就像任何设计电脑筹码的人为生，詹姆斯迈尔斯就是他的核心，是一个硅片。 “硅是辉煌的，”他说。辉煌是因为它是一种自然的半导体，可以通过沟通电力并充当绝缘体，这取决于条件 - 并且因为它可以以小规模设计。辉煌，因为它是地球上的第二个常见的元素，可能现在紧紧抓住脚底，并通过加热沙子轻松生产。这些属性已经使我们今天几乎所有技术的基岩都造成了。像英国半导体公司的工程师这样的人，大多花时间考虑如何将更多的硅包装成更少的空间 - 在20世纪70年代到今天的数十亿到数十亿到数十亿的倒数3月份。随着摩尔的法律，我们是，因为迈尔斯，“在硅中游泳。”
为什么转回技术时钟？因为现代硅芯片是脆性的，所以晶片不灵活的电子产品。在压力下，他们紧缩。虽然硅是便宜的，但越来越便宜，有一些用例可能永远不够便宜。考虑一个电脑芯片放置在牛奶纸盒内，用传感器替换印刷的有效期，检测腐败的化学迹象。有用？ sorta！但如果成本最小，这只值得增加数十亿块牛奶。一个应用臂正在测试是一种胸部安装的芯片，其针对心律失常监测患者 - 一种不一致的，宜光的心脏跳动 - 并且在几个小时后被丢弃。为此，你想要一台便宜但更重要的是一个弯曲的电脑。 “它需要和你一起移动而不会弹出，”Myers说。
理论上，许多材料可以满足这些需求。研究人员已经从有机材料和设计的基板中建造了晶体管 - 这是晶体管换出金属箔甚至纸张的晶片。周三描述的芯片迈尔斯的团队由金属氧化物制成的“薄膜晶体管” - 一种铟，镓和锌的混合物 - 这可以比其硅对应物更薄。基材是聚酰亚胺，一种塑料，而不是硅晶片。它便宜，薄，灵活 - 以及工程师的一点痛苦。塑料在较低的温度下熔化比硅，这意味着一些涉及热量的生产技术不再可用。薄晶体管可能包含缺陷，意味着能量不能通过芯片制造商期望的方式移动。与现代芯片相比，设计也使用了更多的功率。这些是20世纪70年代和80年代的芯片制造商在20世纪70年代和80年代的同样的问题。他现在可以同情他的老同事。
与硅设备的一致性是关键，解释了Cherine Ramsdale，该研究和务实的技术高级副总裁们，设计和生产了柔性芯片。虽然这些材料是新的，但这些想法是尽可能地借用硅芯片的生产过程。这样，更容易生产芯片en masse并按住成本。 Ramsdale表示，由于便宜的塑料和设备需求，所以这些筹码可能会花费大约十分之一。她说，是，是的，“务实”的事情。
斯坦福大学的材料科学家埃里克流行音乐并没有参与研究，他对芯片的复杂性和它包含的晶体管的复杂性印象深刻。 “这推动了技术前进，”他说。但实用主义有限。最清晰的是设备使用的能量。该芯片消耗了21毫瓦的功率，但只有1％的时间达到了执行计算;随着芯片闲置，其余的浪费了。这可以由太阳能电池生产的邮票小于户外邮票，他换句话说，这并不多 - 但它不是效率的巨大起点，因为灵活的筹码变得更加复杂。 “你打算做什么，把自己挂着到一个巨大的电池？” POP问。
Myers表示，这些小型芯片的计划是使用类似于使用智能手机支付的技术的技术使用无线充电。但他承认芯片需要更节能 - 他认为可以是一点。他说，目前的设计可以使电流设计更小，更高效，也许足以扩展到100,000个门。但这可能是极限。原因是它相当简单的设计。晶体管有两个味道，称为“n”和“p”。他们互相补充。当没有电压而关闭时，有机打开;其他类型对面。 “你真的想拥有它们，”Pop说。手臂芯片泄漏的一个原因是它的能量是它只有n型。使用材料臂和务实的P型晶体管更难以工程师。
Subashish Mitra是2013年斯坦福的计算机科学家，2013年领导了碳纳米管电脑的第一次演示，而ARM的设计似乎没有展示任何理论突破，研究人员似乎生产了一种相对容易制造和可用的设备对于实际应用。 “时间将告诉应用程序开发人员如何利用这一点，”Mitra说。 “我认为这就是令人兴奋的一部分。”
POP解释，哪种柔性材料最终是依赖于如何使用芯片的使用方式。例如，硅并不总是注定在我们的设备的核心。一时，科学家认为这将是锗 - 一个元素，是硅的上半导体。但它不称为“锗谷”。硅原始更容易获得，并且在某些方面，更容易工程师。便宜，灵活的芯片在他们自己的早期阶段。我们希望纸质电子产品的可回收性吗？碳纳米管的潜在功率和规模？或者我们只需要塑料的实用性。
Like anyone who designs computer chips for a living, James Myers is, at his core, a silicon guy. “Silicon is brilliant,” he says. Brilliant because it’s a natural semiconductor—able to both conduct electricity and act as an insulator, depending on the conditions—and because it can be engineered at small scale. Brilliant because it is the second-most-common element on Earth, probably clinging to the soles of your feet right now, and easily produced by heating sand. Those attributes have made it the bedrock of virtually every technology we use today. People like Myers, an engineer at the British semiconductor firm Arm, mostly spend their time thinking about how to pack more silicon into less space—an exponential march from thousands of transistors per chip in the 1970s to billions today. With Moore’s law, we are, as Myers puts it, “swimming in silicon.”
For the past few years, however, Myers has been looking beyond silicon to other materials, like plastic. That means starting again from the beginning. A few years ago, his team began designing plastic chips that contained dozens of transistors, then hundreds, and now, as reported in Nature on Wednesday, tens of thousands. The 32-bit microprocessor contains 18,000 logic gates—the electrical switches you get from combining transistors—and the basic lobes of a computer brain: processor, memory, controller, inputs and outputs, etc. As for what it can do? Think desktop from the early 1980s.
Why turn back the technological clock? Because modern silicon chips are brittle, inflexible wafers of electronics. Under stress, they crunch. And while silicon is cheap, and getting cheaper, there are some use cases where it may never be cheap enough. Consider a computer chip placed inside a milk carton, replacing a printed expiration date with a sensor that detects chemical signs of spoilage. Useful? Sorta! But it’s only worth adding to billions of cartons of milk if the cost is minimal. One application Arm is testing is a chest-mounted chip that monitors a patient for arrhythmia—an inconsistent, lilting heart beat—and is meant to be discarded after a few hours. For that, you want a computer that’s cheap but, even more importantly, one that bends. “It needs to move with you and not pop off,” Myers says.
A number of materials could theoretically meet those needs. Researchers have built transistors from organic materials and designed substrates—that’s the wafer the transistors go into—out of metal foils and even paper. The chip Myers’ team described Wednesday is composed of “thin-film transistors” made from metal oxides—a mix of indium, gallium, and zinc—that can be made thinner than their silicon counterparts. The substrate is polyimide, a kind of plastic, rather than a silicon wafer. It’s cheap, thin, and flexible—and also a bit of a pain to engineer. Plastic melts at a lower temperature than silicon, meaning some production techniques involving heat are no longer usable. And the thin transistors may contain imperfections, meaning energy doesn't move around the circuitry in ways that chipmakers expect. Compared with modern chips, the design also uses a lot more power. These are the same issues that bedeviled chipmakers in the 1970s and ’80s, Myers points out. He can now sympathize with his older colleagues.
Compared with the billions found in modern 64-bit silicon processors, 18,000 gates doesn’t sound like much, but Myers speaks of them with pride. Sure, the microprocessor doesn’t do much; it just runs some test code he wrote five years ago that makes sure all the components are working. The chip can run the same sort of code as one of Arm’s common, silicon-based processors.
That consistency with silicon devices is key, explains Catherine Ramsdale, a coauthor of the research and senior vice president of technology at PragmatIC, which designs and produces the flexible chips with Arm. While the materials are new, the idea is to borrow as much as possible from the production process for silicon chips. That way, it’s easier to produce the chips en masse and hold down costs. Ramsdale says these chips might cost about one-tenth as much as comparable silicon chips, because of the cheap plastic and reduced equipment needs. It’s, yes, a “pragmatic” way of going about things, she says.
Eric Pop, a materials scientist at Stanford University who wasn’t involved with the research, says he’s impressed with the complexity of the chip and the sheer number of transistors it contains. “This pushes the technology forward,” he says. But pragmatism has limits. The clearest one is how much energy the device uses. The chip consumes 21 milliwatts of power, but only 1 percent of that goes toward performing computations; the rest is wasted as the chip sits idle. That could be produced by a solar cell smaller than a postage stamp outdoors, he explains—in other words, it’s not much—but it’s not a great starting point for efficiency as flexible chips become more complex. “What are you going to do, hook yourself up to a giant battery?” Pop asks.
Myers says the plan for these small chips is to use wireless charging with technology similar to what’s used to pay with a smartphone. But he acknowledges that the chip needs to be more energy-efficient—and he believes it can be, up to a point. The current design can be made smaller, more efficient, perhaps enough to scale to 100,000 gates, he says. But that’s likely the limit. The reason is its rather simple design. Transistors come in two flavors, called “n” and “p.” They complement each other. One turns on when a voltage is supplied and off when it isn’t; the other type does the opposite. “You really want to have both of them,” Pop says. One reason the Arm chip leaks so much energy is that it has only the n type. P-type transistors are more difficult to engineer using the materials Arm and PragmatIC have chosen.
One option for scaling would be to turn to other flexible materials, such as carbon nanotubes, for which it’s easier to manufacture both types. Another option, which Pop’s lab is investigating, is reducing the size and power demands of the transistors by using two-dimensional materials that are made on a rigid substrate and then transferred to a flexible material. The trade-off in both cases is likely to be higher manufacturing costs.
Subhasish Mitra, a computer scientist at Stanford who led the first demonstration of a carbon nanotube computer in 2013, says that while Arm’s design does not appear to demonstrate any theoretical breakthroughs, the researchers appear to have produced a device that’s relatively easy to manufacture and usable for practical applications. “Time will tell how application developers will make use of this,” Mitra says. “I think that’s what the exciting part of this is.”
Which flexible materials ultimately make sense will depend on how a chip needs to be used, Pop explains. Silicon, for example, wasn’t always destined to be at the heart of our devices. For a time, scientists thought that would be germanium—an element that’s a superior semiconductor to silicon. But it isn’t called “Germanium Valley.” Silicon turned out to be easier to obtain and, in some respects, easier to engineer. Cheap, flexible chips are at their own early stage. Will we want the recyclability of paper-based electronics? The potential power and scale of carbon nanotubes? Or maybe we’ll just need the practicality of plastic.