美研制出像皮膚一樣可自愈的新塑料

美研制出像皮膚一樣可自愈的新塑料

據美國物理學家組織網近日報道，“一種新型塑料可模仿人體皮膚，當被劃傷或割傷時會‘出血’變紅以警示受傷，而創面觸光后又可自愈合，這為飛機、汽車、手機、筆記本電腦和其他產品提供了理想的自修復表面。”這是美國南密西西比大學一個研究小組的科研人員在第243屆美國化學協會全國會議及博覽會上的描述。

塑料的應用已非常普遍，由于其結合了強度大、重量輕、耐腐蝕等多種優良特性于一身，可替代鋼、鋁、玻璃、紙等傳統材料。然而，科學家也一直在努力修正這些隨處可見的材料的一大缺點：許多塑料一旦被刮傷或破裂，修復會很困難或根本不可能。

自愈塑料已成為材料科學的圣杯。實現這一目標的方法之一是在裂痕或劃傷處破開引晶塑料膠囊，其可釋放出使傷痕愈合的化合物。另一種方法是使塑料經光、熱或化學制劑等外部刺激而進行自修復。

這項研究的首席研究員馬雷克教授說：“大自然賦予各種生物系統自我修復的能力，例如皮膚受傷后自愈和樹干被切割后長出新樹皮，還有一些雖看不到，但卻在幫助我們維護生命和健康，像DNA（脫氧核糖核酸）用以修復基因遺傳損傷的自愈系統。這種新型塑料可以模仿大自然中的這種能力，當受損時會顯示紅色警示信號，然后將其暴露于可見光或變化溫度和pH值，可促其自我修復。”

該研究小組開發的塑料是用很小的分子鏈接或架“橋”于塑料化學物質上組成長鏈，當塑料被劃傷或破裂，這些環節會被打破而改變形狀，進而產生可見的顏色變化，裂口周圍會出現紅色斑點。而暴露在普通日光或燈光下或者pH值、溫度發生變化時，其內“橋梁”會重建，損傷得以愈合，紅色標記自行消除。

這種可顯示受傷警告并具備自我修復能力的塑料可廣泛應用于很多領域，例如汽車擋泥板上的劃痕，可能只需將其暴露在強光下即可自行修復；飛機關鍵部件受損后裂縫邊緣會顯示出紅色警示標記，便于工程師決定是用照燈的方式“治愈”損傷，還是進行完整的組件更換；此外還可能大量應用于戰場上的武器系統。

新型塑料不像依靠嵌入式愈合化合物只能自修復一次，而是可以反復進行修復；同時相比許多其他塑料更為環保，因為其生產過程基于水性塑料，而不是依賴于潛在的有毒成分。該研究團隊現正在引進其他技術來生產可以承受高溫的塑料。

New plastics 'bleed' when cut or scratched — and then heal like human skin

new genre of plastics that mimic the human skin's ability to heal scratches and cuts offers the promise of endowing cell phones,laptops, cars and other products with self-repairing surfaces,scientists reported today. The team's lead researcher described the plastics, which change color to warn of wounds and heal themselves when exposed to light,here today at the 243rd National Meeting & Exposition of the American Chemical Society (ACS),the world's largest scientifi c society.

"Mother Nature has endowed all kinds of biological systems with the ability to repair themselves," explained Professor Marek W. Urban, Ph.D., who reported on the research. "Some we can see, like the skin healing and new bark forming in cuts on a tree trunk. Some are invisible,but help keep us alive and healthy,like the self-repair system that DNA uses to fix genetic damage to genes. Our new plastic tries to mimic nature, issuing a red signal when damaged and then renewing itself when exposed to visible light,temperature or pH changes."

Urban, who is with the University of Southern Mississippi in Hattiesburg foresees a wide range of potential applications for plastic with warn-and-selfrepair capabilities. Scratches in automobile fenders, for instance,might be repaired by simply exposing the fender to intense light.Critical structural parts in aircraft might warn of damage by turning red along cracks so that engineers could decide whether to shine the light and heal the damage or undertake a complete replacement of the component. And there could be a range of applications in batile fi eld weapons systems.

Plastics have become so common, replacing steel,aluminum, glass, paper and other traditional materials because they combine desirable properties such as strength, light weight and corrosion resistance. Hundreds of scientists around the world have been working, however, to remedy one of the downsides of these ubiquitous materials: Once many plastics get scratched or cracked, repairs can be diffi cult or impossible.

Self-healing plastics have become a Holy Grail of materials science. One approach to that goal involves seeding plastics with capsules that break open when cracked or scratched and release repairing compounds that heal scratches or cuts. Another is to make plastics that respond to an outside stimulus — like light, heat or a chemical agent — by repairing themselves.

Urban's group developed plastics with small molecular links or "bridges" that span the long chains of chemicals that compose plastic. When plastic is scratched or cracked, these links break and change shape. Urban tweaked them so that changes in shape produce a visible color change — a red splotch that forms around the defect. In the presence of ordinary sunlight or visible light from a light bulb, pH changes or temperature,the bridges reform, healing the damage and erasing the red mark.

Urban cited other advantages of the new plastic. Unlike selfhealing plastics that rely on embedded healing compounds that can self-repair only once, this plastic can heal itself over and over again. The material also is more environmentally friendly than many other plastics, with the process for producing the plastic water-based,rather than relying on potentially toxic ingredients. And his team now is working on incorporating the technology into plastics that can withstand high temperatures.