Not just in smartphones, but in supermarkets, ATMs, and even airplane seats.

處處可見觸控螢幕。不只是智慧型手機， 還有超市、ATM、甚至飛機座位。

And you may have noticed that not all touchscreens are the same.

你也許發現不是所有觸控螢幕都一樣。

The old-school touchscreens can be pretty tough to use -- sometimes it feels more like

舊型觸控螢幕相當難用─有時候感覺比較像

a push-really-hard-screen instead of a touchscreen.

「按超大力螢幕」而非觸控螢幕。

On the other hand, certain smartphones and computer monitors are really responsive to

反觀某些智慧型手機或電腦螢幕，

many different touch patterns.

就對各種不同觸控模式相當敏感。

There are lots of different technologies out there, but they're all trying to achieve

這包含了很多種科技，但其目的一致：

the same goal: sending precise electrical signals from specific locations on the screen.

從螢幕上的特定地點傳送電子訊號。

One of the most widely used types is the resistive touchscreen, where you have to physically

最常用的技術之一就是「電阻式觸控面板」，你必須

push and bend the screen to make it work.

用力壓螢幕使它彎曲才能運作。

Resistive touchscreens are made of two separate layers:

電阻式觸控面板分成兩層：

The top layer is made from a flexible and transparent material, such as polyethylene,

上層由有彈性的透明材料製成，好比聚乙烯，

which is a common plastic used to make things like soda bottles.

這是一種常拿來做為汽水罐的塑膠。

And the bottom layer is made of something more rigid, like a sheet of glass.

而下層則由較硬的東西製作，例如玻璃板。

To make the screen work, both of these layers are thinly coated with some sort of metal

為了運作，兩層材料都必須塗上能導電的薄層金屬，

compound that conducts electricity, like indium tin oxide -- which is commonly used because

例如氧化銦錫，因為它能透光。

it's transparent.

例如氧化銦錫，因為它能透光。

These layers are also separated by tiny insulating dots, which /don't/ conduct electricity,

這幾層材質還會被微小的絕緣節點隔開，稱為隔球，

called spacers.

它們分隔螢幕，確保不會觸發假訊號。

They keep the screens apart to make sure there aren't any false touch signals.

它們分隔螢幕，確保不會觸發假訊號。

When the screen is on, a small voltage is applied across the screen in both the horizontal

螢幕啟動時，水平與垂直方向都會產生微小的電壓，

and vertical directions.

當螢幕啟動，水平與垂直方向都會產生微小的電壓，

As soon as you push down on the flexible screen with anything, like your finger or a stylus,

當你用任何東西按壓彈性螢幕，例如手指或筆尖，

it connects the two layers together.

會讓兩層材料連結。

This changes the voltage, and a small processor connected to the screen can calculate exactly

這股電壓改變經過連結螢幕的處理器計算，可精確得出

where you pressed in X and Y coordinates.

按壓位置的X,Y座標。

These resistive touchscreens are pretty affordable and durable.

這種電阻式觸控面板相當廉價且耐用，

So, they're useful for things like credit card readers in grocery stores, where you

因此它們常用於雜貨店的信用卡讀卡機，

need to capture touch data of a messy signature -- over and over again.

這種需要捕捉混亂簽名軌跡無數次的狀況。

But they can be a little frustrating to use if you don't push hard enough.

但你若壓得不夠力可能會有點挫折感，

Plus, they normally can't understand multiple-touches at the same time – so they're no good

另外它們也無法同時多點觸控，因此對於

for two-finger zoom or more complex tasks.

兩根手指縮放螢幕或更複雜的動作束手無策。

That's why these days, most smartphones rely on capacitive touchscreens, where your

因此近年來多數智慧手機都倚賴「電容式觸控面板」，

finger becomes a key part of the electronics.

你的手指成了電路的關鍵。

There are different kinds of capacitive touchscreens, and they can vary from device to device.

根據裝置的不同，會採用不同技術的電容式螢幕，

But one basic design is a sheet of glass containing a grid of hair-thin lines of a conductive

但一種基本款式是一片玻璃，包含細如髮絲的導電金屬

metal, like indium tin oxide.

交錯成格子狀，如氧化銦錫。

The grid lines in one direction are called the driving lines, which provide a constant

其中一個方向的線條稱為驅動線，提供恆定電流。

electric current.

其中一個方向的線條稱為驅動線，提供恆定電流。

And the lines in the other direction are called the sensing lines, which detect this electric

另一方向的線條稱為感測線，偵測驅動線之電流。

current.

另一方向的線條稱為感測線，偵測驅動線之電流。

At every point where the sensing lines and the driving lines cross, there will be a specific

感測線和驅動線的每個交會點， 都會形成獨立的靜電場，

electrostatic field, which is registered as neutral by the processor in your smartphone

由電腦標示為電中性。

or computer.

由電腦標示為電中性。

But that all changes when something conductive comes along and touches it -- like your finger.

但任何導體，如你的手指碰觸螢幕時情況為之一變。

See, the human body has a natural capacitance, which means our bodies can conduct electric

人體是個天然電容，也就是能導電，

current, and can store electric charge.

還能夠保存電荷。

So when your finger touches the screen, the charge in the screen is drawn around that

因此當你用手指碰觸螢幕，螢幕上的電荷會環繞該點

point, distorting that electrostatic field.

扭曲該處靜電場。

The electricity doesn't actually /flow/ through your finger.

電流並未真的流經手指。基本上靜電場會感應到

Basically, the electrostatic field feels the effects of your electric charge and redistributes

你帶的電荷引發的效應並自我重整。

itself accordingly.

任何微小的改變都會被處理器偵測，

Even really small changes are detected by the processor, which can then interpret the

解讀成你的動作模式，可能是點擊或滑動。

patterns you're making – whether it's a tap or a slide.

由於線路極細，電容式觸控非常準確，

Because the lines of the grid are so thin, capacitive touchscreens are super accurate,

有些版本可以同時感應多重觸碰。

and some versions can process multiple touches at a time.

但戴上手套螢幕就感應不到，因為布無法導電，

But they won't work if you have gloves on -- because the cloth isn't conductive, unless

除非手套指尖上有特殊金屬纖維。

your gloves have those special fingertips with metal fibers inside.

另外，汗水等物會影響螢幕上的電流，

Plus, something like sweat can affect how electricity is conducted across the screen,

因為其含有鹽分(能導電)。

because it's full of salts.

一切都攸關材質是否能影響螢幕產生的電流。

It's all about the materials that can affect the electrostatic field generated inside your

一切都攸關材質是否能影響螢幕產生的電流。

screen.

因此下回當你在智慧型手機上打字， 或在平板電腦看網路論壇，

So next time you're texting on a smartphone or scrolling through internet forums on a

記住：你是螢幕運作電路的一部分。

tablet, just remember: you're actually a part of the electronics making it work.

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別忘了到 youtube.com/scishow訂閱！

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