟這些水滴的行為其實有點像

  • in fact its been called artificial chemotaxis.

    事實上這種現象被稱為"人工趨化性"

  • And as amazingly life like as their motion appears,

    而雖然這些水滴運動跟生命現象的相似度高的驚人

  • in a way, I think it shouldn't be all that surprising.

    某方面來說,這其實是理所當然的

  • After all, evolution began with the natural tendencies of molecules:

    畢竟生命演化的起源,就是這些化學分子不同的性質

  • to form and break apart, to attract and repel.

    互相結合或崩解,互相吸引或排斥

  • And then over billions of years of refinement through natural selection,

    而經過天擇數十億年的精煉

  • evolution has produced bodies whose utilisation of

    演化出了複雜的生命體

  • these natural tendencies of molecules appears miraculous.

    利用這些分子的不同性質表現出看似奇蹟的生命現象

  • And its that, that we call life.

    這就是我們所謂的生命

  • I tried using slides that hadn't been passed through a flame

    我有嘗試過使用沒燒過的玻片

  • and then I couldn't get the drops to move.

    不過水滴就不動了

  • So on researching this further I found out that passing

    經過更深入的研究,我發現

  • the microscope slide through the flame creates a high energy sufrace

    把玻片放在火焰上燒會製造出一個高能量的表面

  • and what that means is, the flame is essentially breaking open some of the bonds -

    意思是說,火焰會打斷一些化學鍵

  • the glass bonds in the surface of this slide -

    那些玻璃玻片表面的化學鍵

  • and when you put the droplet on top,

    而當你滴上水滴

  • Its those open bonds, its that high energy surface that

    那些被打開的化學鍵製造出的高能量表面

  • draws some of the water molecules away from the droplet.

    會把一些水分子從水滴中拉出來

  • And that actually makes the water molecule more likely to evaporate.

    而這會讓水分子蒸發得更快

  • But as just happened right there, some of the microscopes,

    不過就像剛剛發生的這樣

  • some of the microscope slides have shattered.

    有些玻片會碎掉

  • And so you should be particularly careful when doing this procedure,

    所以你在加熱的時候應該特別小心

  • obviously heating them up to a very high temperature causes them to expand a lot

    加熱到高溫明顯的會使他們劇烈膨脹

  • and when they contract again as they're cooling, well then,

    當他們冷卻下來要收縮的時候

  • they sometimes break apart because of those stresses.

    過程中的壓力有時會造成玻璃碎裂

Watch what happens when I place some small drops of food coloring on to this slide.

看我在玻片上滴下一些食用色素會發生什麼事情

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