Science Focus (issue 24)

Issue 024, 2023 SCIENCE FOCUS Thinking Out of the Box: Oral Insulin Pill 有何不可:口服胰島素藥丸 The World’s “Ugliest” Animals: The Blobfish Files 「醜陋」動物之最:水滴魚檔案 How Do Sticky Notes Work? 便利貼的原理是? Superellipse: Turning a Circle into a Square 超橢圓:介乎圓形與正方形的詩意 Pheromone Perfumes: Beyond Advertisements 費洛蒙香水: 廣告沒有告訴你的二三事

Dear Readers, Have you browsed our Instagram lately? We have re-visited some of our more popular articles in past issues and reproduced them in a short format. Hopefully, these recent posts would intrigue you to dive deeper into the original articles, which can be found on our website. In this issue, we continue our scientific journey across the ages. Do you know what is in common between the shape of a Swedish traffic roundabout and app icons? Do find out how they can be described mathematically in the article on superellipse. Another shape that has inspired scientists was that of a tortoise shell, which led to the design of an ingestible capsule for the injection of insulin inside the stomach. For those of you who use post-it notes often, have you ever wondered how their not-so-sticky glue was formulated? How did they get the iconic yellow color? We also explored the subject of attraction, based on visual and odor cues, which led us to consider pheromone perfumes and an oddly “cute” deep-sea fish. Finally, as you try to finish reading this issue in one go, with the help of a bowl of spicy ramen, pause before you fetch a glass of water to douse the fiery sensation in your mouth. By the time this issue reached you, we would have concluded our latest writing competition on Instagram. Please stay tuned for more interactive activities on our social media platforms in the near future! Yours faithfully, Prof. Ho Yi Mak Editor-in-Chief 親愛的讀者: 最近有沒有瀏覽《科言》Instagram 專頁?我們把以往一些受歡迎 的文章總結成篇幅較短的貼文,希望能勾起你閱讀原文的興趣,而原文 就在《科言》網頁,歡迎大家閱讀以了解更多。 這一期我們將繼續穿越年代展開科學旅程。你知道瑞典一個迴旋 處跟應用程式圖示在形狀上有甚麼共通點嗎?在介紹超橢圓的文章中 你可以找到在數學上描述它們的方法。另一個吸引科學家的形狀也許是 陸龜龜殼的形狀,它啟發科學家設計出一種可以把胰島素注射到胃部的 口服膠囊。經常使用便利貼的你可曾想過當中不太黏的膠水是怎樣發明 的嗎?便利貼又為何會選用它獨特的黃色呢?此外,我們亦會從視覺和 嗅覺探討「吸引」這回事,我們會介紹費洛蒙香水和一種樣子古怪得「可 愛」的深海魚。最後,如果你想在一口氣讀完《科言》前煮個辛辣麵,小 休一會,請緊記我們的忠告:不要嘗試喝水來撲滅口中灼熱的辛辣感! 這期《科言》送到你手之時,我們於 Instagram 舉辦的寫作比賽 應該已經步入尾聲。請繼續留意我們在不久將來於社交平台舉辦的更多 活動! 主編 麥晧怡教授 敬上 Message from the Editor-in-Chief 主編的話 Copyright © 2023 HKUST E-mail: Homepage: Scientific Advisors 科學顧問 Prof. Yukinori Hirano平野恭敬教授 Prof. Ivan Ip 葉智皓教授 Prof. Tim Leung 梁承裕教授 Prof. Kenward Vong 黃敬皓教授 Editor-in-Chief 主編輯 Prof. Ho Yi Mak麥晧怡教授 Managing Editor 總編輯 Daniel Lau 劉劭行 Student Editorial Board學生編委 Editors 編輯 Sonia Choy 蔡蒨珩 Peace Foo 胡適之 April Lam 林芷因 Roshni Printer Charlton Sullivan 蘇柏安 Helen Wong 王思齊 Social Media Editor 社交媒體編輯 Zoey Tsang 曾鈺榆 Graphic Designers 設計師 Ligeia Fu 付一乙 Sirinant Khunakornbodintr 吳譪恩 Tiffany Kwok 郭喬 Charley Lam 林曉薏 Evangeline Lei 雷雨晴 Coby Ngai 魏敏儀 Contents Science Focus Issue 024, 2023 What’s Happening in Hong Kong? 香港科技活動 Material Tales — The Life of Things 1 天生我「材」─ 材料科學與設計 Mars Calling 火星的呼喚 Science in History 昔日科學 The Mathematical Avengers: Nicolas Bourbaki 2 數學復仇者聯盟:Nicolas Bourbaki Science Today 今日科學 Thinking Out of the Box: Oral Insulin Pill 5 有何不可:口服胰島素藥丸 Amusing World of Science 趣味科學 The World’s “Ugliest” Animals: The Blobfish Files 8 「醜陋」動物之最:水滴魚檔案 Understand Spiciness: A Pain but Not a Taste 12 辣……其實是一種痛? How Do Sticky Notes Work? 15 便利貼的原理是? Superellipse: Turning a Circle into a Square 18 超橢圓:介乎圓形與正方形的詩意 Pheromone Perfumes: Beyond Advertisements 22 費洛蒙香水:廣告沒有告訴你的二三事

What’s Happening in Hong Kong? 香港科技活動 Fun in Summer Science Activities 夏日科學好節目 Any plans for this summer? Check out these activities! 計劃好這個夏天的好去處了嗎?不妨考慮以下活動! Material Tales — The Life of Things 天生我「材」─ 材料科學與設計 Mars Calling 火星的呼喚 From prehistoric stones and bronzes to the latest nanoproducts, the inventive use of materials have propelled technological advancements throughout the ages. This special exhibition at the Science Museum features a collection from the London Design Museum, alongside innovative locally developed materials and interactive exhibits. You will discover the fascinating connection between materials and human civilization, explore the transformation of materials into everyday products, and be reminded of the potential catastrophic consequences of over-consumption on natural resources. Now being dry and largely uninhabitable, evidence suggests that Mars was once full of water, and perhaps life. To prepare for possible human exploration, NASA has sent five rovers to record the red planet’s climate and geology over the decades. Ambitious space travel advocates like Elon Musk and Jeff Bezos are even exploring affordable ways to send travelers to Mars. Do you want to visit the large volcanoes and canyons there one day? Watch the show at the Space Museum to plan your (grandchildren’s) grad trip! Period: May 19, 2023 – October 18, 2023 Venue: Special Exhibition Hall, Hong Kong Science Museum P.S.: This introduction was generated by ChatGPT, and edited by DeepL Write and human editors. Time: 3:00 PM and 4:00 PM on May 14, 2023 (Sun) 4:30 PM and 5:30 PM on June 18, 2023 (Sun) Venue: Lecture Hall, Hong Kong Space Museum Admission fee: Free admission on a first-come, first-served basis 展期: 2023年5月19日至 2023年 10月18日 地點: 香港科學館特備展覽廳 備註:這篇介紹由 ChatGPT 生成,經 DeepL Write 和 人類編者潤飾,再由人類翻譯。 時間:2023年5月14日(日)下午三時至四時 2023年6月18日(日)下午四時半至五時半 地點: 香港太空館演講廳 入場費:免費入座,座位先到先得 由史前時期的石頭和青銅到今時今日的 奈米產品,人類一直都能透過善用材料推動科 技發展。這次科學館的專題展覽會同時展出 倫敦設計博物館的藏品、本地研發的嶄新材料 以及一些互動展品,讓大眾了解材料和人類 文明之間的密切關係,探索材料轉化成日用品 的過程,亦會提醒我們過度消耗自然資源可 能帶來的災難性後果。 雖然現在的火星既乾涸又不宜居住,但證 據顯示它曾經水源充足,而且可能是個孕育生命 的星球。為著未來人類可能探索火星的一天, 美國太空總署在過去數十年曾把五個探測器送 上火星,以記錄這個紅色星球的氣候和地質情 況。Elon Musk和Jeff Bezos這些雄心勃勃 的太空旅遊提倡者更積極尋求方法把旅客送上 火星。有天你會想親身觀賞火星上巨大的火山 和峽谷嗎?趕快到太空館欣賞這套紀錄片,然 後為你(孫兒)的畢業旅行作好準備吧! 1

By Sonia Choy 蔡蒨珩 Any Marvel fan – or even most people, really – will know the Avengers – six superheroes who teamed up to save the world. Mathematics, on the other hand, always has the image of being a rather solitary affair. We have written about a modern-day mathematical Polymath Project on the Twin Prime Conjecture in Issue 020, but these collaborations have been happening for a while – almost a whole century ago, in fact. Meet Nicolas Bourbaki. Assuming the name of a French general who fought in the FrancoGerman war (1870-1871), Nicolas Bourbaki, founded 1934-1935, was in fact a collection of mathematicians writing collectively. The name was chosen in jest (founders of the group had a distaste towards hierarchy), and humor is a running theme throughout the group. The group’s founders were all French [1] – although later incarnations involved mathematicians of other nationalities; they were admirers of the German mathematician David Hilbert, and the German school’s emphasis on precision and rigor of proofs, as opposed to the French school’s more handwavy approach based on intuition. The group’s membership would change throughout the ages – there was an agreement that the current members would be kept secret, although former members discuss their involvement with the group openly. This secrecy is to allow the mathematicians to write as a collective without any individual egos involved and no chance to claim copyright of any sort. Most m e m b e r s agreed to gradually drop out after they turn 50, letting the younger generation take over [2]. In their place, new members are recruited through invitation to their annual conference as “guinea pigs”, and are accepted into the group once all the mathematicians agree to let them join [3]. Bourbaki’s main work was a textbook series on mathematics, known as the Éléments de mathématique (Elements of Mathematics). Originally wanting to write a new textbook for differential calculus [1], the group eventually covered the major areas of mathematics – analysis, algebra and geometry, as well as including more modern areas of active research in later volumes. The group was drawn to abstraction rather than concrete illustration; most of the core six texts (those published before 1954) consist of theorems and proofs written out formally, with little diagrams or examples to illustrate the ideas. The group also wrote articles and hosted a lecture series known as Séminaire Bourbaki (Bourbaki Seminar) in Paris since 1948, adding up to over a thousand lectures as of today. One of Bourbaki’s main activities was its periodic conferences, usually held in a rural location, where its

References 參考資料: [1] Guedj, D. (1985). Nicholas Bourbaki, Collective Mathematician: An Interview with Claude Chevalley. Mathematical Intelligencer, 7(2), 18–22. doi:10.1007/ BF03024169 [2] Senechal, M. (1998). The Continuing Silence of Bourbaki: An Interview with Pierre Cartier, June 18, 1997. Mathematical Intelligencer, 20, 22–28. doi:10.1007/BF03024395 [3] Mashaal, M. (2006). Bourbaki: A Secret Society of Mathematicians (A. Pierrehumbert, Trans.). American Mathematical Society. [4] Borel, A. (1998). Twenty-Five Years with Nicolas Bourbaki, 1949– 1973. Notices of the American Mathematical Society, 45(3), 373–380. [5] Bourbaki, N. (2004). Theory of Sets. Heidelberg, Germany: Springer. [6] Miller, J. (n.d.). Earliest uses of symbols of set theory and logic. Retrieved from [7] Corry, L. (2009). Writing the Ultimate Mathematical Textbook: Nicolas Bourbaki's Éléments de mathématique. In E. Robson, & J. Stedall (Eds.). The Oxford Handbook of the History of Mathematics (pp. 565–587). Oxford, UK: Oxford University Press. [8] Aczel, A. D. (2006). The Artist and the Mathematician: The Story of Nicolas Bourbaki, the Genius Mathematician Who Never Existed. New York, NY: Thunder's Mouth Press. 3 members met to draft content on certain topics for the Elements. Members would then present those drafts in front of everyone, and the material must be agreed upon unanimously before it can be published under the Bourbaki moniker. As a result, many drafts took years to complete, but they were also guaranteed to be mathematically rigorous after being vetted by all of its members. At these conferences, there were also lively debates and often heated disagreements; Laurent Schwartz reported that André Weil once slapped Henri Cartan on the head with a draft [3]. But almost miraculously, peace was restored within ten minutes, and the group was able to stick together. The group’s very strong belief in the culture of collaboration and lively debate held them together; they would stay together despite personal differences on certain issues, which made Bourbaki able to change its views on certain issues such as which topics to write about, sometimes in a completely opposite direction [3, 4]. As Claude Chevalley discusses in an interview [1], “One never feels like he is talking to a wall when talking to Bourbaki.” Bourbaki was most active in the middle of the 20th century, during the 1940s and 50s; only one volume of the Elements has been published in the 21st century, on algebraic topology. Nevertheless, the group leaves a sizable legacy on present-day mathematics, especially on symbols used in set theory [5, 6]. The group also had an influence on French structuralism, which prioritizes the study of the relationships between structures before the study of the structures themselves; for example, cultures should be studied in the context of other cultures they exploited in becoming their present day state. Some also blame Bourbaki for the snobbery towards applied mathematicians in France ever since their foundation, as many see pure mathematics as more superior than applied mathematics. The group’s goal of making mathematics more formal and abstract has made French mathematics students and mathematicians prioritize pure mathematics over applied mathematics, as the former is often expressed in symbols and abstract arguments, while the latter is largely guided by more concrete explanations. Benoit Mandelbrot, a former member who was a geometer, even went as far as to emigrate to the United States in part to escape Bourbaki’s influence in France [3]; in interviews, he has stated that the group was very much against geometry since the field often relied on pictures and diagrams in explanations; the members also scorned against any other mathematicians who disagreed with them on this issue. There was also an air of superiority within the group, with some of the group’s members thinking that they were better than other mathematicians [1, 7]. However, it is undeniable that Bourbaki had a sizable influence on mathematicians, both French and further afield; the Elements remains an encyclopedia of sorts for a number of mathematicians, with certain volumes becoming the standard text for that area [3, 4, 8]. Furthermore, despite all the controversy, perhaps their culture of lively debate and collaboration is one we can all learn from – some of the best work can only be produced after an argument.

即使你不是 Marvel 粉絲,也會認識由六個超級英雄組 成,拯救世界的復仇者聯盟。數學和復仇者聯盟看似風馬牛 不相及,畢竟數學向來給人的印象都是閉門然後獨自奮鬥的 一回事,但我們在第二十期曾經寫過關於孿生質數猜想的現 代數學合作計劃 — 博學者計劃(Polymath Project),然 而這些合作其實並不是甚麼新鮮事,因為將近一個世紀前 就已經有類似的協作,那叫Nicolas Bourbaki。 Nicolas Bourbaki在1934至1935年成立,真實身分 為幾位一同寫作的數學家,筆名取自普法戰爭(1870-1871) 中的一位法國將領。選擇這個名字當然也是一個玩笑(當中 成員並不崇尚階級主義),這多少與組織裡總是充斥著幽默 空氣有關。組織最初的成員全都是法國人 [1],儘管後來的 成員包括來自其他國家的數學家,但無論甚麼國籍也好,他 們都是德國數學家David Hilbert的仰慕者,相對於當年法 國派數學家喜歡隨直覺寫出不太嚴謹的證明,他們更欣賞 德國派務求寫出精確和嚴格證明的作風。 Bourbaki 的班底會隨時間改變,成員們同意把現役成 員名單保密,但前成員還是可以公開討論以前在組織參與 過的事情。把成員名單保密是為了讓成員能以單一身份共 同寫作,避免因個別成員自尊心作祟而影響寫作,也能避免 成員因版權問題而作出無謂的爭執。大多數成員都同意在 50歲時淡出組織,讓年青一代繼承他們的工作 [2]。新成員 會以「天竺鼠」(guinea pigs)的身分被邀請到周年大會, 在所有成員同意下才能加入組織 [3]。 Bourbaki 的主要著作是名為《數學原本》(Éléments de mathématique)的教科書系列。成員起初希望寫一本 全新的微分教科書 [1],但最後除了涵蓋數學的三大範疇: 分析、代數和幾何外,在後來的卷數還包含了較現代的活 躍研究範圍。Bourbaki 崇尚抽象的表達多於實在的表述, 在1954 年前出版的六卷核心文獻中,大多都採取了只將 定理和證明列出的寫法,甚少以圖像或例子去說明定理的 內容。除了編撰教科書外,Bourbaki 也寫過不少論文,還 在 1948 年起於巴黎舉辦一系列名為「Bourbaki 研討會」 (Séminaire Bourbaki)的講座,至今已舉辦講座數目超 過1000場。 Bourbaki 其中一個主要活動是周年會議,成員通常會 約定於郊區某處草擬《數學原本》某主題的內容。眾人會在 其他成員面前報告自己撰寫的草稿,內容須經全體成員一 致同意才能以Bourbaki 的名義發表。基於這個嚴格的審 核過程,很多草稿需要許多年才能完成,但內容的嚴謹程度 卻毋容置疑。周年會議中發生過不少激烈的辯論,也多次出 現因意見不合而鬧得面紅耳赤的場面,Laurent Schwartz 指André Weil 曾用草稿當頭怒打Henri Cartan [3],但 最終這次混亂奇蹟地在十分鐘內得以平息,成員間終究能 和好如初。成員們都堅信合作和辯論的價值,縱然他們在某 些事情上的看法可能有分歧,但他們仍然會堅守在組織裡, 這使Bourbaki 能從善如流,對諸如寫作方向等問題上的 立場可以靈活轉變,有時甚至能完全改變 [3, 4]。正如成員 Claude Chevalley在一次訪問中提到 [1]:「跟Bourbaki 對話的時候,你從來不會有對牛彈琴的感覺。」 Bourbaki 最活躍的時期為二十世紀中期,尤其是 1940 和 50 年代。到了21世紀,Bourbaki 只出版過一卷主題是 代數拓撲的《數學原本》。儘管如此,Bourbaki 對現代數 學的影響不容忽視,尤其是集合論中所採用的符號 [5, 6]。 Bourbaki 也影響了主張研究事物前,應先研究事物之間關 係的法國結構主義(譬如研究文化時,應先從綜觀它們如何 受其他文化影響而演變成今天的形態)。 然而並非所有人都同意 Bourbaki 的觀點:有人指責他 們認為純數比應用數學高尚,因而從一開始就對法國應用 數學家諸多挑剔的態度。組織決意令數學變得更嚴謹和抽 象的宗旨實際上亦使法國的數學學生投向多數以符號和抽 象概念表示的純數,多於以實在論述表示的應用數學。由 於 Bourbaki 在法國極具影響力,作為幾何學家的前成員 Benoit Mandelbrot在某程度上亦為了避開Bourbaki 而移民到美國 [3]。他在訪問中曾經透露組織成員極之針 對幾何學,因為這個範疇往往要利用圖像來說明定理,組 織更會鄙視一切對這個立場有異議的數學家。另外組織成 員亦心存一種優越感,有些成員甚至認為自己勝過其他數 學家 [1, 7]。 儘管如此,Bourbaki 對法國,甚至全世界數學家的影 響毋容置疑,《數學原本》仍然是一些數學家的百科全書, 其中數卷甚至成為了某些範疇的標準參考書籍 [3, 4, 8]。 此外,即使組織引來不少爭議,他們鼓勵討論和合作的 文化也許是我們應該學習的精神,畢竟一些最好的作 品只能在爭辯下誕生。

Thinking Out of the Box Oral Insulin Pill 口服胰島素藥丸 有何不可: 5 By Helen Wong 王思齊 Imagine the following scenario: You are required to stab your abdomen with a needle up to four times a day and seven days a week. Wouldn’t this be a nightmare for you? This is exactly what happens to people with type I diabetes [1]. These patients need regular insulin injections as their bodies cannot produce enough insulin to effectively lower blood glucose levels. To liberate type I diabetes patients from the nightmare, scientists and doctors have been searching for reliable oral insulin delivery systems for decades. However, extreme pH, the presence of proteases and thick mucus layers along the gastrointestinal (GI) tract posed great challenges to such a quest. In 2019, researchers at the Massachusetts Institute of Technology reported a breakthrough study in which they designed a novel ingestible device called selforienting millimeter-scale applicator (SOMA) only at the size of a blueberry [2, 3]. While the concept of SOMA is simple – a capsule that contains a hidden needle, which would inject insulin once the device is in contact with the stomach wall, it has a well-thoughtout design. Let’s take a closer look at the challenging but successful journey of SOMA along the GI tract! After being swallowed, a SOMA would pass through the esophagus and enter the stomach. As the first step, the capsule would localize and self-orient its injection mechanism toward the stomach lining. This ingenious self-orientation system was inspired by the seemingly unrelated leopard tortoise (Stigmochelys paradalis). This tortoise species has a shifted center of mass and a steep-dome-shaped shell that allow it to always self-orient to a preferred upright position. Researchers applied computer models to optimize SOMA’s dome shape, and used a combination of lowdensity polycaprolactone and high-density stainless steel to lower its center of mass. Experiments showed that SOMA self-orientation only took one second. The second step is insulin injection. The needle inside the capsule has two components: a tip made of compressed insulin and a biodegradable shaft. Only the dissolvable insulin tip would pierce the stomach wall. To provide enough force for needle insertion into the stomach wall, the team further attached a compressed spring, which was initially fixed in sucrose and isomalt, to the needle. During actuation, water in the stomach would enter SOMA through its vents to dissolve the sugar barrier. This would release the spring and insulin would be injected into the stomach wall. The whole process required one minute and subsequent dissolution of the solid insulin drug lasted for about an hour under experimental conditions. After successful insulin delivery, the capsule would pass through the remainder of the GI tract and eventually be excreted in feces. “The design of SOMA sounds cool, but what’s the point of injecting insulin into the stomach wall instead of the abdomen? Needle injection is always painful!” You may have the same question in mind as you are reading through this

試想像如果你需要每週七天,每天四次在腹部進行注 射,你會感到害怕嗎?這正是第一型糖尿病患者所面對的困 境 [1]。由於身體無法產生足夠胰島素,這些患者需要通過 定期注射來降低血糖水平。 為了幫助第一型糖尿病患者,科學家和醫生幾十年來都 在尋找可靠的口服胰島素系統,可是極端 pH 值、蛋白酶以 及消化道的厚黏液層都為相關研究帶來巨大挑戰。 在 2019 年,麻省理工學院的研究人員發表了一項突 破性研究,他們設計了一種只有一顆藍莓大小,名為自我 定向毫米級投藥器(self-orienting millimeter-scale applicator,簡稱SOMA)的可服用裝置 [2, 3]。SOMA 麻雀雖小,但設計卻非常精巧 — 它是一顆包含隱藏針頭, 一與胃壁接觸就會注射胰島素的膠囊。讓我們仔細看看 SOMA 沿著消化道充滿挑戰但又成功的旅程吧! 患者吞服SOMA後,膠囊會沿食道進入胃部。 SOMA 第一步會自動將其注射裝置指向胃壁。這個巧妙 的自動導向系統靈感來自看似風馬牛不相及的豹紋陸龜 (Stigmochelys paradali),這種陸龜的低重心和陡峭的 圓拱形外殼使它始終能夠回到直立的狀態。研究人員以電 腦模型優化 SOMA的拱形,並用低密度聚己內酯和高密度 不銹鋼兩者的組合來降低重心。實驗結果顯示 SOMA 只需 一秒鐘就能自動導向。 Thinking Out of the Box Oral Insulin Pill article. Please rest assured that patients would not feel any pain as the stomach wall has no pain receptors. The effectiveness of stomach wall injection by SOMA was also proved to be comparable to conventional subcutaneous injection in pig studies. In fact, insulin is just one of the many drugs that could potentially be delivered by SOMA. To improve the applicability of SOMA, the team reported a new version of SOMA in 2021, the liquid-injecting SOMA (L-SOMA). It could deliver monoclonal antibodies in liquid form and at larger dosing volumes [4], implying that it could potentially target cancers and autoimmune diseases (e.g. rheumatoid arthritis) besides diabetes. The scope of applicable biomacromolecules further expanded to RNA in early 2022 [5, 6]. As single-stranded RNA is susceptible to degradation, researchers made use of protective polymeric nanoparticles to produce RNA-nanoparticle complexes. Results showed that SOMA was able to deliver these complexes into stomach cells at an amount comparable to that in COVID-19 vaccines. We are a step closer to oral mRNA vaccines now!

第二步是注射胰島素。膠囊內的注射針由兩個部分組 成:壓縮胰島素製成的針頭及可被生物降解的針桿,但只 有可溶解的針頭會刺入胃壁。為了提供足夠的力讓針頭刺 入胃壁,研究團隊將注射針和壓縮彈簧連接,彈簧起初被 蔗糖和異麥芽酮糖醇固定,在注射一刻胃部水份會通過 SOMA 的開口進入内部以溶解糖屏障,從而釋放彈簧將 胰島素注入胃壁,整個過程需時一分鐘,隨後固體胰島素 藥物在實驗條件下持續溶解大約一小時。成功輸送胰島素 後,膠囊會穿過餘下的消化道,最終隨糞便排出體外。 「SOMA 的設計聽起來很酷,但為甚麼要將胰島素注 射到胃壁而不是腹部呢?打針總是很痛的!」閱讀本文時, 您可能會想到同樣的問題。但請放心,由於胃壁沒有痛覺 感受器,患者並不會感到痛楚。在豬隻進行的研究也證明 SOMA 胃壁注射和傳統皮下注射成效相當。 事實上,胰島素也只是 SOMA 可運載的眾多藥物之 一。為了擴大SOMA 的應用範圍,研究團隊在 2021年 發表了新版本的SOMA — 液體注射SOMA(liquidinjecting SOMA,簡稱L-SOMA)。它能運送大劑量的 液態單克隆抗體 [4],意味著有望能針對除糖尿病外的疾 病,例如癌症和自體免疫疾病(類風濕關節炎等)。而在 2022 年初,RNA 成為了SOMA 能運送的生物巨分子之 一 [5, 6]。由於單鏈 RNA 容易被降解,研究人員利用以 聚合物製成的保護性奈米顆粒來造出 RNA-奈米顆粒複 合物。實驗結果表明 SOMA 能將與 2019 冠狀病毒病疫 苗相當劑量的複合物注入到胃細胞,意味著我們離口服 mRNA 疫苗又邁進一步了! References 參考資料: [1] American Diabetes Association. Insulin Routines. https:// insulin-other-injectables/insulin-routines. [2] Abramson A, Caffarel-Salvador E, Khang M, et al. An ingestible self-orienting system for oral delivery of macromolecules. Science. 2019;363(6427):611-615. doi:10.1126/science.aau2277 [3] Trafton A. New Pill can deliver insulin. MIT News. https:// [4] Abramson A, Frederiksen MR, Vegge A, et al. Oral delivery of systemic monoclonal antibodies, peptides and small molecules using gastric auto-injectors. Nature Biotechnology. 2021;40(1):103-109. doi:10.1038/s41587021-01024-0 [5] Abramson A, Kirtane AR, Shi Y, et al. Oral mRNA delivery using capsule-mediated gastrointestinal tissue injections. Matter. 2022;5(3):975-987. doi:10.1016/ j.matt.2021.12.022 [6] Trafton A. Making RNA vaccines easier to swallow. MIT News. 有何不可: 口服胰島素藥丸 7

Among the world’s ugliest animals, the blobfish will always be ranked near the top – one only needs to look at a single picture of them to understand. With their squashed flat bodies and bulging eyes, any measurement of beauty would put them into a disadvantaged position. Here are some facts about the blobfish, besides ugliness, that may surprise you. Blobfish and Where to Find Them Blobfish, fish in the family Psychrolutidae [1], lives at the bottom of the Atlantic, Pacific and Indian oceans [1-3]. They live at depths of approximately 600–1200 m under water, where the pressure is about 60–120 times that of atmospheric pressure [2, 4]. At this pressure, humans will surely be crushed to death, as our lungs will be unable to expand to breathe [2]. Little to no light reaches these depths; typically, beyond 200 meters, there is not enough light for photosynthesis to occur, and no light reaches beyond 1000 meters [5]. A research expedition at these depths would be too expensive, so very little is known about the blobfish and its habitat [3, 6]. About Mr. Blobby The current picture that we have of the blobfish (Psychrolutes microporos) is from a deep-sea trawl during a research expedition in 2003 [1]. The researchers affectionately named the fish Mr. Blobby [1], due to the (rather obvious) fact that it looks like, well, a blob. Despite Mr. Blobby’s fame (or infamy), we don’t even know whether Mr. Blobby is male or female, since no one is going to perform an autopsy on arguably the Internet’s most famous preserved fish specimen now [6]. Little is known about the blobfish’s biology. For example, how old can they get in general? Although another deep-sea fish, rougheye rockfish, which lives at depths of 150–450 m, can live for over 200 years! One thing we know, however, is that they are mostly a The World’s “Ugliest” Animals: The Blobfish Files 「醜陋」動物之最:水滴魚檔案 jelly-like mass with very little muscle. While most other fish have a swim bladder to maintain buoyancy, the blobfish doesn’t have one because gas-filled cavities would collapse under such an extreme pressure. The blobfish is instead a mass of mostly water and fat which offers a density slightly less than that of water, allowing it to float above the sea floor without much effort. The blobfish can be an ambush predators when it comes to hunting for snails, brittle stars, anemone and other bottom dwellers. As for reproduction, they lay eggs on rocks, thousands at a time, and expectant mothers would guard their nests together. Despite multiple campaigns striving to “Save the Blobfish”, the truth is that we don’t even have enough data to conclude whether it is an endangered species, and how bottom trawling and ocean acidification could affect the species [2, 7]. Whether Photo credit: Kerryn Parkinson, Australian Museum © NORFANZ Founding Parties By Sonia Choy 蔡蒨珩

9 there are millions or hundreds of blobfish in the world, nevertheless, one thing we must hold onto is to care for all animals, no matter their appearance. Just like humans, we can’t judge an animal by its cover, after all. The Psychology of Ugliness … and a Misunderstanding You might have seen videos of ugly animals around social media, but have you ever thought about why people even share them? At first thought, it seems like humans are programmed to appreciate beauty and therefore repel ugly things, but there seems to be a sort of “ugly-cute” that humans find endearing. These “ugly-cute” animals are usually characterized by big bulging eyes, large heads, and soft-looking bodies [8]. If these sound slightly familiar, it’s because things we consider cute and lovable, such as puppies and infants, also share the above characteristics. Ethologists suggested that humans are naturally built to take care of their offspring, so seeing these features causes a rush of emotion in us which manifests as cuteness [9]. So, it is no wonder that Mr. Blobby was voted the world’s ugliest animal by the Ugly Animals Preservation Society in 2013 – it is ugly, yes, but still endearing in a certain way. Yet, some might sill argue that Mr. Blobby is not ugly at all – in its usual habitat, it just looks like, well, a 水滴魚必定高踞世上最醜動物排行榜的頭幾位,任何 看過水滴魚照片的人都會清楚明白,牠們扁平的身軀和凸 出的眼睛,絕對不會符合任何學派對美學的描述。除了醜陋 的外貌外,以下是水滴魚令人驚嘆的二三事。 水滴魚與牠們的產地 水滴魚泛指隱棘杜父魚科(Psychrolutidae)的成員 [1],牠們住在大西洋、太平洋及印度洋的海底 [1-3],深度 約為 600–1200 米,那裡的水壓是大氣壓力的 60–120 倍 [2, 4],在這種壓力下人類肯定會被壓成一團而死,肺部 會因無法擴張而不能呼吸 [2]。光線亦很難到達這個深度: 基本上由 200 米起,熹微的光線已不足以支撐光合作用; 由1000米開始,海洋就只剩一片漆黑 [5]。由於在這種深 度進行考察的費用過於高昂,因此我們對水滴魚及其生境 的了解並不多 [3, 6]。 關於水滴先生 現時我們看見的水滴魚(Psychrolutes microporos) 照片來自2003年一次深海考察中的拖網打撈任務 [1]。當 時的研究員打趣地把這條魚取名為「水滴先生」(Mr. Blobby)[1],原因也不用多解釋,因為牠的 外型就像水滴一樣。 雖然水滴先生已經遐邇聞名(或是說因醜 陋的外表而聲名狼藉),但我們始終未能得知牠是 先生還是小姐,畢竟沒有人想解剖這個可能是在互聯 網上最有名的魚類標本 [6]。我們對這個物種的認識也不 深,譬如我們不知道水滴魚一般可以活多久,我們只知道另 一種住在水底150–450 米,叫阿留申平鮋的深海魚可擁 有長達 200 年的壽命!但有一件事我們是知道的,就是水 regular fish. The pressure of the deep sea helps hold the blobfish’s body together in a fish-like shape, but when it is dragged out of the water, the sudden drop of pressure causes its body to expand into a balloon, which looks very different from its usual appearance – just as humans would certainly look a bit squashed 1,200 m underwater. It is no surprise that even the photographer, Dr. Kerryn Parkinson, admitted that the famous picture of Mr. Blobby was no decent scientific image [6]. But seeing how loved Mr. Blobby is now across the world, it might not be a bad thing after all!

滴魚是擁有非常少肌肉的一團果凍狀物體。大部分魚類靠 魚鰾維持浮力,但水滴魚並沒有魚鰾,因為海底極端的水 壓會使任何空腔塌陷。反之,牠們身體幾乎就是由水分和 脂肪組成的混合物,因此牠們擁有一個稍稍低於海水的密 度,能不費吹灰之力就能浮在海床之上。另外,水滴魚是伏 撃型捕食者,會狩獵海螺、陽隧足(海蛇尾)、海葵,以及其 他居住在海床上的底棲生物。在繁殖方面,水滴魚會在岩 石上產卵,每次產上成千上萬顆,即將成為母親的水滴魚們 會成群保衛巢穴。 雖然人們舉辦了不同「救救水滴魚」行動,但其實我們 並沒有足夠資訊去判斷水滴魚是否瀕危物種,也不知道海 底拖網捕魚和海洋酸化將如何影響牠們 [2, 7]。然而,無論 地球上有數百萬條水滴魚也好,或只剩數百條也好,外表 漂亮或不討喜的動物都一樣值得人類保護;我們不能以貌 取人之餘,也不能「以貌取魚」。 醜陋心理學……一切只是一場誤會? 你可能已經在社交媒體看過一些載有醜陋動物的 片段,但你可曾想過我們為甚麼還會分享它們呢?乍想 之下,人類似乎與生俱來就會擁抱美麗的事物,而排斥 醜陋的;可是,醜陋之中又似乎有種惹人憐愛的「醜萌」 (ugly-cute)可以歸入可愛之列。這些「醜萌」的動物 通常擁有凸出的眼睛、巨大的頭顱和看似軟糯的身體 [8]。如果你覺得這些特徵似曾相識,可是因為我們覺得 可愛的東西,譬如嬰兒和小狗,都擁以上特質。動物行為 學家認為照顧後代是人類的天性,因此看到這些特徵會 觸發我們的情感,進而轉化為覺得對象「可愛」的觀感 [9]。由此觀之,水滴先生在 2013 年被醜陋動物保護協 會票選為「全球最醜的動物」也不是甚麼令人意外的事 情 — 沒錯,牠是醜陋,但某程度上亦是可愛。 然而還有人為水滴魚抱不平,說這完全只是一場誤 會,皆因水滴魚在自己的生境中根本一點也不醜:在深海 裡,牠的形狀就是正常的一條魚啊!深海的水壓把水滴魚 的身體壓成正常的「魚形」,但當被拉上水面時,周遭急 降的壓力卻使其身體像氣球般澎漲,漲得完全「不成魚 形」。如果我們反過來想想,人類在1200 米的深海裡想 必也「不似人形」吧。因此,水滴魚照片的拍攝者 Kerryn Parkinson 博士也承認那張爆紅的照片其實不是一張嚴 謹的科學照片 [6],但看見水滴先生如何受全世界網民的 愛戴,那張照片也許還不賴吧! 相片來源: Kerryn Parkinson, Australian Museum © NORFANZ Founding Parties

11 References 參考資料: [1] Australian Museum. (2022, April 28). Blobfish (aka Mr Blobby). fathead-psychrolutes-aka-mr-blobby/ [2] National Geographic. (n.d.). Blobfish. https://www. [3] Wood, C. (2021, December 8). What the Heck Is a Blobfish? Live Science. https://www.livescience. com/64817-blobfish.html [4] Schultz, C. (2013, September 13). In Defense of the Blobfish: Why the ‘World’s Ugliest Animal’ Isn’t as Ugly as You Think It Is. Smithsonian Magazine. https://www. [5] The National Oceanic and Atmospheric Administration. (2023, January 20). How far does light travel in the ocean? travel.html#:~:text=The%20aphotic%20zone%20exists%20 in,zone%20is%20bathed%20in%20darkness. [6] Dalton, A. (2022, February 28). “I try to find the beauty in everything”: Checking in on the fugly fish that broke the internet. Australian Geographic. https://www. i-try-to-find-the-beauty-in-everything-checking-in-onthe-fugly-fish-that-broke-the-internet/ [7] Taylor, I. (2022, February 10). The blobfish: A bloated guide to the world's ugliest animal (and what they really look like). BBC Science Focus. https://www.sciencefocus. com/nature/the-blobfish-a-bloated-guide-to-the-worldsugliest-animal/ [8] Langley, L. (2017, March 18). This Is Why We Find 'Ugly' Animals Cute. National Geographic. https://www. [9] Borgi, M., Cogliati-Dezza, I., Brelsford, V., Meints, K., & Cirulli, F. (2014). Baby schema in human and animal faces induces cuteness perception and gaze allocation in children. Frontiers in Psychology, 5, 411. https://doi. org/10.3389/fpsyg.2014.00411

You must have experienced the aftermath of a bowl of spicy ramen, a dollop of wasabi, a bite of chili pepper. Your tongue feels like it’s on fire; your eyes start watering, and you begin to sweat through your clothes. No other sensation would come close to the overwhelming sensory experience that comes with spiciness. Here is an interesting fact: Spiciness is not a taste, but rather a sensation of pain. Then, why does spiciness intrigue humans so much that we would prepare food “so tasty it hurts”? Chili peppers contain an alkaloid compound known as capsaicin, which can trigger the burning sensation of spiciness. As we chew, capsaicin molecules are released and spread across our tongue. However, they bypass the taste pores and bind to pain receptors instead [1]. Originally functioning as a detector to alert the brain of high temperatures (>43 °C [2]), these pain receptors, by the name of TRPV1, can also be activated by capsaicin. As a cation channel by nature, TRPV1 receptors will open when activated, so cations can diffuse into the nociceptive (pain-sensing) neurons [3]. The increase in electric potential, known as depolarization, will trigger the neuron to fire and send a signal to the brain. Our brain will then interpret the signal and think that our tongue is in contact with a burning hot substance, giving us the false impression that our mouth is on fire. If spiciness truly is a sensation of pain, why will we have the urge to go back for one last bite? Here’s where our body’s self-regulatory mechanism Understand Spiciness: A Pain but Not a Taste 辣……其實是一種痛? By Roshni Printer

13 comes into play. After perceiving that we are in pain, hormones like endorphins, which are known as the natural painkillers and the “feel-good” hormones of the body, are released [4]. These hormones also increase the level of a neurotransmitter, dopamine, making us feel even more pleasant and euphoric [4]. Therefore, the secret behind our addiction to spiciness is, in fact, the “feel-good” chemicals that give us a light-hearted rush. If your first instinct when your mouth is “on fire” is to grab a glass of water, think again! Capsaicin is a hydrophobic (“water-hating”, or “fat-loving”), non-polar molecule with a long hydrocarbon tail. Drinking water will only spread capsaicin all over the tongue, and heightens the burning sensation. You should instead consume dairy products because it contains casein, a non-polar protein which can bind to capsaicin. Similar to the cleaning action of detergents to remove grease, casein molecules will surround capsaicin molecules to form tiny droplets which can then be washed away easily [5]. Hence a cup of milk, or a cone of ice cream can likely “cool off” spicy food. Some foods may contain other compounds that can also activate TRPV1, and/or the “wasabi receptor” TRPA1, another pain receptor under the TRP family. Black peppers contain piperine [6], while mustard [7] and wasabi [8] contain compounds belonging to the class of isothiocyanates. Isothiocyanates are volatile small molecules that can be inhaled and stimulate the receptors in the nasal cavity, so mustard and wasabi can burn not only our mouth, but also our nose. Notably, this will eventually lead to the secretion of the “feel-good” chemicals as well. Alongside its ability to elicit a sensation of pain, surprisingly, capsaicin is also used in pharmaceuticals to provide relief to pain. It is commonly sold over the counter in the form of topical ointments and patches (the pain-relieving “hot” patches) [9]. In addition, capsaisin was approved in Europe to treat neuropathic pain [10], which is often described as shooting or burning pain, resulting from nerve injury [11]. Researchers have hypothesized how capsaicin works in relieving pain, with the desensitization of TRPV1 (i.e. decreased responsiveness after repeated exposure) being one of the possible mechanisms [9]. To conclude, the spicy capsaicin molecule can give us pleasure and pain at the same time. While scientists continue to unravel the working mechanisms of capsaicin and other pungent molecules in our body, we can, at least, take the lesson and keep a glass of milk handy next time when we feast on chili peppers! 如果你嚐過一碗地獄拉麵、一抹山葵或一口辣椒,當 時的辛酸你一定不會忘記:舌頭像被火燒一樣,淚水從眼 角滲出,汗水穿透衣服襲來;沒有一種官能刺激比辣更具 威脅性。告訴你一個有趣事實:與其說辣是一種味道,不 如說是一種痛。那到底是甚麼驅使人們烹調辛辣的食物, 自投痛楚的羅網呢? 辣椒含有一種叫辣椒素的生物鹼,它能觸發辣的灼熱 感。咀嚼會使辣椒素分子從食物中釋放,並擴散到舌頭的 每個角落。然而它們會繞過味覺感受器,並與痛覺感受器結 合 [1]。這些名為TRPV1的痛覺感受器原本的作用是在高 溫(>43°C [2])的情況下對腦部作出警告,但它們亦可以 被辣椒素觸發。作為正離子通道,TRPV1感受器被觸發時 會打開,令正離子得以擴散進入痛覺神經元 [3]。這個增加 電勢的過程叫去極化,會觸發神經元發出神經脈衝把信號 傳遞至腦部,腦部在詮釋信號後便誤以為我們的舌頭正與 灼熱的物件接觸,給予我們嘴巴被火燒的錯覺。 如果辣真的是一種痛,為甚麼我們會有多嚐一口的欲 望呢?那正是因為我們身體有一個自我調節系統:身體在 感到痛楚時會釋放安多酚等激素,安多酚既是天然止痛劑, 亦能帶來身心愉悅的感覺 [4]。同時,安多酚亦能提高多巴 胺這種神經遞質的水平,使我們更感愉快和興奮 [4]。因此, 令我們戀上吃辣的原因正是這些使我們自我感覺良好的化 學分子。 假如你在吃辣後的第一個反應是拿起一杯水來「救火」 的話,你可要再想想!辣椒素是帶有碳氫長鏈的疏水(亦即 親脂)非極性分子,喝水只會使辣椒素散落到舌頭的四周, 加劇灼熱感。你應該喝奶類製品,因為它們含有非極性的 酪蛋白,能與辣椒素結合。與清潔劑去除油脂的原理相近, 酪蛋白分子能包圍辣椒素形成微滴,然後能被輕易沖走

[5]。所以一杯奶,或一杯雪糕更能止辣。 也有一些食物含有其他能激發 TRPV1 的化合物,它 們有機會亦能觸發TRP家族中的另一種痛覺感受器 — 被稱為「山葵感受器」的TRPA1。黑椒含有胡椒鹼 [6], 芥末 [7]和山葵 [8]則含有屬於異硫氰酸鹽的化合物。 因為異硫氰酸鹽是細小的揮發性分子,能被吸進鼻腔並 刺激裡面的感受器,所以芥末和山葵不止能使口腔灼熱, 而且還會嗆鼻。值得留意的是這個過程最終也會令身體 釋放出使我們愉悅的化合物。 辣椒素既能觸發痛楚,亦意想不到地被用於製造鎮 痛藥物。這些產品多為非處方的外用軟膏及鎮痛貼(就 是常見的熱感鎮痛貼)[9]。此外辣椒素也在歐洲被批准 用於治療神經病變性疼痛 [10],一種源自神經損傷,經 常被形容為刺痛或帶灼熱感的疼痛 [11]。研究人員對辣 椒素的鎮痛原理提出了一些假設,當中 TRPV1 的去敏感 作用(即以重複刺激的方式去降低其反應)被認為是其 中一個可能的原理 [9]。 總括而言,辛辣的辣椒素分子既能給予我們愉悅的 感覺,亦能為我們帶來痛楚。在科學家繼續揭開辣椒素 和其他辛辣分子運作原理的同時,我們也許可以從中汲 取知識,最少懂得在下次麻辣大餐前準備好解辣用的 牛奶! References 參考資料: [1] Nobel Prize Outreach AB 2023. Press Release: The Nobel Prize in Physiology or Medicine 2021. The Nobel Prize. [2] Caterina MJ, Rosen TA, Tominaga M, Brake AJ, Julius D. A capsaicin-receptor homologue with a high threshold for noxious heat. Nature. 1999;398(6726):436-441. doi:10.1038/18906 [3] Caterina MJ, Schumacher MA, Tominaga M, Rosen TA, Levine JD, Julius D. The capsaicin receptor: a heatactivated ion channel in the pain pathway. Nature. 1997;389(6653):816-824. doi:10.1038/39807 [4] Choy M, El Fassi S, Treur J. An adaptive network model for pain and pleasure through spicy food and its desensitization. Cogn Syst Res. 2021;66:211-220. doi:10.1016/j.cogsys.2020.10.006 [5] Rohrig B. Hot Peppers: Muy Caliente. American Chemical Society. resources/highschool/chemmatters/past-issues/ archive-2013-2014/peppers.html [6] McNamara FN, Randall A, Gunthorpe MJ. Effects of piperine, the pungent component of black pepper, at the human vanilloid receptor (TRPV1). Br J Pharmacol. 2005;144(6):781-790. doi:10.1038/sj.bjp.0706040 [7] Eib S, Schneider DJ, Hensel O, Seuß-Baum I. Relationship between mustard pungency and allyl-isothiocyanate content: A comparison of sensory and chemical evaluations. J Food Sci. 2020;85(9):2728-2736. doi:10.1111/1750-3841.15383 [8] Uchida K, Miura Y, Nagai M, Tominaga M. Isothiocyanates from Wasabia japonica activate transient receptor potential ankyrin 1 channel. Chem Senses. 2012;37(9):809-818. doi:10.1093/chemse/bjs065 [9] O'Neill J, Brock C, Olesen AE, Andresen T, Nilsson M, Dickenson AH. Unravelling the mystery of capsaicin: a tool to understand and treat pain. Pharmacol Rev. 2012;64(4):939-971. doi:10.1124/pr.112.006163 [10] Chung MK, Campbell JN. Use of Capsaicin to Treat Pain: Mechanistic and Therapeutic Considerations. Pharmaceuticals (Basel). 2016;9(4):66. doi:10.3390/ ph9040066 [11] Jardín I, López JJ, Diez R, et al. TRPs in Pain Sensation. Front Physiol. 2017;8:392. doi:10.3389/fphys.2017.00392

By April Lam 林芷因 15 How Do Sticky Notes Work? 便利貼的原理是? Post-it notes are undoubtedly easy and convenient to use. Not only can they be placed anywhere without fasteners (i.e. tacks, paper clips, or staples), they do not easily fall off, nor leave any glue stains. Accepted as part of our many modern day conveniences, one rarely thinks about why this is possible in the first place. History of Sticky Notes Spencer Silver was a research chemist developing adhesives strong enough for aircraft construction [1]. In his attempts to invent such an adhesive, Silver instead discovered a weak adhesive that could be peeled on and off without losing its “stickiness [2].” While many may have thought this to be a useless invention, Silver’s colleague Art Fry gave him the idea of using the adhesive to create removable paper bookmarks for his choir hymn book. This moment in history led to the invention of Post-it notes. How to Describe the Strengths of Adhesives? Adhesives have two kinds of strengths that make up the adhesive bond: shear strength and peel strength. As illustrated in Figure 1, shear strength is measured by the forces pulling in a direction parallel to the two surfaces joined by the adhesive. Peel strength, on the other hand, is measured by the forces perpendicular to the two surfaces. For a Post-it note to be useful, it should have moderate shear strength to allow firm yet temporary attachment to a surface, while also having low peel strength to allow removal without tearing [3]. Why Are Polymer Adhesives Sticky? Before looking into the unique properties of sticky notes, let’s try to understand why they can stick to surfaces in the first place. Polymers are used as adhesives in the making of Post-it notes. These are large, long-chain molecules formed by repeating monomer units through a process called polymerization. When polymers come into contact with a surface, van der Waal’s forces will form between the polymers and the molecular surface of the object, causing them to stick together. Almost all polymer adhesives work using these interactions [4]. When producing polymer adhesives for a specific purpose, scientists typically mix different ratios of monomers to modify the properties of the resulting polymer. This process results in a copolymer, defined as polymers formed from more than one type of monomer. To produce the adhesive mixture to be sprayed on sticky notes, Silver found the ideal ratio to be 95 to 99 percent of acrylate monomer, and 1 to 5 percent of mixtures containing ionic monomers and maleic anhydride [5]. In other words, small amounts of acrylate monomers are substituted with ionic monomers and maleic anhydride to form long, crosslinked chains. Such modifications can improve the elastic properties of the copolymer, and allow the adhesive to be produced as an aerosol spray [5]. How Do Sticky Notes Work? But why can you stick and unstick a Post-it effortlessly? The copolymer is actually produced in the form of microspheres with diameters as small as 50 to 75 µm [6]. A single layer of sparsely spaced microspheres are sprayed on the paper of the Postit note, which looks like the bumpy surface of a basketball under a microscope, with little glue bubbles Figure 1 Shear Strength and Peel strength. Shear Strength Peel Strength