딱정벌레(Cyphochilus) 등껍질의 비밀 "투명 망토도 만든다"…

2009년 6월 19일 오후 1:29공개조회수 5 0

"투명 망토도 만든다"… 딱정벌레(Cyphochilus) 등껍질의 비밀 표면 비늘구조 모방해 흰 종이 코팅재 만드는 등 신기술 응용 재료로 각광 동남아시아에는 온몸이 하얀 딱정벌레(Cyphochilus)가 있다. 서식지의 흰색 곰팡이 무리에 몸을 숨기기 위한 일종의 보호색이다. 과학자들은 등껍질의 독특한 표면 구조가 흰색의 비결임을 밝혀냈다. 한 기업이 이 딱정벌레를 모방해 흰 종이를 만드는 새로운 코팅 물질을 개발했다. 미국에선 사막에 사는 딱정벌레의 등에 나 있는 돌기 구조를 모방해 방수(防水)·항균(抗菌) 코팅재를 만들고 있다. 딱정벌레가 신기술의 보고(寶庫) 역할을 하는 셈이다. ◆흰색 등껍질 모방한 흰 종이 코팅재 프랑스 이머리 미네랄(Imery Minerals)사와 영국 엑서터대 공동 연구진은 광학분야 국제학술지인 '어플라이드 옵틱스(Applied Optics)' 최신호에 발표한 논문에서 "흰색 딱정벌레의 표면 구조를 모방해 흰 종이를 만드는 코팅 기술을 개발했다"고 밝혔다. 자연이든 인공이든 색은 색소(色素)나 규칙적인 구조를 가진 광결정(光結晶)에서 비롯된다. 예를 들어 색소나 광결정이 붉은색 파장의 빛만 반사하면 우리 눈에 붉은색으로 보인다. 하지만 흰색은 모든 파장의 빛이 다 반사될 때 나타난다. 엑서터대의 피트 부쿠직(Vukusic) 교수는 2007년 딱정벌레의 표면에 있는 불규칙적인 비늘들이 모든 빛을 반사해 딱정벌레가 흰색이 된다는 사실을 밝혀냈다. 연구진은 이번엔 광물질로 비늘 구조를 모방해 종이에 코팅했다. 그러자 우유보다 더 하얀색이 나타났다. 광물질은 딱정벌레의 비늘처럼 불규칙한 구조를 가지면서도 적당한 간격으로 떨어져 있다. 이렇게 하면 모든 파장의 빛을 반사한다. ▲ 딱정벌레가 신기술의 보고로 떠오르고 있다. 온몸이 하얀 딱정벌레의 표면구조를 모방해 종이를 하얗게 만드는 코팅재가 개발됐다. 또 비단벌 레에서처럼 화려한 색깔을 만드는 광결정 구조를 모방해 광통신 소자와 투명망토 물질이 개발되고 있다./영 엑서터대 제공 딱정벌레를 모방한 코팅물질은 종이 무게를 줄이는 효과도 있다. 딱정벌레 비늘의 두께는 머리카락 굵기의 10분의 1에 불과하다. 현재는 흰색을 내기 위해 탄산칼슘 같은 광물질을 종이에 코팅하는데, 두께가 비늘의 두 배나 된다. 딱정벌레 모방 물질을 쓴 흰 종이는 코팅이 훨씬 얇으니 그만큼 무게가 덜 나간다. 덕분에 종이 운송비용도 줄어든다. 부쿠직 교수는 "자연은 영감을 줄 디자인들로 가득 차 있다"며 "흰색 딱정벌레는 대학의 기초연구와 산업적 응용 사이의 거리를 이어준 것"이라고 밝혔다. ◆사막 딱정벌레는 항균 필름으로 발전 딱정벌레를 모방한 항균 코팅재도 개발 중이다. 미국 매사추세츠공대(MIT) 마이클 루브너(Rubner) 교수 연구진은 사막에 사는 딱정벌레의 등 구조를 모방해 안개에서 물을 만드는 필름을 만든 데 이어, 최근에는 같은 방법으로 세균이 달라붙지 못하게 하는 코팅제도 개발 중이다. ▲ 남아프리카 사막에 사는 스테노카라 딱정벌레. 등껍질의 돌기 덕분에 안개에서 물을 뽑아낼 수 있다. 이를 모방한 방수·항균 코팅재가 개발 중이다./영 옥스퍼드대 제공 남아프리카 나미비아 사막에 사는 딱정벌레는 등에 나 있는 돌기를 이용해 물을 만든다. 돌기 끝은 물과 잘 달라붙지만 돌기 아래 홈은 물을 밀어낸다. 딱정벌레가 안개 낀 날 바람 부는 쪽으로 등을 세우면 돌기에 물방울이 맺힌다. 점점 더 커진 물방울은 아래쪽으로 굴러 떨어져 딱정벌레 입으로 간다. 루브너 교수팀은 2006년 고분자물질로 딱정벌레 등처럼 미세한 돌기가 나 있는 필름을 만들었다. 돌기에는 작은 구멍을 뚫어 맺힌 물방울이 빠지게 했다. 연구진은 이후 돌기에 항균물질을 입히는 연구를 하고 있다. 돌기 아래 홈에는 물이 들어가지 못한다. 때문에 물방울은 돌기에 위태롭게 붙어 있다가 무거워지면 바로 굴러 떨어진다. 연잎도 같은 구조다. 물방울이 굴러 떨어지면 잎 표면에 맺힌 오물이나 세균들도 함께 쓸려 간다. 여기에 항균물질이 첨가되면 세균이 얼씬도 못하게 할 수 있다. 병원이나 주방, 부엌 표면을 이런 고분자 필름으로 코팅하면 방수와 항균 두 마리 토끼를 잡을 수 있다. ◆투명망토 만드는 자연의 광결정 원래 딱정벌레는 등껍질의 광결정 덕분에 과학자들의 주목을 받았다. 껍질에 있는 광결정이 특정 파장의 빛만 반사해 보석처럼 화려한 색을 띠게 한다. 보석 오팔이나 물포나비 날개도 같은 구조다. 이를 모방해 빛을 이용한 광통신 회로나 발광다이오드(LED)의 효율을 높이려는 연구가 진행 중이다. 국내에선 이화여대 우정원 교수가 딱정벌레 광결정에서 아이디어를 얻어 전자 대신 빛을 이용하는 반도체 다이오드를 개발했다. 우 교수는 "요즘 광결정 연구는 투명망토 연구에 집중되고 있다"고 말했다. 광결정으로 빛이 물체에 부딪히지 않고 휘어 돌아가게 하면 우리 눈엔 물체가 없는 것으로 보인다. 우 교수는 "딱정벌레가 투명망토로 이어진 셈"이라고 말했다. 조선일보 Nature's Whitest White Found in Ghostly Beetle By Charles Q. Choi, Special to LiveScience The bright whiteness of the Cyphochilus beetle is unusual in nature. Credit: P. Vukusic-University of Exeter Full Size 1 of 2 The bright whiteness of the Cyphochilus beetle is unusual in nature. Credit: P. Vukusic-University of Exeter The whiteness comes from the scales that cover the beetlea€™s body, head and legs. Credit: P. Vukusic-University of Exeter A beetle with scales as pale as a ghost could help engineers come up with super-thin, paper-white paints, new research shows. The long, flat overlapping scales that cover the head, body and legs of the white Cyphochilus beetle, a common sugarcane pest in Southeast Asia, are brighter than milk, pearly teeth or most other white substances found in nature, says Pete Vukusic, an optical physicist at Exeter University in England. These scales are extraordinarily thin, roughly half the width of a red blood cell. This makes them at least 100 times thinner than any whitening and brightening agents invented as yet. And they could inspire advances that improve the paper we write on, the color of our teeth and possibly the brightness of lights and displays in the future, Vukusic said. Mimicking nature In recent years, many scientists have looked to nature for new engineering designs, developing such materials as adhesives based on geckos foot pads and easy-clean fibers inspired by tiny bumps on lotus leaves. Vukusic decided to focus on color-manipulation and color-flow structures that nature developed, "since it surely must have come up with some really good ideas. We know structural color in butterflies dates back at least 50 million years," he told LiveScience. Most color in animals often comes from pigments, which absorb specific wavelengths of light and reflect others. Other colors in animals come from minute structures they possess that make incoming wavelengths of light interact with each other, causing some to emerge weakened and others strengthened. Familiar examples of structural color are seen with soap bubbles and peacock feathers. Vukusic explored nature for a structure that generated the color white since it is relatively uncommon in animals. The colors that creatures adopt often help protect them by serving as camouflage. "White backgrounds are not generally found in, say, savannahs," Vukusic said. A simple Internet search helped Vukusic arrive at the Cyphochilus beetle. "The brilliant white of the beetle was just striking to me," he recalled. "I know images can be doctored, but it seemed as if this could be very special. So I just ordered a few for $1.50 each." He noted that the beetle's whiteness might have evolved to help it blend in with local white fungi. Beetle-scale balance In order to appear white, a substance has to scatter all colors of light randomly at the same time. Using electron microscopes, Vukusic and his colleagues found that the scales of the Cyphochilus beetle possess structures made of randomly oriented filaments. The beetle's scales carefully balance the size of the filaments and spaces between them. This means these structures scatter light far more efficiently than, say, a milk tooth from collaborator Benny Hallam's son, enabling the scales to generate a brilliant white even when very thin--in this case, five millionths of a meter. Future research could help devise extraordinarily bright white synthetic materials. These could, for instance, help reflect light, replacing the bulky glass mirrors at times found in flat-panel displays, Vukusic said. Vukusic, Hallam and their colleague Joe Noyes reported their findings in the latest issue of the journal Science. Beetle shell inspires brilliant white paper June 10th, 2009 Enlarge These are cyphochilus beetles. Credit: Professor Pete Vukusic, University of Exeter An obscure species of beetle has shown how brilliant white paper could be produced in a completely new way. A team from Imerys Minerals Ltd. and the University of Exeter has taken inspiration from the shell of the Cyphochilus beetle to understand how to produce a new kind of white coating for paper. Ads by Google Decision Support by FICO™ - Why your Business needs Business Rules. Free White Paper by FICO™. - www.FICO.com SAP White Papers - Download the latest white papers for SAP professionals worldwide - whitepapers.sapinsideronline.com The Cyphochilus beetle has a highly unusual brilliant white shell. In 2007, research by the University of Exeter and Imerys Minerals Ltd., published in leading journal Science, revealed how the beetle produced its brilliant whiteness using a unique surface structure. Native to south-east Asia, it is believed that the beetle's whiteness evolved to mimic local white fungi as a form of camouflage. New research, now published in the journal Applied Optics, shows how some of the beetle's shell structure can be mimicked to produce coatings for white paper. At one　　　 200th of a millimetre thick, the beetle's scales are ten times thinner than a human hair. Good quality white paper is coated with a mixture of white mineral particles such as calcium carbonate and kaolin. Using conventional production methods, industrial mineral coatings for high quality paper would need to be twice as thick as the beetle shell to be as white. The team has now shown that through careful mineral selection and processing, it is possible to mimic some of the structure of the white beetle's shell to produce an enhanced bright white coating for paper. This higher performance could result in lighter weight paper with a very high degree of whiteness. Lighter paper would also reduce transportation costs, simultaneously reducing the economic and environmental cost of manufacture. Colour in both nature and technology can be produced by pigmentation or by very regularly arranged layers or structures. Whiteness, however, is created through a random structure, which produces 'scattering' of all colours simultaneously. Studies of the beetle's body, head and legs showed them to be covered in long flat scales, which have highly random internal 3D structures. These irregular internal forms are the key to its uniquely effective light scattering. By balancing the size of the structures with the spacing between them, they scatter white light extremely efficiently. The key to producing the optimal white coating for paper is in the design of the constituent mineral particles. "White paper coatings must provide the right balance between the size, number density and separation of the scattering units in the coating - as found in the beetle's scales", said Dr Benny Hallam, Application Support Manager of Imerys Pigments for Paper Europe Technology Group. Some of the beetle's design protocols could be utilised already with tailor-made mineral designs such as Imerys' CarboFlexTM range. The company is now planning to assess the feasibility of taking these design protocols to the next level in order to produce beetle-inspired ultra-white coatings on a large scale. Biomimicry of white beetle could produce whiter teethRhett A. Butler, mongabay.com January 18, 2007 A pure white beetle found in the forests of southeast Asia could eventually lead to "brilliant white ultra-thin materials" including whiter teeth and finer paper, according to research led by scientists at the University of Exeter. Writing in the January 19 issue of the journal Science, researchers describe the ultra-thin surface structure of the brilliant white shell of the Cyphochilus beetle and note that mimicry of its scales could produce thinner, whiter coatings. A news release from the University of Exeter elaborates: At one　　 200th of a millimetre thick, the beetle's scales are ten times thinner than a human hair. Industrial mineral coatings, such as those used on high quality paper, plastics and in some paints, would need to be twice as thick to be as white. Close up of the Cyphochilus beetle. Whiteness is relatively rare in animals but researchers say the Cyphochilus has developed scales that effectively scatter all visible wavelengths of light in order to appear white. Its white color helps the insect better camouflage among white fungi found in its native habitat. Image copyright Pete Vukusic of the University of Exeter.

"This kind of brilliant whiteness from such a thin sample is rare in nature. As soon as I saw it, every instinct told me that the beetle was something very special," said Dr Pete Vukusic of the University of Exeter's School of Physics and lead author of the paper. "In future, the paper we write on, the colour of our teeth and even the efficiency of the rapidly emerging new generation of white light sources will be significantly improved if technology can take and apply the design ideas we learn from this beetle."

Vukusic says that the flat, overlapping scales that cover the beetle's body, head and legs are structured to scatter all visible wavelengths of light in order to appear white. The scattering by the scales is far more efficient than the fibers in white paper or the enamel on teeth, according to Vukusic.

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