Researchers have long sought a wireless solution to power biomedical devices. Theoretically, magnetic fields can penetrate the skin to induce a current to charge the implanted device [1]. This capability could be a game-changer, eliminating the need of repeated surgeries to replace pacemaker batteries [2], and the infection risk associated with percutaneous wire insertion to power left ventricular assist devices (mechanical pumps for patients with advanced heart failure) [3]. Nevertheless, before the wireless charging technology can be commercialized in biomedical devices, some technical challenges still need to be overcome, such as misalignment between coils and burn injury caused by the highpower transmission [2, 4]. Wireless charging systems could be a future direction for electric cars as well. Mercedez-Benz has already been offering a wireless charging option in a car model back in 2017 [5]. Recently, the leading electric car company Tesla has also expressed interest in developing their own wireless charging technology [6]. However, infrastructural support, such as setting up charging stations with charging pads, is crucial to the promotion of the use of wireless charging. This may explain the general reluctance of car manufacturers to incorporate wireless technology into their products [6]. It is a chicken and egg situation: The motivation of car companies to invest in wireless technology is driven by the demand of electric cars, which, however, is now hindered by the accessibility to public charging. Although a lot of development is still due, engineers have conceived some futuristic ideas in city planning. Detroit has built the first wireless charging road in the US with electromagnetic coils installed underground for pilot testing [7]. While driving down the 400-meter road, the car battery can be charged through inductive charging. This could be a solution to extend the range of electric vehicles. This is just a glance at what wireless charging could do. In a desire to make technology better and smarter, developers take on the responsibility to make our lives easier without wires. From homes to high-tech endeavors, more and more devices go wireless. What’s next? 無線技術是新潮流，科技進步使我們能擺脫電線的纏 繞，讓我們享受到以無線充電座或支架為手機充電的便利 體驗。你有想過無線充電器如何運作嗎？答案也許比你想 像的簡單得多！ 無線充電又稱為感應充電，運作原理基於電磁學和電磁 感應範疇中一些物理學原理。我們第一個要了解的是安培定 律，它表明導體中的電流會產生與其強度成正比的磁場。如 果我們為一個螺線管（螺旋線圈）接上電源，螺線管就會變 成一塊電磁鐵，兩端會根據電流方向一端成為南極，另一端 成為北極。 這就是安裝在充電座裡的發射線圈。當發射線圈插上電 源後，電流會通過線圈使其成為電磁鐵。如果接上交流電， 電子的流動方向會不停改變，使電磁鐵的兩極不斷互換，從 而產生不斷變化的磁場。 接下來是第二個原理：法拉第電磁感應定律。這個由米 高．法拉第（Michael Faraday）於1831年發現的定律指出 變化中的磁場可以感生出稱為電動勢的電壓，它可以驅使電 流在導體內流動。 如果我們利用這個原理，將一個接收線圈安裝到我們想 要充電的設備中，這個線圈就會接收到不斷變化的磁場，並 產生電動勢，最終感生出電流通過設備。現在我們不就是能 無線傳輸電流了嗎？由於智能手機和手錶只能用直流電充 電，因此有種稱為整流器的電子零件可以透過限制電流方 向，將感生而來的交流電轉換成直流電。 許多人可能不知道，無線充電並不僅被用於手機充電，研 究人員亦一直尋求為醫療儀器無線供電的方案。理論上，磁 場可以穿透皮膚並感生電流為已植入體內的儀器充電 [1]。 這個原理未來可能會帶來革命性的改變，讓使用心臟起搏器 的患者不再需要接受重複手術以更換電池 [2]，亦能使植入 左心室輔助裝置（供末期心臟衰竭患者用的機械泵）的患者 不再需要透過皮下導線供電，從而避免相關感染風險 [3]。 然而，在應用無線充電技術的醫療儀器商品化之前，設計人 員仍需克服一些技術挑戰，例如線圈之間的錯位問題和高功 率傳輸造成的燒傷等 [2, 4]。 無線充電系統亦可能是電動車的未來方向。平治 （Mercedez-Benz）早在 2017 年就已經為旗下一款汽車型號 提供無線充電選項 [5；] 最近電動車公司的領頭羊特斯拉（Tesla） 也表示對開發自家無線充電技術感興趣 [6]。可是，建設基礎設 施對推廣無線充電至關重要，例如設立更多設置充電板的充電 站等，這某程度上解釋了汽車製造商普遍不願意將無線技術納 入其產品的原因 [6]。這是個「先有雞還是先有蛋」的問題：驅使
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