It’s an increasingly common sight in hospitals around the world: a nurse measures our height, weight, blood pressure, and attaches a glowing plastic clip to our finger. Suddenly, a digital screen reads out the oxygen level in our bloodstream. How did that happen? How can a plastic clip learn something about our blood… without a blood sample?
這是在全世界的醫院 愈來愈常見的景象: 護士量我們的身高、體重、血壓 和夾一個會發光的塑膠夾 在我們指頭。 瞬間,一個數位螢幕顯示了 我們的血氧濃度。 怎麼會這樣呢? 沒有血液檢體, 塑膠夾是如何判讀血液呢? 關鍵在此:
Here’s the trick: our bodies are translucent, meaning they don’t completely block and reflect light. Rather, they allow some light to actually pass through our skin, muscles, and blood vessels. Don’t believe it? Hold a flashlight to your thumb.
身體是半透明的, 這表示他們不能完全阻擋及反射光線。 反而是身體可讓一些光穿透皮膚、 肌肉和血管。 不信嗎? 拿一個手電筒照大拇指, 可看到其實光是可協助 探測身體的內部。
Light, it turns out, can help probe the insides of our bodies.
以剛剛那個醫用指夾為例,
Consider that medical fingerclip— it’s called a pulse oximeter. When you inhale, your lungs transfer oxygen into hemoglobin molecules, and the pulse oximeter measures the ratio of oxygenated to oxygen-free hemoglobin. It does this by using a tiny red LED light on one side of the fingerclip, and a small light detector on the other.
它叫「脈搏血氧儀」。 當吸氣時,肺將氧氣 轉到血紅蛋白的分子上, 脈搏血氧儀量出 「氧合血紅素」 和「去氧血紅素」的比例。 它在指夾的一側,運用了小型紅色的 「發光二極體 (LED)」光源, 而指夾另一側有個小型光感測器。
When the LED shines into your finger, oxygen-free hemoglobin in your blood vessels absorbs the red light more strongly than its oxygenated counterpart. So the amount of light that makes it out the other side depends on the concentration ratio of the two types of hemoglobin.
當 LED 光穿透指頭時, 血管中的去氧血紅素 吸收紅色光的能力, 遠遠超過氧合血紅素。 所以有多少光從另一側出來, 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. For one patient, a saturation reading of ninety-five percent corresponds to a healthy oxygen level, but for another with smaller arteries, the same reading could dangerously misrepresent the actual oxygen level.
但任何兩個病患的指頭內 血管大小都不相同, 對一位病患而言, 95% 的血氧飽和度 是個健康血氧濃度值, 而對另一位動脈較小的病患, 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. Light comes in a vast spectrum of wavelengths, and infrared light lies just beyond the visible colors. All molecules, including hemoglobin, absorb light at different efficiencies across this spectrum. So contrasting the absorbance of red to infrared light provides a chemical fingerprint to eliminate the blood vessel size effect.
這可利用第二個 紅外線波長的 LED 光來矯正。 光有極多不同的波長, 而且紅外光是在可見光之外。 所有的分子,包括血紅蛋白, 在光譜中的吸光率各不相同, 所以比較紅光與紅外光被吸收多少 而產生的「化學指紋」圖案,
Today, an emerging medical sensor industry is exploring all-new degrees
可去除血管大小不同的誤差。
of precision chemical fingerprinting, using tiny light-manipulating devices no larger than a tenth of a millimeter. This microscopic technology, called integrated photonics, is made from wires of silicon that guide light— like water in a pipe— to redirect, reshape, even temporarily trap it.
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, 他們運用各種不超過 0.1公釐的微小光學元件, 這種顯微技術 稱為「積體光學」, 它採用矽製的線來導引光── 正如水管導引水── 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, is a light trapper that enhances chemical fingerprinting. When placed close to a silicon wire, a ring siphons off and temporarily stores only certain waves of light— those whose periodic wavelength fits a whole number of times along the ring’s circumference. It’s the same effect at work when we pluck guitar strings. Only certain vibrating patterns dominate a string of a particular length, to give a fundamental note and its overtones.
一種環狀共振裝置, 是一種圓形的矽線, 它能截取光 而提高化學指紋的清晰度。 把這裝置靠近另一矽線時, 它可吸取和暫時貯存特定的光波── 只要這光的週期波長 其整數倍數中的一個值 等於這環的周長即可。 彈吉他時也是相同原理。 一條特定長度的弦, 只有在某些震動型式下, 才能產生出「基音」和「泛音」。
Ring resonators were originally designed to efficiently route different wavelengths of light— each a channel of digital data— in fiber optics communication networks. But some day this kind of data traffic routing may be adapted for miniature chemical fingerprinting labs, on chips the size of a penny. These future labs-on-a-chip may easily, rapidly, and non-invasively detect a host of illnesses, by analyzing human saliva or sweat in a doctor’s office or the convenience of our homes.
環狀共振裝置最初設計 是為有效地導引不同波長的光── 每道光都是數字數據── 行走於光纖通訊網路中。 可是未來某天, 這種數據流量傳輸 可適用在微型化學指紋檢驗室中, 在一分錢大小的晶片上。 這未來的晶片檢驗室 可以輕易迅速地 且非侵入性地檢驗很多疾病, 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。
Human saliva in particular mirrors the composition of our bodies’ proteins and hormones, and can give early-warning signals for certain cancers and infectious and autoimmune diseases. To accurately identify an illness, labs-on-a-chip may rely on several methods, including chemical fingerprinting, to sift through the large mix of trace substances in a sample of spit.
特別是人體唾液 與體內蛋白質和賀爾蒙的組成相似, 且能提供某些癌症、感染 及自體免疫性疾病的早期預警。 為了準確診斷疾病, 晶片檢驗室可能仰賴多種方法, 包括化學指紋, 以便在唾液檢體中 篩出許多重要的物質。 唾液中的各種生物分子 可吸收相同波長的光──
Various biomolecules in saliva absorb light at the same wavelength— but each has a distinct chemical fingerprint. In a lab-on-a-chip, after the light passes through a saliva sample, a host of fine-tuned rings may each siphon off a slightly different wavelength of light and send it to a partner light detector. Together, this bank of detectors will resolve the cumulative chemical fingerprint of the sample. From this information, a tiny on-chip computer, containing a library of chemical fingerprints for different molecules, may figure out their relative concentrations, and help diagnose a specific illness.
但每個分子 會產生不同的化學指紋。 在晶片檢驗室, 光穿透唾液檢體後, 許多精調過的環 各會吸取不同波長的光, 而後將光轉到 其對應的光感測器上。 這組感測器會共同做出 這檢體的化學指紋。 利用這個訊息, 一個微小晶片上的電腦 貯存了很多不同分子的化學指紋, 可算出每個分子的濃度, 從而協助診斷特定的疾病。
From globe-trotting communications to labs-on-a-chip, humankind has repurposed light to both carry and extract information. Its ability to illuminate continues to astonish us with new discoveries.
從全球通訊到晶片檢驗室, 人類利用光來傳輸及獲得訊息。 光的照明能力不斷地帶給我們 令人驚訝的新發現。