Scientists are building the next generation of atomic-sized devices
For decades industrial production relied on long production lines. This is how masses of workers, humans or robots, built big things like cars and planes, and created smaller and more complex devices like medical devices, computers and smartphones.
Now imagine a future in which the assembly of processors and digital memories, of current generators and of artificial tissues and medical devices, takes place on a small scale that cannot be seen with the naked eye and according to a new set of rules. Today there are already products that include nanotechnology, for example: radiation filters containing tiny pieces of titanium dioxide that block ultraviolet radiation or particles used to improve medical imaging. But in the coming years, an important era will begin in which we will move from nanotechnology contained in products to products that are themselves nanotechnology.
Successful production of these essential nanotechnologies will require both a better understanding of the material's behavior at the atomic level, and new production tools and processes.
One approach is bottom-up guided self-assembly, where small units or subunits such as atoms or nano-components (such as nano-tubes) join larger, more massive components. The scientists can also use strands of DNA or natural or artificial molecules as programmable building materials, and precisely assemble devices and motors of molecular size from them. Another very effective technique is roll-to-roll assembly, where tiny devices are printed on continuous rolls of polymeric sheets.
Nano-manufacturing also requires very precise tools. Some of the tools will be chemical catalysts, others will be biological, optical, mechanical or electromagnetic. It must be assumed that in the more distant future, the toolbox of nanoscale manufacturing will also include new molecules and "meta-materials" that will be engineered to have properties that apparently violate the laws of nature, such as a material that reflects light unexpectedly.
Here is an overview of some of the most exciting nanotechnologies on the horizon and how they might be implemented.
Cyborg tissue scaffolds
It is possible that artificial tissues that are integrated at the cellular level and contain electronic components will one day play a "cyborg" role in the human body. Instead of implanting electronic devices in existing organs, it is possible to grow synthetic tissues on a skeleton containing a multitude of electronic nano-sensors. These nanoelectronic scaffolds could be the basis for engineered tissues that would be used to detect and report medical problems. They will be able to connect part of the nervous system to a computer, machines, or another living body. Scientists at Harvard University and the Massachusetts Institute of Technology (MIT) are today building very fine and elastic methyl-nano scaffolds that can interface with a single cell. The researchers say their goal is to merge tissue and electronics until it is difficult to determine where one ends and the other begins.
Tiny memory
The nanometer production promises to provide smaller and stronger electronic components, with dense memory, efficient and cheaper. And it's a good thing, because the day will come when the scientists and engineers will no longer be able to shrink the computer chips and cool the circuits with the semiconductor technology that has been used for several decades to build integrated circuits. One of the ways around the problem is to use the spin of the electron to carry the information in both the memory devices and the processing devices. IBM, Intel and others are developing such "spintronic" memory and processing devices, which will likely be reliable, fast and energy efficient. Many other approaches involve writing and storing data using nanometer magnets. A research team from Cornell University has demonstrated an energy-efficient way to reverse the magnetic polarization of a nano-magnet. This is a step on the way to a miniature version of magnetoresistive direct access memory (MRAM), devices that will be able to store information even without a power supply. The researchers applied a current to a layer of the element tantalum (ta) with a lithographic pattern. The current induced a spin bias strong enough to reverse the polarity of a nearby magnet. To reverse the spin back to its first state all they had to do was apply a current in the opposite direction. With no current at all, the magnet remained as it was and stored the information even when the device was turned off. This research may lead to devices, such as cell phones and laptops, that turn off and on immediately, and do not waste battery time in standby states.
Plastic muscles
Artificial muscles could help people blink, robotic fish to swim and floats to extract energy from the sea. Chemists will soon use branched thread-like nanometer polymers that elongate when heated and contract when cooled and can be used as heart muscle fibers, cell membranes or artificial drug carriers. Researchers from the University of Pennsylvania, led by Virgil Percek, have already demonstrated that it is possible to strengthen these thin polymers until they can carry a ten-cent coin, which is 250 times heavier than the fiber. The main difficulty before bringing the technology to production stages is finding polymeric building blocks that can assemble the themselves in a predictable way, to create large structures, such as heart tissue for example, that will behave like small artificial muscles.
Communication at laser speed
Photonic integrated circuits that transmit information using light should speed up the operation of our ever-smaller electronic devices. But before the photonic devices become a reality, there is still one fundamental problem: there is a limit to their size. The light diffraction barrier does not allow light to be confined to spaces smaller than half its wavelength, but the wavelengths of visible light are 10 to 100 times greater than any nanoelectronic device.
The researchers are trying to overcome these limitations by transmitting the information using a solid-state "plasmon" laser. The plasmon laser consists of a network of semiconductor nanowires and metal wires of similar size. The intersection points of the grid create cubic spaces where the light will be trapped. These gaps can be as small as XNUMX percent of the bypass barrier, which is about the size of a transistor on a computer chip. If the scientists succeed in coaxing the spaces created between the wires to produce tiny laser bursts, it is possible that the way will be paved for very small optical systems that will be placed between these microscopic transistors. This work is being led by Zhang Zhang and his colleagues at the University of California, Berkeley.
Power plants are contagious
Viruses can be used to build nanometer devices to generate electricity. The bacteriophage M13, a virus that attacks bacteria, is particularly suitable for this. The rod-like virus, which is about 7 nanometers in diameter and about 900 nanometers long, converts mechanical energy into electrical energy (and vice versa). In experiments conducted by biological engineer Sung-Wook Lee from the University of California at Berkeley and his team, a virus was used to assemble a piezoelectric biological material capable of gathering enough electricity to operate a 10 square centimeter LCD screen. This nano-manufacturing approach is based on nature's unique ability to synthesize biological materials within viruses, which can replicate, develop and assemble themselves with atomic precision. The piezoelectric materials based on the viruses will be able to drive nano-sensors and other future medical devices (whether inside the human body or outside it) by utilizing kinetic energy such as the heartbeat for example.
About the author
Michael K. Rocco is a senior advisor for nanotechnology at the National Science Institute of the United States.
