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There are all kinds of inventions that make modern living possible, but some fly under the radar.
有各种各样的发明让生活更加现代化，但一些却没有引起大家的注意。
Some so much so that we've only just figured out how they truly work. Case in point: the washing machine.
其中有一些，我们甚至到现在才了解它的真正原理，例如：洗衣机。
Because apparently, no published paper was able to totally explain how these things got your clothes clean; not until 2018.
因为显然，没有一篇已发表的论文能够完全解释这些东西是如何让你的衣服变得干净的；直到2018年。
Now, to be clear, it's not like we had no idea how these machines worked.
现在，需要明确的是，我们并不是对这些机器完全不了解。
The oldest washing machines that resemble our modern appliances date back to the 19th century,
与现代家用电器相似的最古老的洗衣机可以追溯到19世纪，
so these things have been around for quite a while.
所以这些东西还是有些年头的。
And for years, we've had a really good understanding of how they use soap
多年来，我们已经很好地了解了这些机器是如何利用肥皂
and detergent to get stuff off the surface of your clothes. Soap is a surfactant, which is short for surface active agent.
以及清洁剂清洗衣服表面的。肥皂是一种表面活性剂，全称为surface active agent。
That means its molecules can attach to two substances that don't normally interact, for example, oil and water.
这意味着其分子可以吸附在两种通常不相互作用的物质上，比如油和水。
Usually, one end of the molecule is hydrophobic, meaning it repels water,
通常分子的一端是疏水的，可以抵御水，
and the other end is hydrophilic and regularly bonds with water.
另一端是亲水的，通常会与水相结合。
So, when soap is dumped into a big bath of water, the surfactant molecules group together to form spherical structures called micelles.
所以当肥皂被倒入一大浴缸的水中时，表面活性剂分子会聚集在一起形成一种叫做胶束的球状结构。
The hydrophilic ends stick out toward the water, and the hydrophobic ends hide inside.
亲水的一端朝水伸出，疏水端藏在里面。
When a micelle lands on a dirty section of fabric,
当胶束落在脏的织物上时，
the hydrophobic ends pop out and attach to the dirt, or whatever is soiling your clothes.
疏水端跳出来，吸附在脏东西上，或者任何弄脏你衣服的东西上。
Then, the hydrophilic ends pull the rest of the micelle off the fabric's surface,
然后亲水端将其余的胶束从织物表面拉出
and the micelle reforms with the soil it's "eaten" in its center.
并且胶束在其中心与“被吃掉”的脏物质发生变化。
Detergents like the ones we use for washing clothes use anionic surfactants,
像这样的我们用来洗衣服的洗涤剂利用的是阴离子表面活性剂，
meaning the hydrophilic end has a negative electrical charge.
这意味着亲水端带有负电荷。
But, while there are different types of surfactants, they generally all work the same way.
但是虽然有多种不同类型的表面活性剂，它们的原理都是一样的。
The reason washing machines spin everything around is to help the soap solution
洗衣机旋转的原因是为了帮助肥皂溶液
flow through your fabric and pick up all the dirt hiding in the crevices.
流过你的织物，把藏在缝里的污垢都洗掉。
But here's where the mystery came in: Water can't flow through every spot in your clothes.
但问题就来了：水无法穿透过衣服的每个角落。
That's because fabric is usually made of yarn, which is itself made of multiple fibers.
因为织物通常是由纱线制成的，而纱线本身是由多种纤维制成的。
Soap generally has no problem getting into inter-yarn pores, or the spaces between separate strands of yarn.
一般肥皂进入纱线间的孔隙或纱线之间的空隙是没有问题的。
But it does have a problem getting into intra-yarn pores, or the spaces between the fibers in a single strand.
但要进入纱线内的孔隙或是单股纤维之间的空隙就有问题了。
These pores are at least an order of magnitude smaller than the inter-yarn ones,
这些孔隙至少比纱线间的孔隙小一个数量级，
and only about 0.1 percent of the soap solution can actually get inside them, and even then, it doesn't get in all the way.
并且仅有约0.1%的皂溶液可以进去，但也不能完全进入。
Micelles actually get stuck in there and are only able to move when they're struck by nearby water molecules.
胶束会卡在那里，且只有当它们被附近的水分子撞击时才能移动。
According to the math, all of the micelles would eventually get knocked out,
根据数学计算，所有的胶束最终都会被清除出去
and that soap and dirt would go flowing down the drain. But this process would take several hours.
然后皂水和脏污都会流入下水道。但这一过程需要几个小时。
And that's just not how washing machines work. They get the soap and crud off your clothes in usually under one hour.
洗衣机就不是这样工作的。通常不用一小时，它们就能把你衣服上的洗衣皂和污垢洗掉。
This phenomenon was called the "stagnant core problem",
这一现象被称为“停滞的核心问题”，
and its what scientists hadn't been able to explain until that 2018 paper.
并且直到2018年的那篇论文，科学家们才能解释这一问题。
In their research, the authors learned that the solution to getting dirt out of those intra-yarn pores wasn't the soap, which is kind of surprising.
在他们的研究中，作者们了解到清洗纱线内孔隙的溶液并不是肥皂液，这挺让人惊讶的。
Instead, it was the rinse cycle, along with a process called diffusiophoresis.
反而是冲洗周期和一种被称为浓度梯度泳动的过程在起作用。
Diffusiophoresis is the movement of colloidal particles caused by a gradient.
浓度梯度泳动由梯度引起的胶体粒子的运动。
In other words, it's the movement of tiny particles suspended but not dissolved in a fluid.
换句话说，它是微小粒子的运动，这些粒子悬浮在液体中但不溶解。
When you swap out the soapy water with the clean stuff,
当你把肥皂水换成干净的东西时，
the surfactant micelles are way more concentrated in the fiber pores than they are elsewhere.
表面活性剂胶束在纤维孔隙中比在任何地方都集中。
And when you're using anionic surfactants, this creates an electric field
当你使用阴离子表面活性剂时，这会创造一个电场
that makes the micelles migrate out of those intra-yarn pores.
让胶束从纱线内部的孔隙中迁移出来。
In their paper, scientists figured this out by doing a series of experiments.
在他们的论文中，科学家通过一系列实验发现了这一点。
Instead of dirt, they used micrometer-sized, fluorescent balls,
他们用微米大小的荧光球代替污垢，
and they picked a standard detergent called sodium dodecyl sulfate.
并选择了一种叫做十二烷基硫酸钠的标准洗涤剂。
It also goes by sodium lauryl sulfate, and you can probably find it in most of the cleaning products you own.
也叫十二醇硫酸钠，并且你或许可以在大部分清洁用品中发现它。
The team did one trial with no detergent at all, just to see how much cleaning the water and agitation could do all by itself.
团队做了一次完全不使用清洁剂的试验，只为了看看仅靠清水和搅拌，能洗得多干净。
Then, they did a trial that rinsed sudsy fabric with detergent-filled water, and no diffusiophoresis was observed.
然后，他们做了一个试验，用充满清洁剂的水冲洗涂满肥皂的织物，并且没有观察到浓度梯度泳动。
Finally, their third run mimicked a regular wash/rinse cycle, where the soapy fabric was rinsed with clean water.
最后他们的第三次尝试模仿了常规的清洗/漂洗循环，用清水冲洗涂满肥皂的织物。
This time, the team observed that the fabric pores nearly emptied out after just 10 minutes of rinsing,
这一次，团队发现织物孔隙在仅十分钟后就冲洗干净了，
cleaning out the intra-yarn pores over 100 times faster than in the soapy run.
清除纱线内部孔隙的速度比肥皂清洗快100多倍。
So yeah, surfactants get the dirt off your clothes, but you need clean water to actually get dirt out of them.
所以没错，表面活性剂可以去除衣服上的污垢，但是你需要干净的水来去除污垢。
This research doesn't answer all the questions about cleaning your clothes,
该研究并没有回答所有关于清洗衣物的问题，
for example, why some stains are far more persistent than others, but it does have some worthwhile applications.
例如，为什么一些污渍比其他的更加持久，但它确实有一些有价值的应用。
With knowledge like this, we might be able to maximize detergent efficiency
有了类似这样的知识，我们或许能够最大限度地提高洗涤剂的效率
and minimize the amount of water and energy we use to do our laundry.
并尽量节省洗衣时的水电。
That would make washing machines, both in your home and in industry, much better for the planet.
这将让家用和工用洗衣机更加环保。
Which is kind of a big deal, considering how much water this process takes.
考虑到这个过程的用水，这一点意义重大。
On a different note, other research suggests that faster rinsing speeds could also create a better diffusiophoresis effect.
另一方面，其他研究表明，更快的冲洗速度也能产生更好的浓度梯度泳动效果。
So there may be turbo-charged washers in our future that get clothes clean even faster.
因此，未来可能会出现涡轮增压洗衣机，能更快地清洗衣物。
But, hey, as long as my laundry comes out smelling fresh, I'm all for it. Thanks for watching this episode of SciShow!
但只要洗出来的衣服香香的，我就完全支持。感谢收看本期《科学秀》！
If you want to learn more about laundry science, you can check out our episode about fabric brighteners.
如果想了解更多关于洗衣科学的知识，大家可以看看关于织物光亮剂的那一期视频。
Apparently, they don't just make the colors in your fabric more vibrant, they make your clothes glow.
显然，它们不仅能让布料的颜色更有活力，还能让衣服闪闪发光。
