科学家正在比以往任何时候更为接近制造出首件隐身衣的目标。《自然》杂志现在披露，两个不同的小组(一个在新加歧，另一个在伯明翰大学和伦敦帝国学院)都已使直径数厘米的物体隐形。“毛毯斗篷”(科学家们倾向这种称呼)通过弯曲进入和离开斗篷光线的方式来使物体隐形。


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科学家即将制造出首件隐身衣

　　科学家正在比以往任何时候更为接近制造出首件隐身衣的目标。科学家在过去用可引导和控制光谱特定部分传播和传输的不同材料进行了实验，它们可以用来使一个物体看起来隐形。报道称，苏格兰圣安德鲁斯大学的科学家在安德烈-迪-法尔科的领导下研制出一种他们称之为“超弯曲材料(Metaflex)”的弹性隐形衣材料，这可能使其商业和工业应用的前景大幅提前。
　　《自然》杂志现在披露，两个不同的小组(一个在新加歧，另一个在伯明翰大学和伦敦帝国学院)都已使直径数厘米的物体隐形。他们称他们作到这一点是因为方解石晶体的特性。方解石是一种用于制造碳酸钙的廉价和常见的材料。
　　“毛毯斗篷”(科学家们倾向这种称呼)通过弯曲进入和离开斗篷光线的方式来使物体隐形。方解石有一种特别的光学特性，光线在这种情况下被如此地弯曲，以致于光线看上去是从物体之下的地面直接反射回来一样，换句话说，物体好像不存在。
　　新麻联盟科研中心的小组已用方解石材料制造出一种毛毯斗篷，它可以在红色、绿色、蓝色的可见光下隐藏一个38毫米长、2毫米高的小钢楔。它的设计用途是在水下工作。帮助研发这一灵巧斗篷的机械工程师乔治-巴巴斯塔蒂斯称：“我认为**可以对能在海底下掩盖物体的斗篷进行多项应用，不过，我不想具体猜测他们想掩盖什么东西。”
　　Invisibility cloaks Now you see me, but for how much longer
　　Scientists are racing to perfect practical cloaking devices that can hide objects from sight by bending rays of light
　　They won't help you sneak around Hogwarts unobserved. Nor will they help a Klingon spaceship attack the USS Enterprise without being detected. Nonetheless, scientists are getting ever closer to fabricating the first practical invisibility cloaks。
　　In the past, scientists have experimented with different metamaterials that can direct and control the propagation and transmission of specified parts of the light spectrum – and could be used to render an object seemingly invisible. Last month, scientists at the University of St Andrews in Scotland led by Dr Andrea Di Falco reported the creation of a flexible cloaking material they call "Metaflex", which may bring commercial and industrial applications significantly closer。
　　Now the journal Nature has revealed that two separate groups – one based in Singapore and the other at the University of Birmingham and Imperial College London – have made objects each a few centimetres in diameter invisible. They credit the special properties of calcite crystals – and calcite is a cheap and common mineral made of calcium carbonate。
　　"Carpet cloaks" – scientists' preferred term – render covered objects invisible by bending light rays as they enter the cloak and then when they exit it. Calcite has special optical properties and in this instance light is bent in such a way that the rays seem to have been reflected directly from the ground below the object – as though it was not there, in other words。
　　The team at the Singapore-MIT Alliance for Research and Technology (Smart) has built a calcite carpet cloak that can shield a small steel wedge measuring 38mm by 2mm from red, green and blue visible light. It is designed to work under water。
　　"I think governments could make a lot of use out of a cloak that can hide objects on the seabed, although I won't speculate on exactly what they may want to hide," George Barbastathis, a mechanical engineer who helped develop the Smart cloak, told Nature。
　　Cloaking devices are keenly awaited and coveted by the military. Defence chiefs believe such devices will usher in a new age of stealth technology and allow them to hide planes, ships, spacecraft, tanks and other vehicles from radar. More advanced versions could ultimately be good enough to make objects or troops invisible to observers, it is believed。
　　The Birmingham and Imperial team, led by theoretical physicist Sir John Pendry, a pioneer in this field, has constructed a calcite cloak that manages to hide objects that are several centimetres in height. Their cloak only works in the air。
　　Hopes of developing fully functional invisibility cloaks in the near future have been further boosted by the fact that both the Singapore and London devices turned out to be much cheaper to make than earlier attempts. Those first versions were built using intricately fabricated and highly expensive silicon microstructures。
　　By contrast, the materials needed to make the Smart team's cloak cost less than ￡1,000, according to Baile Zhang, another member of the team, because calcite is inexpensive。
　　"It's not quite easy enough to make at home, but it's not too far off," Zhang said。
　　One of the concerns about cloaking used to be that people would only be able to cloak microsize objects. But according to physicist Michal Lipson of Cornell University, New York, these new breakthroughs point to an exciting future. "We are close to cloaking objects that we are familiar with in everyday life," Lipson said。
　　(卫报)