WELCOME MESSAGE AWARDS
HKU’s research has continued to grow in recent years. Our researchers have an impressive track record in securing funding through competitive funding schemes, publishing their findings, and translating their research for the benefit of the local and global community. In 2023, Clarivate named 50 HKU scholars among the world’s most highly cited researchers and 167 in the world’s top 1% of scientists. Outstanding researchers from across the globe have joined HKU. HKU researchers are garnering recognition from prestigious academies, with our scholars holding more than 100 memberships of about 25 academies around the world as well as in Hong Kong and Mainland China.
Our researchers have also received a wide range of international, national and local honours and awards. Notable examples include the Porter Medal, the American Chemical Society National Award, State Natural Science Awards, Future Science Prizes, Excellent Young Scientist Fund awards and Changjiang Scholarships. In this magazine, our researchers will share with us their significant research accomplishments and subsequent societal impacts upon successful downstream translation of their newly developed technologies. I am excited about our future and incredibly proud of the dedication and perseverance our research community has shown and their positive contributions. I wish everyone another successful year for research, grant application and publications!
A project of HKU Urban Planning and Design Professor Anthony Yeh and HKU Real Estates and Construction Prof Frank Xue has been awarded the First Prize of the 2023 Survey and Mapping Science and Technology Award.
HKU Earth Sciences Prof Joseph Michalski wins Xplorer Prize 2023. He is the first non-Chinese recipient of Xplorer Prize.
RESEARCH GRANTS
RGC General Research Fund/Early Career Scheme 2023/24
Health and Medical Research Fund 2022/23
284 68
RGC Theme-based Research Scheme 2023/24
NSFC Excellent Young Scientist Fund (Hong Kong and Macau) 2023
NSFC Young Scientist Fund 2023
19 2 8 projects, HK$276.2M projects, HK$72.8M projects, RMB$5.7M projects HK$130.4M projects, RMB$16M
Prof Max Zuojun Shen Vice-President and Pro-Vice-Chancellor (Research)
HKU and the Beijing Institute of Collaborative Innovation (BICI) held a Plaque Unveiling Ceremony on May 23, 2023, to mark the establishment of the HKU Collaborative Innovative Center in Hong Kong.
(From left) Professor Alice Wong, Associate Vice-President (Research), Professor Max Shen, Vice-President and Pro-ViceChancellor (Research), Dr Duoxiang Wang, President of BICI, and Dr
(Global
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officiating the plaque unveiling ceremony of the HKU Collaborative Innovation Center.
Xinjian Zhou, Vice-President
Collaboration)
BICI,
‘FISHING’ EXPERIMENT YIELDS IMPORTANT DISCOVERY IN GENE EXPRESSION
「釣魚」實驗 在基因表現領域
取得突破發現
Professor Xiang David Li of the Department of Chemistry and his team have cracked a two decade-long problem by discovering how to read a cell component that is implicated in gene regulation and developmental defects or cancers. The discovery opens the path for developing new treatments, as well as deepening understanding of gene expression.
化學系的李祥教授與團隊發現了如何解讀一種細胞成分，這種成分與 基因調控和發育缺陷或癌症相關。他們的發現破解了一個長達二十年 的問題，為研發新療法以及加深對基因表現的理解開拓了新方向。
研究團隊成員包括：（左起）翟元樑博士、黃永瀚博士、鮑秀叢博士和李祥教授。
The component in question is a histone. Histones are “spools” that the long strands of DNA wrap around to fit into a cell, and each cell contains four pairs of histones. The histones are often modified by diverse types of chemical groups. These modifications (also called histone marks) are like master switches that control cell development by turning gene expression on or off . Enzymes “write” and ”erase”’ the histone marks, which are then “read” by certain proteins that translate the information into a biological function – for instance, whether the cell should develop into a skin, brain or blood cell, or carry out DNA repair.
Since the human genome was mapped 20 years ago, scientists have been capturing many readers of histone modifications by “hooking” them with a probe and fishing them out for examination. But some histone modifications have proven to be tricky prey. Their writers and erasers may be known, but their readers are not, and without that, it is impossible to fully understand their functions.
A major elusive histone modification has been H3K79me2, which is important for blood cell regeneration and linked to leukaemia. That is, it has been elusive until now.
Utilising the technology that his lab developed to capture proteins that read histone modifications, Professor Li has been able to construct probes containing H3K79me2 and identify its reader, the protein menin. The finding has excited the world of science, with Nature Chemical Biology hailing the “long-awaited identity of menin as an H3K79me reader, which may inspire similar types of approaches for identifying novel epigenetic readers.”
The importance is not only in the discovery itself, but also the approach taken by Professor Li. He went beyond traditional biochemical approaches – which use a small fragment of the histone protein to act as bait to attract readers – and instead focused on forming a chemical bond that could trap even weak interactions between readers and a modified histone.
“There are many issues that can prevent the efficient identification of readers. First, the modifications on histones are highly dynamic – some can exist for seconds, some for hours, some even for generations. Second, the modifications only exist in a small fraction of the total histone protein, so we have to find a signal against very high background
noise. And third, the interaction between the reader and the modified histone can be weak and transient,” he said.
H3K79me2’s reader, menin, was a particular challenge because unlike most histone modifications, which reside on the loose “tails” that hang like a thread from the spooled DNA, H3K79me2 resides on the spool itself. That made it harder to find the right lure to attract the reader. “As a result, we needed to make a bigger bait and a better hook,” Professor Li said.
He and his team spent five years designing a bait and hook that targeted the infrastructure within which histones are contained, called the nucleosome. They developed a synthetic nucleosome that was in effect the bait and had a strong hook that could both capture and release the reader protein for subsequent analysis. They then used light-
This kind of information will be useful in designing new drugs to treat cancers associated with H3K79me2 misregulation.
“In terms of what’s next, we know that menin can bind to many different proteins. Several of those are known to regulate gene transcription. One hypothesis is that menin is a mediator that recruits other binding proteins to carry out different functions at different locations in the genome. But we need further experiments to validate that,” Professor Li said.
“In any case, our finding has provided some missing pieces to the role of menin, which is already an important drug target for leukaemia. It also raises the possibility of other potential therapeutic targets for menin inhibitors.”
In any case, our fnding has provided some missing pieces to the role of menin, which is already an important drug target for leukaemia. It also raises the possibility of other potential therapeutic targets for menin inhibitors.
induced chemistry to trigger the formation of a tight bond between the synthetic nucleosome and any nearby readers. Fortunately, the only reader that attached was menin.
“Basically, we did this fishing game and the experiment was beautiful because only one protein stood out – we didn’t have to worry about validating many candidates,” Professor Li said.
The team also used cryo-electron microscopy to visualise how menin “reads” the H3K79me2 histone and confirmed the interaction between the two. And they showed that inhibiting the enzyme that made marks on the histone prevented interaction between menin and the nucleosome.
The research has impact beyond these findings, too, now that the science world has recognised the value of Professor Li’s approach of combining chemistry, biochemistry, and molecular biology to advance understanding of the fundamental biological processes involved in gene regulation.
“Our technology is applicable to different modifications and different sites, so it is generally robust. With this study, we have tackled high-hanging fruit because the reader of H3K79me2 has been a long-standing question for the field. We’ve been able to demonstrate that our platform works and it has convinced more people that this technology is indeed an advance,” he said.
A chemical approach called “CLASPI”, developed by Prof. Li, was used in this study.
研究採用了李教授研發的「CLASPI」化學方法。
The research team members include: (from left) Dr Yuanliang ZHAI, Dr Jason Wing Hon WONG, Dr Xiucong BAO and Professor Xiang David LI.
X. David Li’s Group – Laboratory of Chemical Epigenetic: Posttranslational modifications (PTMs) of proteins are involved in the regulation of essentially every cellular process. The Li group is interested in studying regulatory mechanisms and cellular functions of PTMs by combining state-of-the-art chemistry, biochemistry, biophysics and cell biology approaches.
李祥教授研究小組–
化學表觀遺傳學實驗室：蛋白質的轉譯後修飾（PTM）幾乎與所有細胞過程的調節息息相關。李教授團隊通過結 合最先進的化學、生物化學、生物物理學和細胞生物學方法來鑽研 PTM 的調節機制和細胞功能。
上所說的成分就是組蛋白，即細胞裡DNA長鏈繞成的 「線軸」。每個細胞含有四對組蛋白，它們通常會因為 不同類型的化學基團而出現改變。這些改變（也稱組 蛋白標記）有著主開關一樣的作用，能打開或關閉基因表現來 控制細胞發育。組蛋白標記會由酶「寫入」和「刪除」，也會被 某些蛋白質「讀取」，再把資訊轉化為各種生物功能，例如細 胞是否應該發育成皮膚、大腦或血細胞，又或進行DNA修復。
自從20年前科學家繪製了人類基因組圖譜以來，他們便一直 像釣魚一樣，以探針的方法「鉤出」讀取組蛋白的蛋白質進行 觀察。研究發現部份組蛋白改變難以捕捉，雖然已知道哪種酶 負責「寫入」和「刪除」，但卻仍未能找出「讀取器」，而缺少 了這部分資料，便無法了解其功能。
香港大學的化學生物學家破解了一種組織蛋白標記，這種標記在癌症出現問題的基因調控程序中非常重要。
H3K79me2是其中一種至今仍然難以捕捉但會改變組蛋白的物 質，它對血細胞再生非常重要，並與白血病相關。
李教授的實驗室開發了一種技術，能捕捉讀取改變組蛋白的蛋 白質，並以這種技術構建含有H3K79me2的探針和識別其讀 取器：一種名叫menin的蛋白質。這項發現令科學界非常雀躍， 獲《Nature Chemical Biology》期刊表揚，指出：「menin作為 H3K79me讀取器是期待已久的發現，有望啟發其他識別新型 表觀遺傳讀取器的方法」。
除了發現本身，李教授所採取的方法同樣意義重大。傳統的生 化方法會以一小塊組蛋白誘餌讀取器，但李教授卻突破了這種 方法，而是專注形成一種化學鍵，以其捕捉多種讀取器與被改 變組蛋白之間的微弱互動。
間的互動。這種資訊將有助設計治療與H3K79me2錯誤調節 相關的癌症新藥。
李教授補充：「至於下一步，我們知道menin可以與許多不同 的蛋白質結合，而且已知道有幾種蛋白質能調節基因轉錄。我 們有一項假設，是menin是一種介質，能招募其他結合蛋白以 在基因組的不同位置執行不同功能。但我們需要再進行更多實 驗來驗證這一點。」
「無論如何，menin既然已是白血病的重要藥物靶標，我們的 發現為其作用解開了一些謎團，還提高了menin抑製劑成為其 他潛在藥物靶點的可能性。」
李教授這項研究還有其他重大影響，因為科學界已經認識到這 種結合化學、生物化學和分子生物學的方法別具價值，能加深 人們了解基因調控所涉及的基本生物學過程。
無論如何，menin既然已是白血病的重要藥物靶標，
我們的發現為其作用解開了一些謎團，還提高了 menin抑製劑成為其他潛在藥物靶點的可能性。
李教授說：「要有效識別讀取器，便先要解決很多細節。首先，組 蛋白改變是千變萬化的，有些可以只存在數秒，有些數小時，有 些甚至可以存在幾代。其次，組蛋白改變僅存在於組蛋白總體的 一小部分中，因此我們需要在很強的背景雜訊中找出信號。第三， 讀取器與被改變組蛋白之間的互動也可能非常微弱和短暫。」
H3K79me2的讀取器menin是一項重大挑戰，因為與大多數組 蛋白改變不同，H3K79me2並不是位於由DNA線軸連住的鬆 散「尾巴」，而是在線軸之上，要找到能吸引讀取器的適用誘 餌變得難上加難。李教授說：「因此，我們需要製作更大的誘 餌和更好的鉤子。」
李教授和團隊花了5年時間設計出一種誘餌和鉤子，針對組蛋 白所在的核小體。他們開發了一種合成核小體，可以擔任具備 強力鉤子的誘餌，用以捕捉和釋放讀取器蛋白以進行後續分析。
然後，他們以光誘導化學作用來觸發合成核小體與附近任何讀 取器形成緊密結合。幸運的是，menin是唯一連上的讀取器。
李教授表示：「基本上，這個釣魚實驗成果非常美滿，因為只有 一種蛋白質脫穎而出，省卻了我們驗證許多候選者的工作。」
該團隊還使用冷凍電子顯微鏡來呈現menin「讀取」 H3K79me2組蛋白的過程，並確認兩者之間的互動。他們展示 出抑制在組蛋白上留下標記的酶可以防止menin和核小體之
他說：「這是一項整體穩健的技術，適用於不同的改變和區域。 H3K79me2讀取器是持續已久的難題，我們的研究為它克服了 一些高難度挑戰，證明我們的平台是有效的，也讓更多人相信 這項技術確實是一大進步。」
李教授和翟博士的合作，揭示了一種低溫電子顯微鏡結構， 一種稱為H3K79me2-menin的蛋白複合物。
HKU Chemical Biologists decode a histone mark important for gene regulation program that go awry in cancer.
The collaboration between Prof. Li and Dr. Zhai unravels the cryo-EM structure or the H3K79me2menin protein complex.
BRINGING CARMAKERS UP TO SPEED
推動汽車製造商 在發展上馳騁
When it comes to car crash tests, most people think of dummies being flung around or saved by seatbelts or airbags. But there is another critical factor in passenger safety: the vehicle itself. Important research by Professor Huang Mingxin has found that engineers and car designers may be overestimating the safety of new automotive metals, especially at high speeds. He has also uncovered an explanation for why these steels may fail.
說起汽車碰撞測試，很多人會想到假人到處飛撞，又或被安全帶或安全 氣袋救回一命的場面。但乘客安全其實更關乎汽車本身。根據黃明欣 教授的重要研究發現，工程師和汽車設計師可能高估了新型汽車金屬 的安全性，尤其是在高速行駛時。他還找出此類鋼鐵失效的潛在成因。
Automakers and engineers have been developing new steels that are strong and lightweight and can thus reduce energy consumption. One researcher making headway is Professor Huang Mingxin, Chair Professor of Materials Technology, who has developed what he calls Super Steel, a super-strong, ductile (easy to form) and extremely tough material that is also cost-effective to make. However, his investigations have also led him to a discovery that is critical to everyone in both the car and steel industries: the safety tests commonly used for new steels are unlikely to give a true picture of the dangers of high-speed crashes in cars built with these metals.
In particular, he has found that the high performance of advanced steels – called quenching and partitioning (Q&P) steels – under low-speed conditions cannot be replicated at high speeds, upending conventional wisdom. Q&P steels have become popular because they are stronger and lighter than traditional steels and can still retain ductility.
“Usually, people evaluate the material properties of a metal in a lab only at a low speed. The so-called textbook thinking is that since the Q&P metal’s strength and ductility is increased at low speed, it should perform similarly well at a high speed. But we found this is not the case and the steel becomes softer at high speeds,” he said.
Using a special testing facility that has a camera capable of capturing five million frames per second, Professor Huang and his team were able to record the performance of new steel from very low to extremely high speeds (well over 100km/hour) and demonstrate the effect.
“We want to let engineers and designers know about this phenomenon so they can take this into consideration to protect passenger safety. Otherwise, they could overestimate the car’s safety performance in a crash,” he said.
Just why that happens was explained in a subsequent study that Professor Huang published this year. Like the earlier study, it started by looking at the TRIP effect, which stands for transformation-induced plasticity and is meant to keep Q&P steel strong and ductile. The TRIP effect is a process that transforms soft austenite crystals into harder martensite crystals and enables greater elongation of the steel, enhancing its strength and ductility.
The first study, published in 2020, showed that the TRIP effect weakens at high speeds. This year’s study, using a room temperature Q&P steel that Professor Huang’s team had developed, pinpointed the problem to carbon atoms and their interaction with the dislocations that take place
Figure 1. Microstructure of the Q&P steel before deformation. (a) SEM image of the etched sample, showing the martensite (α´) matrix and retained austenite (g). (b) Synchrotron X-ray diffraction (XRD) profile of the Q&P steel, showing the presence of α´ and g phases. (c) Electron backscatter diffraction (EBSD) phase map and (d) corresponding inverse pole figure (IPF) map. 圖1.Q&P鋼變形前的顯微結構。(a) 蝕刻樣本的掃描電子顯微鏡圖像，顯示馬氏體（α ）基質和殘餘奧氏體（g）。(b) Q&P鋼的同步 加速器X光繞射（XRD）剖面，顯示存在 α ´ 相和 g 相。(c) 電子背散射繞射（EBSD）相圖和 (d) 相應的反極圖（IPF）。
We want to let engineers and designers know about this phenomenon so they can take this into consideration to protect passenger safety.
with the TRIP effect – i.e., in the change from austenite to martensite crystals.
Carbon atoms move around and pin down any dislocations in the crystals when the metal is in motion so that the metal retains its strength. However, while this function works well when the metal is moving at low speeds, Professor Huang demonstrated that at high speeds, the carbon atoms cannot keep up with the dislocations. Although the TRIP effect still takes place, the carbon pinning effect is lost and the metal is weakened.
“Overall, this makes the materials softer. So, if you drove a car into a big pillar, the metal would deform and hurt the passengers because it cannot absorb the energy from the impact,” he said. “On the other hand, you also don’t want the metal to be too brittle because then it will just fracture.”
Fundamentally, this is a problem that comes down to the nature of carbon atoms in motion. “At this moment, we are not yet able to change their physics,” he said.
Nonetheless, carmakers can use the findings to make their vehicles safer by designing thicker components to absorb the energy of crashes – and of course, ensuring that they conduct testing at high speeds, he said.
Professor Huang’s own Super Steel is not exempt from the high-speed effect and he is working to improve the material. At the same time, he has been enhancing his testing facilities to test beyond automotive steels.
Recently, he and his team added a new component to their high-speed testing facilities, making it possible to also test at high temperatures of 1,200-1,500 degrees Celsius. Very few research facilities in the world have both capabilities. The team are testing high-temperature alloys used in airplanes to see if any abnormal results can be observed at both high speeds and high temperatures in these alloys, too.
The impact of this research adds to his other impactful work. Professor Huang also developed the world’s first anti-COVID-19 stainless steel. In all his research, he works closely with the steel and car industries in mainland China, Europe and the United States. “I expect to collaborate in future with the airline industry,” he added.
Professor Huang has received local, national and international recognition for his work. In 2022, he was awarded a Croucher Senior Research Fellowship, and received the HKU Outstanding Researcher Award 2022 and HKU Innovator Award 2022. He also received a silver medal at the Special Edition 2022 Inventions Geneva Evaluation Days for his anti-COVID-19 steel, and a gold medal in the 2021 Geneva event for Super Steel. In 2021 he was also awarded a 2021 Xplorer Prize, which goes to exceptional scientists under the age of 45 and is supported by Tencent.
Figure 2. (a) True stress-strain curves of interrupted tensile tests at 10-3 s -1 (dashed lines) and 600 s-1 (solid lines). (b) Synchrotron XRD profiles of interrupted samples with different plastic true strains at strain rate of at 10-3 s-1. (c) Synchrotron XRD profiles of interrupted samples with different plastic true strains at strain rate of 600 s-1. (d) Evolution of austenite volume fraction deformed at 10-3 s -1 (black squares) and 600 s -1 (red circles).
圖2. (a) 10-3 s-1（虛線）和600 s-1（實線）下斷續拉伸試驗的 真實應力-應變曲線。(b)塑性真實應變不同的中斷樣本同步 加速器XRD剖面，應變速率為10-3 s-1。(c) 塑性真實應變不同 的中斷樣本同步加速器XRD剖面，應變速率為600 s-1。(d) 在 10-3 s-1（黑色方塊）和600 s-1（紅色圓圈）變形的奧氏體體積 分數演變。
Professor Mingxin Huang 黃明欣教授
了降低汽車操作時的耗能，汽車製造商和工程師不斷 開發堅固輕便的新型鋼材。材料技術講座教授黃明欣 教授便是其中一位在此領域取得嬌人進展的研究人 員，他所開發的「超級鋼」是一種強度超高、富有易於成型的 延展性，而且非常堅韌的材料，在生產上具有成本效益。然而， 黃教授的調查發現到一般用於新鋼的安全測試，實際上不太可 能反映以此等金屬製造的汽車，在高速碰撞時的危險。這發現 對汽車業和鋼鐵業每一位從業員都至關重要。
其中最顛覆傳統智慧的發現，是先進鋼材（稱為淬火配分 鋼，簡稱Q&P鋼）在低速條件下的高性能無法在高速下複製。
Q&P鋼備受歡迎，是因為它們比傳統鋼材更堅固輕巧之餘，也 能保持延展性。
黃教授表示：「實驗室一般只以低速評估金屬的材料特性，根 據傳統的教科書思維，由於Q&P金屬的強度和延展性在低速 時增加，因此在高速下的表現也該不相伯仲。但我們發現情況 並非如此，鋼在高速下會變軟。」
黃教授和他的團隊透過特別的測試設施，以每秒能捕捉500 萬幀的相機紀錄新鋼材從非常低到極高速度的性能（最高速度 超過每小時100公里），並展示效果。
Figure 3. (a) Experimental setup of the high-speed digital image correlation (DIC) measurement. (b) Initially undeformed specimen with speckles on the surface. (c) High-speed DIC results of the Q&P steel at different true strains. The specimen was deformed at 600 s-1 圖3. (a) 高速數碼圖像相關測量的實驗裝置。(b) 最初未變形的樣本，表面有斑點。(c) Q&P鋼在不同真實應變下的高速數碼圖像相 關測量結果。樣本在600 s-1 時變形。
我們希望讓工程師和設計師瞭解這種現象，在保護
乘客安全方面能考慮到這一點，否則便有可能高估 汽車在碰撞中的安全表現。
他說：「我們希望讓工程師和設計師瞭解這種現象，在保護乘 客安全方面能考慮到這一點，否則便有可能高估汽車在碰撞中 的安全表現。」
黃教授今年發表了一項後續研究，說明發生這種情況的原 因。與此前的研究一樣，首先從TRIP效應說起。TRIP的全寫 transformation-induced plasticity，即相變誘導塑性，這種塑 性能保持Q&P鋼的強度和延展性。TRIP效應能把軟奧氏體晶 體轉化為較硬的馬氏體晶體，令鋼材有較大伸展，從而提高強 度和延展性。
Figure 4. Carbon distribution of the Q&P steel after deformation. (a) Atom probe tomography (APT) carbon atom map of martensite after fracture at strain rate of 10-3 s-1. (b) Carbon concentration profile taken from ROI 3 marked in (a). (c) APT carbon atom map of martensite after fracture at strain rate of 600 s-1. (d) Carbon concentration profile taken from ROI 4 marked in (c).
圖4. Q&P鋼變形後的碳分佈。(a)馬氏體斷裂後碳原子圖的原 子探針斷層掃描，應變速率為10-3 s-1。(b)取自(a)標記ROI 3 的碳濃度曲線。(c) 600 s-1 應變速率下馬氏體斷裂後的原子探 針斷層掃描（APT）碳原子圖。(d) 取自(c)標記ROI 4的碳濃 度曲線。
他說：「儘管如此，汽車製造商可以根據上述研究結果，設計 更厚的部件來吸收碰撞能量，使他們的車輛更安全，當然同時 也須確保以高速進行測試。」
黃教授本身研發的超級鋼也同樣受高速效應影響，所以也在努 力改進材料。與此同時，他也有提升測試設施，以便進行汽車 鋼材以外的測試。
黃教授和團隊最近在他們的高速測試設施中增加了新的部件， 令測試可於攝氏1,200-1,500度的高溫下進行。目前世界上同
2020年發表的首項研究發現TRIP效應在高速下減弱。本年 的研究中，黃教授團隊以自家開發的室溫Q&P鋼準確找出問 題成因，原來是因為碳原子及碳原子與TRIP效應的位錯相互 作用，即是由奧氏體變成馬氏體晶體的變化。
當金屬在移動時，碳原子四處移動並牽制晶體中的任何位錯， 從而保持金屬的強度。然而，雖然這種功能在金屬低速移動時 效果良好，但黃教授證明了碳原子在高速下無法追上位錯。雖
然TRIP效應仍然發生，但碳原子的牽制效應會消失，從而令 金屬被弱化。
黃教授說：「總括而言，效應令材料軟化。因此，如果你開車時 往大柱子撞過去，金屬便會因為無法吸收撞擊能量而變形，最 終傷害到乘客。另一方面，金屬也不能太脆，否側撞擊後便會 斷裂。」
黃教授補充：「基本上，這是一個碳原子運動時出現的性質問題。 我們現時還無法改變他們的物理學。」
時具備這兩種測試能力的研究機構數量非常少。團隊正在測試 飛機所使用的高溫合金，以觀察這些合金在高速和高溫下是會 否出現異常。
上述研究所帶來的影響，為黃教授其他研究工作錦上添花。他 還開發了全球首款可殺滅新冠病毒的不銹鋼。他的各項研究均 與中國內地、歐洲和美國的鋼鐵和汽車行業密切合作。他補充 說：「預期將來會與航空業合作。」
黃教授的工作成果備受本地、國家和國際認可。他於2022年 獲授「裘槎優秀科研者獎」，同年並獲頒「2022年香港大學傑 出研究員獎」及「2022年香港大學創新者獎」。黃教授還憑其 可殺滅新冠病毒的不銹鋼於 2022 年日內瓦國際發明展獲得銀 獎。在 2021 年日內瓦國際發明展中，黃教授的超級鋼材獲金 獎殊榮。他還於2021年獲得由騰訊支持的「2021年科學探索 獎」，成為該獎項所表揚的其中一位45歲以下傑出科學家。
BREAKING THE LIGHT BARRIER
突破 光波界限
How tightly can a wave of light be focused? Until the work of Professor of Mechanical Engineering Nicholas Xuanlai Fang and his collaborators, the common wisdom about the diffraction limit of light was about 200-400 nanometers; anything smaller and the light would blur. But Professor Fang proved that it was possible to break that limit. He managed to focus a ray of light to as tiny as 10-20 nanometers, opening the way for potential new applications related to energy, optical data storage, microscopy, and even sound (given that it travels in waves, just like light).
光波聚焦能有多緊密？傳統智慧普遍認為光的衍射極限約為200-400 納米，小於此數光線會變得模糊。然而，機械工程教授方絢萊和合作者 發表了相關研究，證明極限可以被突破，成功把光束聚焦至10-20納米。
這項發現將為與能源、光學數據儲存和顯微術相關的潛在新應用開拓更 多可能性，甚至連與光同樣以波浪傳播的聲音也可受惠。
方教授及其團隊成員於香港大學留影，拍攝於2023年12月 由左至右: 方絢萊教授、王斯佳博士、張萍萍女士、董爾謙博士、李永楠先生、鐘曉玲博士、屈思超博士、李禹辰博士和陸海鷗先生
The main thrust of my research started by looking at how to deliver light energy at ever-smaller dimensions and control it at high precision,” he said. “We wanted to push the understanding of how to confine light.”
Professor Fang, who recently came to HKU from the Massachusetts Institute of Technology, achieved his breakthrough by creating a thin layer of silver and applying ion beams and other state-of-the-art tools to that surface to concentrate different wavelengths of excitation. This created a tiny “footprint” of the light on the polymer that was smaller than the diffraction limit.
Experimenting with a range of gels, Professor Fang and his team identified some that could indeed change their presence under exposure to sunlight and the heat that it carries. The gels are invisible in water, but at elevated temperatures, they start to shrink and expel the water and become translucent, or have a jelly-like frosted appearance. This changes the optical property and thus the index of refraction.
The possible application of that is that it could reject heat coming through windows. Professor Fang and his team have indeed shown that containing the gel between plastic
The main thrust of my research started by looking at how to deliver light energy at ever-smaller dimensions and control it at high precision,”
The work was started while he was still at graduate school at the University of California, Los Angeles, and over nearly two decades since, he has managed to control light at eversmaller dimensions by exploring the interaction between light and different materials to enhance control and accuracy.
One of his recent successes has been in applying gel materials to manipulate light for energy-saving. This was inspired by the gel heat packs that people use to keep their hands warm in cold weather – Professor Fang noticed that when the packs are first opened, the gel is clear, but as heat is released, crystals form and it becomes opaque.
“This triggered me to think that this was an optical effect we could leverage by controlling the phase transition from liquid to a condensed material that rejects selected wavelengths of light,” he said.
sheets or embedding it in film can achieve this effect. Moreover, they have also been able to ensure the expelled water does not evaporate and instead can be reabsorbed into the gel when the light and heat intensity drop, thus reversing the opacity. In this way, heat can be blocked – or not – according to light exposure.
The work has involved collaboration with Professor Tony Feng Shien-Ping of City University who has been developing smart windows, which is one of the reasons Professor Fang came to Hong Kong, along with the general research opportunities here. They have shown that applying their film to windows could block out enough sunlight to reduce cooling costs by half in temperatures above 28 degrees Celsius. They are now looking for industry collaborators to do field studies.
“In Hong Kong, every square metre of window lets in something like 500 watts of heat. If we can reject that heat from the sun, depending on the room temperature conditions and ambient environment, we may be able to save energy,” Professor Fang said.
Apart from energy-saving, Professor Fang is also looking at how to break the diffraction limit with respect to optical fibres, which use light to send and receive data bits. The effectiveness of optical fibres in processing data has come under strain because of the demands from ever-increasing Internet use and the transmission of data-heavy items such as videos. Being able to transmit light at smaller dimensions over optical fibres could provide a solution.
“Every cord of optical fibre can only allow a certain number of digital channels, but the cable cannot change its size to accommodate the growth in demand. I think the problem boils down to the diffraction limit and how to send and receive light in a parallel and highly compact form.
A third application where Professor Fang sees potential for overcoming diffraction limits is noise control.
“To a large extent, the problem of sound control has a similar root to light control,” he said. “On the one hand, it is getting harder to design a compact and energy-efficient sound source, like a speaker on a cell phone. On the other hand, there is the problem of reducing environmental noise, which requires new coatings and management solutions to reduce noise emissions.”
To tackle the first problem, he is investigating ways to focus soundwaves over thinner wavelengths. To tackle noise control, he is looking at how to both reject sound from entering a space (for instance, roadside noise) and absorb sound within a space (for instance, from an air-conditioner or hair dryer). The latter is further along in development and involves developing materials that are triggered to absorb noise when it reaches certain acoustic levels. This is still a pilot project, but already has interest from industry.
The smart coating can change its appearance from invisible and transparent view to milky and translucent form as the ambient temperature increases to 31 centigrade. As a result, unprecedented solar transmittance modulation of 81.3% was achieved, which promise to save an annual power cost of cooling up to 26% percent.
當環境溫度升至攝氏31度時，智能塗層的外觀會出現變化，由無形和透明變成乳白色和半透明。這種轉變能實現達81.3%的太陽能透 射率調變，效果前所未有，而且有望每年節省高達26%的冷氣開支。
Research on beating the diffraction limit could one day address this problem in information processing,” he said.
He is now testing materials and their structural properties to find better alternatives for improving the sending and receiving of optical data. One promising material is graphene, which has a thickness of just one atomic layer of carbon, but he cautions that progress has mainly been made at the lab-scale and there are still many hurdles to overcome.
Whether his biggest impacts will be in energy-saving, data transmission or noise control, or all three, Professor Fang traces a line straight back to his days as a graduate student. “My work started with the insights I gained there, where I started to learn how to apply the concepts of physics to diverse applications,” he said.
Group photos of Prof Fang and his group members at HKU campus, dated December 2023
From left to right: Prof Nicholas Fang, Dr Sijia Wang, Ms Pingping Zhang, Dr Erqian Dong, Mr Yongnan Li, Dr Xiaoling Zhong, Dr Sichao Qu, Dr Yuchen Li and Mr Haiou Lu
方
教授表示：「我的研究旨在探討如何以更小呎吋傳遞 光能，同時以高精度把它控制，希望藉此擴闊人類 對駕馭光能的理解。」
方教授最近才加入香港大學，此前任職麻省理工學院。他利用 離子束和其他先進工具，在薄薄的銀層上集中激發不同波長， 從而讓光在聚合物上產生小於衍射極限的微小「足印」，實現 上述突破。
方教授和團隊為一系列凝膠進行實驗，發現當中確有部分在日 曬和吸熱後變得不一樣。凝膠在水中不著痕跡，但在高溫下會 開始收縮、排出水分和變成半透明或霜面果凍（啫喱）狀，光 學特性和折射率也因而出現變化。
這項發現或可應用於窗戶上，用來阻隔經窗戶進入室內的熱量。 方教授和他的團隊已經證明了在兩片塑膠之間加入凝膠，又或 把凝膠嵌進薄膜，都可以實現隔熱效果。這兩種做法還能夠確
Using advanced display technology in conjunction with photochemistry, fine 3D microstructures with features comparable to the size of red blood cells can be formed over wide area at high throughput. This promises many exciting research opportunities from sustainable energy to organs on a chip.
利用先進的顯示技術與光化學，可以在大面積上以高通量形成精細3D微結構，其特徵與紅血球細胞大小相若。這項結果有望帶來很多 令人雀躍的研究機會，能應用於可持續能源以至晶片上的器官。
這項研究始於方教授的加州大學洛杉磯分校研究生時代，此後 近二十年來他不斷探索光與不同材料之間的相互作用，務求提 高控制度和準確性，最終成功在更小面積上實現光控。
方教授的最新成就是以凝膠材料操縱光以達至節能效果。這 概念源自寒冷天氣時人們用來暖手的凝膠暖包。方教授注意到 第一次打開包裝時呈透明的凝膠，會隨著熱量釋放形成晶體， 再變得不透明。
他說：「這讓我想到當中能加以善用的光學效應，就是控制液 體的相變，令其成為可排除指定波長光的冷凝材料。」
保凝膠受熱時排出的水不會蒸發，而是在光和熱減退時再次被 凝膠吸收，繼而令凝膠恢復透明度，實現按照曝光程度來隔熱 或不隔熱的效果。
這項研究是方教授與城市大學馮憲平教授合作的項目。方教授 選擇落戶香港，除了因為這裡不乏一般研究機會，也與一直研 發智能窗戶的馮教授息息相關。兩位教授已經證明了將他們的 薄膜貼在窗戶上能有效阻擋陽光，把攝氏28度以上的冷氣開 支降低一半。他們現正尋求產研合作以進行實地研究。
方教授說：「香港每平方米的窗戶都能透進約500瓦熱量。如
果我們可以根據室溫狀況和大氣環境阻隔來自太陽的熱能，便 有可能節省不少能源。」
節能以外，方教授還在研究如何突破光纖的衍射極限。人們上 網越來越頻密，加上串流影片一類數據傳輸量大的應用相繼出 現，令光纖的處理數據效率備受壓力。既然光纖以光來發送和 接收數據，以較小呎吋讓光在光纖間傳輸，便可以成為其中一 種解決方案。
方教授說：「每根光纖線只可容納某個數量的數碼通道，但電 纜無法改變其本身的大小來滿足需求增長。歸根結柢，這問題
可以從衍射極限著手，配合平行而高度緊密的方式發送和接收 光來解決。到了將來，衝破衍射極限的研究將可解決這個資訊 處理問題。」
方教授現正測試多種材料和研究材料的結構特性，希望找到更 好的替代方案來改善光學數據的發送和接收。厚度只有一個碳 原子層的石墨烯是很有潛力的物質，但方教授指出，石墨烯現 時主要在實驗室規模上取得進展，尚待克服的障礙仍然不少。
Fang’s group draw inspiration from modern imaging instruments that break the diffraction limit. In the photo, a microscope with advanced illumination is under construction.
方教授團隊從打破衍射極限的現代成像儀器中獲得啟發。圖中 所示為正在建構、配備先進照明的顯微鏡。
方教授認為克服衍射極限潛力的第三個應用是控制噪音。
他說：「聲音控制的問題在很大程度上與光控的原理相近。其
中一個難度越來越高的問題，是設計小巧節能的音源，例如是 手機上的揚聲器。另一個問題是減輕環境噪音，這方面需要用 到新的塗層和管理解決方案，才能降低噪音聲浪。」
為解決第一個問題，方教授正在研究把聲波聚焦於較薄波長的 方法。至於噪音控制的問題，他則試圖從隔音（如阻止路邊噪 音進入室內）和吸音（如空調或風筒聲）著手。現時吸音的進 展較佳，研發中的物料有望在指定音量觸發下發揮吸收噪音的 作用。雖然項目是先導性質，但已引起業界關注。
方教授的研究將會對節能、數據傳輸或控制噪音有著重大影響。
他把這些成就歸功於自己的研究生時代：「當時研究院給了我 很多啟發，我是從那時開始學習善用物理學概念，發展出各式 各樣的應用。」
Using principles of light scattering with nanostructures, Fang group invented a smart coating that can reject heat radiated by the sun using specifically tailored particles of desired size by solution processing.
方教授研究團隊利用納米結構的光散射原理發明了一種智能塗層，可以通 過溶液處理利用特製大小的顆粒來抑制太陽輻射的熱量。
我的研究旨在探討如何以更小呎吋傳遞光能，同時 以高精度把它控制，希望藉此擴闊人類對駕馭光能 的理解。
NOW YOU SEE IT, NOW YOU DON’T: ADVANCES IN MANIPULATING LIGHT
若現若隱：光操控的新進展
Professor Zhang Shuang, Chair Professor of the Department of Physics, has done ground-breaking work creating materials that can bend light waves and manipulate their appearance under different environmental conditions in ways that go well beyond the possibilities of traditional optics.
物理系系主任張霜教授的開創性研究，產生一種遠遠超越傳統光學 可能性的材料，能把光波彎曲和在不同環境條件下操縱光的外觀。
Conceptual schematic for the water‐immersion programmable dynamic switch of multi‐fold meta‐display. Quad‐fold imaging channels are enabled from a single metasurface at the prior‐and post‐ immersion states, such as independent‐encoded near‐field nanoprint images of a butterfly and a crab and far‐field holographic images of an airplane and a ship.
概念原理圖：多倍元顯示的水浸式可編程 動態開關。單一元表面在入水前和入水後 兩種狀態下，促成了四重成像通道，例如 獨立編碼和近域納米列印的蝴蝶和螃蟹圖 像，以及遠域的飛機和輪船全息圖像。
I’m interested in developing metamaterials at the nanoscale that can control optical properties at the interface and extend the refractive index of light beyond the very limited range available in nature,
Some of his key contributions have been to the understanding of how “invisibility cloaks” could work (HKU’s President Xiang Zhang has also contributed in this area) and to the development of meta-lenses that will advance cameras, corrective lenses and microscopes. Most recently, he has shown how images embedded in a super-thin material that he created can be made visible underwater and invisible in air – work that could have useful application in encryption and provide more informational channels from the same material.
“I’m interested in developing metamaterials at the nanoscale that can control optical properties at the interface and extend the refractive index of light beyond the very limited range available in nature,” he said.
The refractive index measures how deeply light will bend at an interface, for instance when it passes through air, water, glass or diamond. A classic example of refraction is a fish underwater – when seen from the shore, the fish will appear closer to the surface than it actually is due to the refraction of light at the water surface.
Professor Zhang has created metamaterials that can focus light at much shorter wavelengths than previously possible and, most importantly, can bend light beyond the ranges that occur in nature – even to the extent of negative refraction. This dislodges the light waves so dramatically that the object appears to be far away from its actual location, for instance a fish hovering above the negative index medium. “This is something you would not have been able to even imagine before,” he said.
The invisibility “cloak” or shell becomes possible under these conditions. When light hits the material, it can be bent in such a way that it goes around the object and resumes its direction on the other side. The human eye would only be able to see what is behind the object and not the object itself.
Such metamaterials are quite bulky, though, and still very much experimental. Their limitations prompted Professor Zhang to pursue a more practical approach to manipulating light waves – by creating a two-dimensional surface that could be applied to other objects to achieve similar optical results.
Since 2012, he has been developing surfaces or coatings covered in many structures only a few hundred nanometers in size – too small to be visible under a conventional microscope. These nanostructures are made of gold or silver and each is oriented in specific ways to bend and focus the light even when the surface is flat. Consider that without the nanostructures, the light waves would travel in straight lines and never meet, unless the structure was curved, like the lenses of eyeglasses. Professor Zhang’s innovation achieves that with simply a super-thin coating.
The thinness of the surface means it is possible to create tiny but highly efficient lenses, an application that has since been pursued by other researchers who are in the process of commercialising this “meta-lens” for such uses as mobile phone cameras. The surface could also make it easier to control for conditions such as astigmatism.
Professor Zhang has also found other functions for the meta-surface by generating holographic images that can be projected at close range or in the distance without losing their integrity. In this case, the surface nanostructures are closely spaced so they can encode more information and use light more efficiently. The image remains steady when viewed from all angles, without any jump in the image unlike conventional holograms.
However, there is an important limitation in both these applications: holograms can only project a single image. This prompted Professor Zhang to explore the possibility of encoding multiple images on a single meta-surface that would change depending on the environmental trigger – in this case, water.
By controlling the geometry of each nanostructure, he created a meta-surface that reveals a butterfly when exposed to air and a crab when exposed to water – two images from the same surface. Colour can also be controlled by manipulating the metal nanostructures (interestingly, this is not a new idea; stained glass windows in churches are made of different-sized gold and silver particles that reflect different colours. The material means the colour does not fade from exposure to sunlight, unlike paints and dyes).
Moreover, Professor Zhang engineered the surface so it could project its images both at close range and in the distance. Altogether, the surface contained four images: one that was revealed at close range underwater, one in the far field underwater, one at close range in the air and one in the far field under air.
The advantage of generating multiple sets of images under different environments is that it opens the way for encryption, by containing information that is invisible unless immersed in water. “This is the rough idea. There is still work to be done but we have shown that water immersion can be used to generate different images,” he said.
The next step will be to try to create these effects with moving images, similar to animation. Professor Zhang believes this will require a different approach and he is working on a solution.
“To generate multiple images, like in animation, you would need to make individual pixels dynamically tuneable. That’s not possible now because you cannot differentiate the environment for each pixel – once the surface is in water, all the pixels are in water. Ultimately, one would like to have electric control because that would make it possible to manipulate each pixel individually,” he said.
Professor Zhang’s achievements saw him named to the Clarivate Analytics list of 2022 Highly Cited Researchers and have brought a host of other honours.
The optical response of meta‐pixels. a) Structural diagram of the meta‐pixels. b) Electric‐field intensity contours of the meta‐pixel at y‐z plane in different surrounding refractive indexes from air (n = 1) to water (n = 1.33) under the incident light with y‐polarization at 590 nm. The size parameter of the meta‐pixel is P = 500 nm, lx = 200 nm, and ly = 300 nm. c) The CIE 1931 plot for the experimentally calculated structural color palettes of 116 meta‐pixels at prior‐ and post‐ immersion states. d) Experimentally recorded color palettes of 116 meta‐pixels with different periods and geometrical parameters at prior‐ and post‐immersion states, respectively. e) Experimental reflection spectra of selected six meta‐pixels in prior‐ and post‐immersion conditions. The insets are their displayed colors under the bright‐field microscope.
元像素的光學反應。a) 元像素結構圖。b) 元像素在y-z平面 處的電場強度等值線，圖中顯示了不同的環境折射率，包括 由空氣(n = 1) 至水 (n = 1.33)，入射光的Y偏振為590 nm。 元像素的大小參數為 P = 500 nm、lx = 200 nm 和 ly = 300 nm。 c) CIE 1931 圖，用於在入水前和入水後兩種狀態下實
left to right: Mr Zemeng Lin, Dr Hsun-Chi Chan, Mr Kebo Zeng, Mr Zhu Yuan, Miss Wenwen Liu, Dr Li Zhang, Professor Wenjia Li, Dr Qiuchen Yan, Professor Shuang Zhang, Professor Cuicui Lu, Dr Oubo You, Dr Fuxin Guan and Dr Zhongfu Li 由左至右: 林澤萌先生、詹勳奇博士、曾可博先生、袁著先生、劉雯雯小姐、張莉博士、李汶佳教授、閆秋辰博士、張霜教授、 路翠翠教授、游歐波博士、管福鑫博士和李忠福博士
張
霜教授的主要貢獻包括了解實現「隱形斗篷」的原 理（香港大學校長張翔也為此領域作出貢獻），還有 研發有望推動相機、矯正鏡片和顯微鏡發展的元鏡 頭。最近，張教授以自家研發的超薄材料嵌入圖像，展示出水 下可見、但在空氣中會隱型的效果。這項研究可以應用於加密 用途，並讓同一物料提供更多信息管道。
Water‐immersion pixel‐programmable meta‐display to exhibit dynamic nanoprint image switch via water‐immersion tuning.
a) Schematic illustration of the fabrication process for pixel‐programmable metasurface pattern without lift‐off requirement.
b) Experimental setup to characterize the water‐immersion switchable nanoprint image based on the angle‐resolved microscope spectrometer (ARMS, Ideaoptics Inc). c) Scanning electron microscopic images (SEM) and the optical microscopic images at prior‐ and post‐ immersion conditions under 480 nm laser light. The selected four meta‐pixels can provide independent‐encoding reflection amplitude. The scale bars in SEM images are 500 nm. d) Target and experimental near‐field nanoprint images with reasonable image enhancement at prior‐ and post‐ immersion states. The nanoprint image could actively transform from a butterfly in the air state to a crab in the water‐immersion state. The scale bars correspond to 100 µm.
水浸式像素可編程元顯示器，通過水浸式調諧展示動態納米列印圖像 切換。a) 製造過程示意圖：無需剝離的像素可編程元表面圖案。b) 實 驗設定：以角度分辨顯微鏡光譜儀（ARMS，Ideaoptics Inc）為基礎 的水浸式可切換納米列印圖像。c) 480 nm激光照射下入水前及入水 後狀態的掃描電子顯微圖像（SEM）和光學顯微圖像。選出的四種元 像素能提供獨立編碼的反射幅度。SEM圖像中的比例尺為500 nm。d) 在入水前和入水後狀態下有合理圖像強化的目標和實驗近域納米列印 圖像。納米列印圖像可以主動從空氣狀態的蝴蝶轉變為入水狀態的螃 蟹。比例尺為100 μm。
他說：「我很有興趣開發納米級超材料，這些超材料可以在介 面控制光學特性，並將光的折射率延伸，超越自然界中非常有 限的範圍。」
折射率用來量度光穿過空氣、水、玻璃或鑽石時，在介面彎曲 的深度。在水下暢泳的魚就是折射的經典例子：從岸邊看時， 因為光在水面上折射，魚看起來比實際更靠近水面。
張教授所創造的超材料，可以將光聚焦在比以往短得多的波長 上，而最重要的是超材料可以把光彎曲，程度超出自然界中可 能出現的範圍，甚至實現負折射。在光波被極大移動下，令物 體看起來遠離實際位置，就好像魚兒在負指數介質上游泳一樣。
他說：「這是我們此前無法想像的。」
在上述條件下，隱形「斗篷」或外殼便成為事實了。光線照到 材料上時能被扭曲到繞過物體，再在另一側恢復走向。人類肉 眼只能看到物體後方而看不到物體本身。
不過，這種超材料相當笨重，而且仍屬實驗性質。針對這些局 限性，張教授努力尋找更實用的方法來操縱光波，就是創建可 以加在其他物體上的二維表層來實現類似的光學效果。
自2012年以來，張教授便一直研發覆蓋於不同結構上的表層 或塗層，這些表層面積僅有幾百納米，小得連用傳統顯微鏡也 無法看到。此類納米結構以金或銀製成，每個結構都以特定方 式定向，可以以平面形態把光線彎曲和聚焦。如果沒有此納米 結構，光波只會直線前行而且永遠不會相遇，除非結構像眼鏡 鏡片一樣彎曲。透過張教授的創新研究，只需要簡單的超薄塗 層便能實現屈光效果。
表層薄度令製造微小但高效的鏡片變成可能，而這正是其他研 究人員一直想辦法實現的商業化「元鏡頭」應用，能用於手機 相機等用途。表層還可以令散光等視力問題更容易受控制。
張教授還發現元表層的其他功能，就是生成可以在近距離或遠 處投射而不失真的全息圖像。在這種應用中，納米結構表層相 隔很近，可以為更多資訊編碼和更有效地用光。無論從任何角 度觀看，圖像都能保持穩定而不會像傳統全息圖般跳動。
但是，這兩種應用都面對一大限制，就是全息圖只能投射單個 圖像。這個限制促使張教授探討在單個元表層上為多圖像編碼 的可能性，而這個元表層還需根據環境觸發因素而產生變化。 水就是這裡所指的觸發因素。
張教授以控制每個納米結構幾何形狀的方法創出一種元表層， 在空氣中能現出蝴蝶，在水中則顯出螃蟹，實現了在同一表面 上呈現兩組圖像。操縱金屬納米結構還可用來控制顏色。有趣 的是這並非新想法：教堂的彩色玻璃窗便是以大小不同的金和 銀粒子製成，所以能反射不同顏色，而這種材料可以防止顏色 像油漆和染料那樣，因為日曬而褪色。
此外，張教授的精心設計令表層能在近距離和遠處投射圖像。
總的來說，表層包含四組圖像，分別可於水下近距離、水下遠域、 空氣中近距離和空氣中遠域的情況下顯示。
在不同環境下生成多組圖像，優點是能收納「入水能見、出水 不能現」的資訊，成為加密的新方法。他說：「這是粗略的想法， 仍有很多需要努力研究的地方，但我們已經證明了不同的圖像 可以透過浸入水中生成。」
張教授的下一步工作，是嘗試在移動圖像（類似動畫）創建這 些效果。他認為新嘗試需要採用不同的方法，而他正找出可行 方法。
他說：「要像動畫般生成多個圖像，你需要使獨立像素動態可調。 由於現時仍未能區分每個像素的環境，即表層進了水中，所有 像素都在水中，所以現時未能成事。理想的情況是最終能以電 作為控制，這樣便可以獨立操縱每個像素。」
張教授成就眾多、屢獲殊榮，包括入選科睿唯安（Clarivate Analytics）的2022年度全球高被引科學家。
我很有興趣開發納米級超材料，這些超材料可以在 介面控制光學特性，並將光的折射率延伸，超越 自然界中非常有限的範圍。
Optimization flow chart and experimental characterization of the switchable multi‐field meta‐display via water‐immersion tuning. a) Flow chart of the iterative calculation process for optimizing the water‐immersion programmable quad‐fold meta‐display by the modified simulated annealing algorithm (SAA). b) Local diagram of the optimized structural arrangement and the corresponding SEM image of the fabricated sample. The scale bar is 4 µm. c) Experimental setup to characterize the water‐immersion switchable meta‐holographic images. d) Schematic for water‐immersion capsule for tuning the immersion‐state. e) Simulated and measured water‐immersion independent‐encoded multi‐field meta‐images. The meta‐display is switched between the independent‐encoded dual‐nanoprint and dual‐holographic images by actively immersion tuning between air and water states. The reconstructed holographic images exhibit the respective designated area and are reasonably processed with brightness/contrast enhancement. The scale bars in nanoprint and holographic images correspond to 100 µm and 1 cm, respectively.
通過水浸式調諧對可切換多域元顯示器的優化流程圖和實驗特徵。a) 流程圖：以模擬退火演算法（SAA）優化水浸式可編程四倍元顯示的 反覆計算過程。b) 優化結構配置的局部圖和製備樣本的相應SEM圖 像。比例尺為4 μm。 c) 展示水浸式可切換元全息圖像特徵的實驗裝 置。 d) 用於調節入水狀態的水浸式膠囊示意圖。 e) 模擬和量度的水 浸式獨立編碼多域元圖像。元顯示器通過在空氣和水狀態之間的主動 浸入式調諧，在獨立編碼的雙納米列印和雙全息圖像之間切換。重建 的全息圖像呈現出各自的指定區域，並經過合理的亮度／對比度增強 處理。納米列印和全息圖像中的比例尺分別為100
From
MIMICKING ‘LIFE’S TRANSISTORS’: Scientists create atomic-scale ion channel
模仿「生命的晶體管」： 科學家創造原子尺度的 離子通道
Ion channels play a key role in the cells of nearly all living organisms. They are gateways that facilitate the entry and exit of ions at an astonishing rate of millions per second. These channels possess the remarkable ability to selectively control the flow of different ions through neuron cell membranes, earning their nickname “life’s transistors.”
離子通道在幾乎所有生物體的細胞中都發揮著重要作用。這種閘道能 讓離子以每秒數百萬夥的驚人速度進出，而且擁有非凡能力，能選擇性 地控制不同離子通過神經元細胞膜，因此被稱為「生命晶體管」。
Ion channels use a fraction of the energy that a semiconductor transistor uses to regulate the flow of electric currents. They enable our brains to consume only about 20-24 watts of energy to perform their computing at speed, whereas a supercomputer requires as much as 30 megawatts to perform comparable times of calculation.
Imagine, then, if artificial ion channels could be engineered for the transfer and computing of information.
will significantly impact important applications such as seawater desalination and medical dialysis,” Professor Zhang said.
The team involved in the discovery, which included members from both HKU and the University of California, Berkeley, applied understanding from both physics and engineering to develop their device.
The ion transistor consists of a two-dimensional electricallygated graphene channel to transport potassium ions, which are positively charged. Negative charges were placed inside the graphene channel to attract the ions. The tiny dimension of the graphene channel, which consists of a single flake of reduced graphene oxide, was intended to force the ions to move quickly in a concerted manner.
One obstacle they had to overcome was that the potassium ions have a hydrated shell that makes them too large for the channel. To circumvent that, the team added an electrical voltage gate at the graphene channel to dehydrate the ions and pack them at a high density in the channel.
Shortening the distance between those positively charged ions promotes their Coulomb repulsion interaction. The effect is similar to the elastic collisions of metal balls in a Newton’s cradle, a small structure from which five or more metal balls are hung in a row. When a ball at one end is lifted and released, it collides with the next ball and the energy is very rapidly transferred through to the ball at the end, forcing it upwards. Here the repelling interaction between the positively charged ions was leveraged to push each other rapidly through the graphene channel.
This artificial ion transistor deepens our fundamental understanding of ion transport at the ultrasmall limit and will signifcantly impact important applications such as seawater desalination and medical dialysis,
That possibility has motivated ground-breaking research by HKU’s President, Professor Xiang Zhang, who with his team has shown, for the first time, that it is possible to manufacture atomic-scale ion channels that mimic the regulatory behaviours of biological ion channels and serve as ion transistors.
They developed an atomic-scale ion transistor with a channel height of only 0.3 nanometres, showcasing ultrafast and selective ion transport in a controlled manner.
“This artificial ion transistor deepens our fundamental understanding of ion transport at the ultrasmall limit and
“If the concentration of ions is higher, the mobility will be higher and the faster they will transport through the channel, in accordance with the Newton’s cradle mechanism,” said Dr Yahui Xue, first author of the paper and a former postdoctoral fellow of Professor Zhang who is now a professor at the Southern University of Science and Technology (SUSTech) in Shenzhen. “Our experiment shows that if we apply higher voltage, the concentration of ions will be much higher.”
The demonstrated dehydration and regulation of potassium ions are observable in biological potassium channels, which also leverage electrostatic interaction to reduce the
hydration diameters of potassium ions and enable them to enter the gated channel.
Integrating atomic-scale ion transistors into large-scale networks could potentially lead to artificial neural systems and even brain-like computers.
“If we can realise a one-dimensional channel, we can make use of it for computation and other information transmission applications. I won’t say this would replace electronic systems, but it would provide another option,” Dr Xue said. “In any case, we start with the unit, which we have done in this work. It is the foundation.”
The discovery could also lead to more energy-efficient transmission of signals in various applications. To progress to that goal, the team is working to shorten the artificial ion channels to further improve their energy efficiency while exploring ion channels that are suitable for different kinds of ions. Emulating the life system, the team is also working on a new ion channel architecture that allows the effective integration of compact ion channel networks.
The breakthrough was reported in Science in 2021 and also involved Dr Yang Xia, Dr Sui Yang, Dr Yousif Alsaid, Dr King Yan Fong and Dr Yuan Wang, who were all members of the Nanoscale Science and Engineering Centre at UC-Berkeley at that time.
圖1：由大小僅有3埃的石墨烯溝道製成的原子尺度離子晶體管的示意圖 圖2：離子滲透的開和關狀態的示意圖
of “ON” and “OFF” states of ion
Professor Xiang Zhang 張翔教授
Figure 1: Schematics of the atomic-scale ion transistor made of graphene channels of 3 angstrom size
Figure 2: Schematics
permeation
對於半導體晶體管用來調節電流的能源，離子通道 的耗能只是一小部分。離子通道讓人類大腦能夠在 僅消耗約 20-24 瓦的能量便能迅速執行運算，超級
電腦要達到類似的計算效能，需要多達 30 兆瓦的能量。
試想像，假如能夠設計人工離子通道用來傳輸和計算資訊，情 況將會如何？
這種可能性激發了港大校長張翔教授進行突破性研究，他與研 究團隊首次證明，製造可以模仿生物離子通道調節行為的原子 尺度離子通道，並用作離子晶體管是可行的。
他們開發了一種高度僅有0.3納米的原子尺度離子晶體管，展 示出能以控制自如的方式實現極速和具選擇性的離子傳輸。
張教授表示：「這種人造離子晶體管加深了我們對於離子在極 小空間內傳輸機理的理解，對海水淡化、醫學透析等一些重要 領域的應用，意義重大。」
參與是項發現的團隊分別來自香港大學和加州大學柏克萊分 校，他們運用物理學和工程學的理解來研發上述設備。
離子晶體管由一個二維電門控石墨烯通道組成，用來傳輸帶正 電的鉀離子。在石墨烯通道內加入負電荷便能吸引離子。石墨 烯通道的微小尺寸由單一還原氧化石墨烯薄片組成，作用是迫 使離子產生協同效應和快速移動。
團隊需要克服的一大障礙是鉀離子擁有水合外殼，對於離子通 道來說體積過大。為了避免這種情況，研究團隊在石墨烯通道 上加設了一道電壓門來為離子脫水，再在通道中把離子擠壓成 高密度。
Figure 3: Molecular structure of biological potassium ion channels with angstrom-scale selective filter 圖3：當使用埃納尺度的選擇性過濾器時，所呈現的生物鉀離子通道的的分子結構 (a) (b) potassium or water oxygen
這種人造離子晶體管加深了我們對於離子在極小 空間內傳輸機理的理解，對海水淡化、醫學透析等 一些重要領域的應用，意義重大。
縮短帶正電離子之間的距離會能加快它們的庫侖排斥相互作 用，效果就如在牛頓搖籃中金屬球的彈性碰撞。牛頓搖籃是一 個小裝置，把5個或以上金屬球用吊繩固定連排。只要抬起和 釋放其中一端的金屬球，它便會與下一個金屬球碰撞，能量會 飛快地傳遞到末端的球上，迫使它向上移動。研究團隊利用了 正電離子之間的排斥相互作用來快速推動彼此通過石墨烯通 道。
薛亞輝博士是研究的第一作者，也是張翔的前博士後研究員， 現任深圳南方科技大學教授。他解釋說：「正如牛頓搖籃機制 一樣，離子的濃度越高，動能移動也會越高，通過通道的速度 也會越快。我們的實驗顯示如果我們施加更高電壓，離子的濃 度便會大增。」
生物鉀通道中，還可以觀察到鉀離子的脫水和調節；生物鉀通 道還利用靜電相互作用來減小鉀離子的水合直徑，讓它們得以 進入門控通道。
以原子尺度離子晶體管結合成大規模網絡令人工神經系統，甚 至是類人腦的電腦有可能出現。
薛博士說：「如果能夠實現一維通道，就可以將其用於計算和 其他資訊傳輸應用。我不會說這將取代電子系統，但它將提供 另一種選擇。無論如何，我們這項工作以單位作為開始，形成 了其他研發的基礎。」
此項發現還可以令各種應用中的信號傳輸更加省電。為實現這 項目標，團隊正在努力縮短人工離子通道，希望進一步提升能 源效益，團隊也探索適用於不同種類離子的離子通道。團隊以 仿生系統為基礎，正在研究新型離子通道架構，藉以有效整合 成更精簡的離子通道網絡。
這項突破已於2021年在《Science》上發表，參與的研究人員 當時均來自加州大學伯克萊分校納米科學與工程中心，包括夏 洋博士、Sui Yang博士、Yousif Alsaid博士、方敬恩博士和 Yuan Wang博士。
ALGAE AND THE RED LIGHT-GREEN LIGHT GAME
藻類的 紅綠燈遊戲
Prof Xiaobo Yin and his co-workers propose an efficient photonmanaging strategy for optimizing solar spectrum distribution in photobioreactors, augmenting signifcantly and biomass production. This work paves a feasible and cost-effective way to promote the solar energy-to-biomass conversion process of microalgae by effciently utilising solar energy.
尹曉波教授及其同事提出了一套有效的光子管理策略，用於優化光生 物反應器中的太陽光譜分佈，顯著加強了藻類的光合作用和生物質量 產生。這項研究善用了太陽能，以具成本效益的可行方法來促進微藻 把太陽能轉化為生物質量的過程。
Professor Xiaobo Yin has developed a material that improves the quality of sunlight reaching algae, enabling it to potentially produce more and higherquality biomass that could, in turn, be used as ingredients in high-quality medicines and other bioproducts.
Algae has great promise for environmental benefits. Just one pound of dry algae can consume nearly two pounds of carbon dioxide (CO2), making it a candidate for addressing climate change. More importantly, the algal biomass has been regarded as not only a feedstock for the sustainable production of a range of value-added compounds including medicines, cosmetics and protein substitutes, but also a promising substrate for biofuel generation.
But within those potentials are a number of challenges, the foremost being how to augment algae’s photosynthesis and produce the algal biomass on a large scale. Professor Xiaobo Yin, Global STEM Professor of Mechanical Engineering and Professor of Physics at HKU, has been investigating this with his team. Their starting point is a desire to learn from nature.
Rather than genetically modify algae or try other tinkering, as others have done with limited success, they are working with algae in its natural state and trying to improve its major input – sunlight – to better its photosynthesis.
“What we are doing is keeping the algae as is and controlling the quality of light it receives to promote its growth. It’s a physically passive approach but we’ve been able to demonstrate that photon [light particle] management can be used to promote the conversion of solar energy to biomass by algae and other photosynthetic compounds,” he said.
The concept of this approach is seemingly simple, being based on the colour of light rays reaching the algae. Green light is a major component of sunlight, but photosynthetic compounds do not really interact with it – the green is mostly rejected which is how green objects get their colour. Red light, on the other hand, is highly effective in the photosynthesis process. So Professor Yin decided to turn the majority of green light into red light.
“The idea is to create a material that converts green light to another colour, and as long as you set the condition right, in principle, the algae could grow better. We have tried to make that hypothesis a reality by using spectrum-converting materials,” he said.
He and his team developed a micro-structured photonic film for sunlight management in a two-step process. One step is to efficiently convert the main green photons into red ones. Their micro-photonic film can convert 90 per cent of the green photons it captures into red photons.
The second step is to get those red photons to travel in mostly one direction, which is downwards to the algae.
“Typically, for a piece of glass or plastic material, merely 20 per cent of the converted photons can emerge out of the material and even then, half of the photons go downwards and half go upwards – so in fact, less than 10 per cent of the light can be utilised for effective photosynthesis. Efficient light extraction and more than that, one-way light extraction structures that deliver all possible light to the photosynthesis organism, are the must-have,” he said.
The film achieves a combined efficiency rate of 50 per cent, meaning the algae are receiving that much more useable
light. “If you had, let’s say, 100 green photons, they literally would not work with the photosynthesis process. Now you are getting 50 additional red photons from those green ones that have been converted to red and can get involved in photosynthesis. It’s a very simple game,” he said.
Moreover, the micro-photonic film is easy to fabricate. The team tested it in both laboratory-scale and scaled-up outdoor photobioreactors. “The film efficiently improves the overall spectral quality of the sunlight reaching the microalgae in the photobioreactors. This increases the conversion efficiency of solar energy to chemical energy and leads to a tremendous augmentation in biomass productivity,” he said.
The team is now investigating how to improve the performance of their film. The indoor experiments performed better than the outdoor ones because it was easier to control all the parameters, so now they are trying to achieve comparable results in both. They are also trying to better understand the process of improving algae growth at a relatively large scale so they can produce higher quality
biomass, which would be a more viable product in financial terms in the short and medium term.
“A lot of people want to utilise algae production for larger scale applications, such as fuel, but the cost-effectiveness and scalability are important problems. With high-quality algae, maybe you can build a better financial model and gradually scale things up,” he said.
“We are focusing on more precise control of the conditions at high density. Eventually, if you can scale up further and drive the cost down, you can expand your portfolio to lower value but large volume biomass utilisation, like biofuel.” A larger scale would also have the secondary benefit of absorbing more carbon dioxide.
Professor Yin was named one of the world’s most Highly Cited Researchers in 2022 by Clarivate Analytics, in the field of physics. He was also a recipient of the Xplorer Prize 2022, which is one of the most generous talent funding programmes for young scientists in China.
We are focusing on more precise control of the conditions at high density. Eventually, if you can scale up further and drive the cost down, you can expand your portfolio to lower value but large volume biomass utilisation, like biofuel.
Professor Xiaobo Yin 尹曉波教授
曉波教授研發了一種材料，可以改善陽光照射到藻類 的品質，使藻類生產出更多更高品質的生物物質，能用 作優質藥物和其他生物製品的原料。
藻類潛質優厚，只需要一磅乾藻就可以消耗近兩磅二氧化碳， 可見藻類能產生龐大環境效益，是應對氣候變化的好選擇。更 重要的，是藻類生物物質不但能充當進料，用以持續生產藥物、
化妝品和蛋白質替代品等高增值化合物，更是生產生物燃料方 面別具潛力的基質。
然而在眾多潛力中還有不少挑戰，其中最首要的是增強藻類的 光合作用和大規模生產藻類生物物質。尹曉波教授是香港大學 機械工程教授和物理學教授，他與團隊正研究上述問題，他們 的出發點來自向大自然學習的渴求。
有別於其他人效果不彰的藻類基因改造或其他修補方法，團隊 的研究方向是嘗試從陽光入手，透過在自然狀態下改善藻類的 主要輸入來提升光合作用。
尹教授說：「我們正在做的是保持藻類原樣，並控制所接收陽 光的品質來促進生長，是一種物理上被動的方法。我們已經證 明了管理光子[光粒子]能促進藻類和其他光合作用化合物把 太陽能轉化為生物物質。」
這種方法的概念頗為簡單，就是以接觸藻類的光線顏色為基礎。
綠光是陽光的主要成分，但光合化合物並不會與綠光產生實質 相互作用––綠光大多被拒諸門外，所以綠色物件才會呈綠色。
另一方面，紅光在光合作用過程中非常有效。尹教授於是決定 把大部分綠光轉為紅光。
他說：「我們的想法是創造一種能把綠光轉化為另一種顏色的 材料，原理上只要條件設置正確，藻類便可以長得更好。我們 嘗試了使用能轉換光譜的材料令此假設成真。」
尹教授與團隊利用兩個步驟開發了一種用於陽光管理的微結構
光子薄膜。第一步是有效地把主要的綠色光子轉換為紅色光子。 這種微光子薄膜可以把收集到的九成綠色光子轉化為紅色光 子。
第二步是讓這些紅色光子大致沿同一方向前進，即往下向著藻 類走。
尹教授解釋說：「一塊玻璃或塑膠材料通常只有20%的轉換光 子可以穿過材料，這些光子中有一半向下游、一半往上走。所 以實際上僅有不到10%的光可用於有效的光合作用。因此，我 們必須找到高效（最好是單向）的光提取結構，令所有可以取 到的光都射向可進行光合作用的生物。」
我們專注於更精確地控制高密度下的狀態，最終如能
進一步擴大規模和降低成本，便可以把投資組合延伸 至如生物燃料這類價低量大的生物物質應用。
這塊薄膜實現了50%的綜合效率，意思是藻類可以比之前多 吸收可用光。尹教授說：「假設有100個綠色光子，它們實際 上不會在光合作用過程中發揮作用。現在，你從那100個綠色 光子中把50個轉為紅色，它們便可以加入光合作用。這是一 個非常簡單的遊戲。」
此外，這種微光子薄膜也易於生產。團隊已在實驗室規模和較
大規模的室外光生物反應器中對其進行了測試。尹教授說：「這 種薄膜能有效提高整體光品質，讓光生物反應器中的微藻可以 接觸到更多陽光，提升了太陽能轉化為化學能的效率，大大提 高生物物質的生產力。」
團隊現正研究如何提高薄膜的性能。由於室內實驗時更容易控 制所有參數，所以表現也較室外實驗好。團隊現正嘗試在兩者 中取得相若的結果，還努力深入瞭解在相對較大規模上改善
藻類生長的過程，以便生產出更高品質的生物物質，成為短期 和中期財務上更可行的產品。
他說：「很多人希望在燃料等更大規模的應用中採用藻類生產， 但成本效益和可擴展性都是重要問題。有了優質藻類，也許就 可以建立更好的財務模型，再逐步把規模擴大。」
「我們專注於更精確地控制高密度下的狀態，最終如能進一步 擴大規模和降低成本，便可以把投資組合延伸至如生物燃料這 類價低量大的生物物質應用。」規模更大的另一好處，是能吸 收更多二氧化碳。
尹教授入選科睿唯安（Clarivate Analytics）2022年度全球高 被引科學家。他也是2022年「科學探索獎」得主，該獎項是目 前中國國內金額最高的青年科技人才資助計劃之一。