You are more transparent than you think - Sajan Saini

譯者: Ann Chen 審譯者: Helen Chang

It’s an increasingly common sight in hospitals around the world:

這是在全世界的醫院 愈來愈常見的景象：

a nurse measures our height, weight, blood pressure,

護士量我們的身高、體重、血壓

and attaches a glowing plastic clip to our finger.

和夾一個會發光的塑膠夾 在我們指頭。

Suddenly, a digital screen reads out the oxygen level in our bloodstream.

瞬間，一個數位螢幕顯示了 我們的血氧濃度。

How did that happen?

怎麼會這樣呢？

How can a plastic clip learn something about our blood…

沒有血液檢體， 塑膠夾是如何判讀血液呢？

without a blood sample?

Here’s the trick:

關鍵在此：

our bodies are translucent,

身體是半透明的，

meaning they don’t completely block and reflect light.

這表示他們不能完全阻擋及反射光線。

Rather, they allow some light to actually pass through our skin,

反而是身體可讓一些光穿透皮膚、

muscles, and blood vessels.

肌肉和血管。

Don’t believe it?

不信嗎？

Hold a flashlight to your thumb.

拿一個手電筒照大拇指，

Light, it turns out, can help probe the insides of our bodies.

可看到其實光是可協助 探測身體的內部。

Consider that medical fingerclip—

以剛剛那個醫用指夾為例，

it’s called a pulse oximeter.

它叫「脈搏血氧儀」。

When you inhale, your lungs transfer oxygen into hemoglobin molecules,

當吸氣時，肺將氧氣 轉到血紅蛋白的分子上，

and the pulse oximeter measures the ratio of oxygenated to oxygen-free hemoglobin.

脈搏血氧儀量出

「氧合血紅素」 和「去氧血紅素」的比例。

It does this by using a tiny red LED light on one side of the fingerclip,

它在指夾的一側，運用了小型紅色的 「發光二極體 (LED)」光源，

and a small light detector on the other.

而指夾另一側有個小型光感測器。

When the LED shines into your finger,

當 LED 光穿透指頭時，

oxygen-free hemoglobin in your blood vessels absorbs the red light

血管中的去氧血紅素 吸收紅色光的能力，

more strongly than its oxygenated counterpart.

遠遠超過氧合血紅素。

So the amount of light that makes it out the other side

所以有多少光從另一側出來，

depends on the concentration ratio of the two types of hemoglobin.

取決於這兩種血紅蛋白的比例。

But any two patients will have different-sized blood vessels in their fingers.

但任何兩個病患的指頭內 血管大小都不相同，

For one patient, a saturation reading of ninety-five percent

對一位病患而言， 95% 的血氧飽和度

corresponds to a healthy oxygen level,

是個健康血氧濃度值，

but for another with smaller arteries,

而對另一位動脈較小的病患，

the same reading could dangerously misrepresent the actual oxygen level.

相同的數值可能危險地誤判 他的真正血氧濃度。

This can be accounted for with a second infrared wavelength LED.

這可利用第二個 紅外線波長的 LED 光來矯正。

Light comes in a vast spectrum of wavelengths,

光有極多不同的波長，

and infrared light lies just beyond the visible colors.

而且紅外光是在可見光之外。

All molecules, including hemoglobin,

所有的分子，包括血紅蛋白，

absorb light at different efficiencies across this spectrum.

在光譜中的吸光率各不相同，

So contrasting the absorbance of red to infrared light

所以比較紅光與紅外光被吸收多少

provides a chemical fingerprint to eliminate the blood vessel size effect.

而產生的「化學指紋」圖案，

可去除血管大小不同的誤差。

Today, an emerging medical sensor industry is exploring all-new degrees

現在，新的醫學感測器產業在研究

各種不同精確化學指紋的方法，

of precision chemical fingerprinting,

using tiny light-manipulating devices no larger than a tenth of a millimeter.

他們運用各種不超過 0.1公釐的微小光學元件，

This microscopic technology,

這種顯微技術

called integrated photonics,

稱為「積體光學」，

is made from wires of silicon that guide light—

它採用矽製的線來導引光──

like water in a pipe—

正如水管導引水──

to redirect, reshape, even temporarily trap it.

使其改變方向、改變形狀、 甚至暫時截住它。

A ring resonator device, which is a circular wire of silicon,

一種環狀共振裝置， 是一種圓形的矽線，

is a light trapper that enhances chemical fingerprinting.

它能截取光 而提高化學指紋的清晰度。

When placed close to a silicon wire,

把這裝置靠近另一矽線時，

a ring siphons off and temporarily stores only certain waves of light—

它可吸取和暫時貯存特定的光波──

those whose periodic wavelength fits a whole number of times

只要這光的週期波長 其整數倍數中的一個值

along the ring’s circumference.

等於這環的周長即可。

It’s the same effect at work when we pluck guitar strings.

彈吉他時也是相同原理。

Only certain vibrating patterns dominate a string of a particular length,

一條特定長度的弦， 只有在某些震動型式下，

to give a fundamental note and its overtones.

才能產生出「基音」和「泛音」。

Ring resonators were originally designed

環狀共振裝置最初設計

to efficiently route different wavelengths of light—

是為有效地導引不同波長的光──

each a channel of digital data—

每道光都是數字數據──

in fiber optics communication networks.

行走於光纖通訊網路中。

But some day this kind of data traffic routing

可是未來某天， 這種數據流量傳輸

may be adapted for miniature chemical fingerprinting labs,

可適用在微型化學指紋檢驗室中，

on chips the size of a penny.

在一分錢大小的晶片上。

These future labs-on-a-chip may easily, rapidly,

這未來的晶片檢驗室 可以輕易迅速地

and non-invasively detect a host of illnesses,

且非侵入性地檢驗很多疾病，

by analyzing human saliva or sweat in a doctor’s office

採用分析唾液或汗液，

且是在醫生診間 或在我們自己家中做。

or the convenience of our homes.

Human saliva in particular

特別是人體唾液

mirrors the composition of our bodies’ proteins and hormones,

與體內蛋白質和賀爾蒙的組成相似，

and can give early-warning signals for certain cancers

且能提供某些癌症、感染 及自體免疫性疾病的早期預警。

and infectious and autoimmune diseases.

To accurately identify an illness,

為了準確診斷疾病，

labs-on-a-chip may rely on several methods,

晶片檢驗室可能仰賴多種方法，

including chemical fingerprinting,

包括化學指紋，

to sift through the large mix of trace substances in a sample of spit.

以便在唾液檢體中 篩出許多重要的物質。

Various biomolecules in saliva absorb light at the same wavelength—

唾液中的各種生物分子 可吸收相同波長的光──

but each has a distinct chemical fingerprint.

但每個分子 會產生不同的化學指紋。

In a lab-on-a-chip, after the light passes through a saliva sample,

在晶片檢驗室， 光穿透唾液檢體後，

a host of fine-tuned rings

許多精調過的環

may each siphon off a slightly different wavelength of light

各會吸取不同波長的光，

and send it to a partner light detector.

而後將光轉到 其對應的光感測器上。

Together, this bank of detectors will resolve

這組感測器會共同做出

the cumulative chemical fingerprint of the sample.

這檢體的化學指紋。

From this information, a tiny on-chip computer,

利用這個訊息， 一個微小晶片上的電腦

containing a library of chemical fingerprints for different molecules,

貯存了很多不同分子的化學指紋，

may figure out their relative concentrations,

可算出每個分子的濃度，

and help diagnose a specific illness.

從而協助診斷特定的疾病。

From globe-trotting communications to labs-on-a-chip,

從全球通訊到晶片檢驗室，

humankind has repurposed light to both carry and extract information.

人類利用光來傳輸及獲得訊息。

Its ability to illuminate continues to astonish us with new discoveries.

光的照明能力不斷地帶給我們 令人驚訝的新發現。