|Big nanotech: building a new world with atomic precision|
|Monday, 21 October 2013 16:28|
Suppose we could build everything that today's industry can, more cleanly and efficiently, starting with materials as common as sand and carbon dioxide. Cars, aircraft, computers, photovoltaics – all these and much more would be within the scope of this new mode of production, and at low cost.
As I suggested in my introductory article, the principles of physics and engineering show that all this is possible. The key is a prospective technology called high-throughput atomically precise manufacturing, or APM. It is not available yet, but there is a development path in sight that could make it happen.
APM has implications for everything from medicine to economic development to climate change, and the prospect of APM-level technologies poses two basic questions for science and engineering:
• How would APM-level production machinery work?
• How can we develop the technology needed to build it?
APM is based on mundane principles of physics and chemistry (as well as materials science, thermodynamics, statistical mechanics, reaction kinetics, machine kinematics … ). Every detail of APM systems can be designed within the bounds of textbook science, and every aspect of the engineering, taken step by step, is readily understandable.
Indeed, it turns out that APM machinery naturally resembles ordinary factory machinery, because the task of moving parts and putting them together is essentially the same whether the parts and machines are measured in centimetres or nanometres. Similar motions call for similar machines – form follows function.
As for developing the technology needed to build the necessary machinery, there's a long path ahead, yet there has been enormous progress in key areas of atomically precise fabrication. It seems that the greatest challenges will be human, not technical. They are not problems of basic science but of culture, institutions, research focus and conceptual clarity.
A key part of the necessary conceptual clarity is to acknowledge the surprising progress to date, and to recognise that (oddly) much of this progress isn't labelled "nanotechnology".
The key advances toward atomically precise manufacturing will be based on atomically precise structures – structures built with every atom bonded in place according to a plan – and chemists and their colleagues in the molecular sciences have been at the forefront of this technology for more than a century. Everyday products already manufactured using this technology range from pharmaceuticals to the engineered enzymes found in laundry detergents.
When you see a picture of a specific molecule, you're looking at an atomically precise structure. Chemists started drawing and building these structures as far back as the late 1800s. The history of atomically precise fabrication began with structures in the dozen-atom range, and today has reached the range of millions of atoms. And these molecular techniques can not only build structures that comprise millions of precisely arranged atoms, they routinely produce these structures by the billions in beakers of water. The challenge isn't making them, which could be done in a kitchen, but checking that the products came out right, which requires nano-resolution microscopy.
Although these million-atom structures are made of a soft material, researchers have also learned to design and build nanoscale objects of sturdier stuff, a dense polymeric material that can be as stiff and strong as the plastics used to make a computer case. What's more, these thousand-atom parts can be designed to fit together to make larger objects, and can be joined to the million-atom frameworks I mentioned above. One of the most promising applications is to use the large frameworks as circuit boards that provide unique sockets for arrays of different kinds of electronic components.
Nanotechnology by any other name
From the point of view of public understanding, however, there's a problem with these technologies. The million-atom technology builds structures by using segments of DNA double helix as rods, linking the segments together by swapping DNA strands between one another. But DNA makes almost everyone think of genes, not rods linked to from sheets, boxes, or three dimensional structures that resemble the products of a 3D printer. In our system, these would match up and self-assemble in water.
This million-atom-scale fabrication method is called "structural DNA nanotechnology", but the method used to build the thousand-atom structures isn't called nanotechnology at all: it's called "protein engineering". But "protein" makes people think of soft, soggy stuff like meat, while protein molecules in themselves can be strong and hard. The horn of a bull is built of protein – it's a piece of keratin – and woe to the matador who mistakes a horn for a mere piece of meat.
An open road to APM
In atomically precise fabrication, the challenge is to build larger structures, to extend the range of materials, and to make a wider range of functional devices.
Many devices can be built using no more than today's atomically precise materials – biological systems show, for example, that biomolecular components can form motors like the ones that enable bacteria to swim and people to walk, as well as tubes, pumps, sensors, and even programmable manufacturing machines (the ribosomes in your cells that build proteins, directed by data that is transcribed from genes).
In my first paper on nanotechnology I outlined a road to APM, and this road leads through the atomically precise molecular technologies that have emerged in the years since then. We've come along way, but there's a long way to go.
Nanomechanical systems will someday shuffle molecules in desktop factories, much as nanoelectronic systems in desktop computers now shuffle bits. Systems like these will require complex arrays of simple devices of kinds that cannot be built with today's techniques, but can be built with tomorrow's.
APM-level technologies will emerge, sooner or later, whether in the west, or the east, or through a co-operative global effort of the sort seen in so many areas of science today. Progress in atomically precise fabrication has a deep history and every step has brought rewards in areas that range from scientific knowledge to applications in industry and medicine. Progress continues today, driven forward by scientific curiosity, by ongoing rewards, and by the promise of a profound technological revolution.
• Eric Drexler, often called "the father of nanotechnology", is currently at Oxford with the Programme on the Impacts of Future Technology. His latest book Radical Abundance: How a Revolution in Nanotechnology Will Change Civilization was published in May
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