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Greetings to all our friends,
With this issue, we've decided to start something new: after CRN News, you'll find a brief article explaining a technical aspect of advanced nanotechnology. This month, we'll begin with how scientists "see" things smaller than a wavelength of light, with cutting edge sub-wavelength imaging techniques.
CRN NEWS
Happy Birthday to CRN!
We founded CRN sometime in December 2002. We can't agree on the date; Chris prefers Mike's original email in early December, but Mike thinks we should count from the website going online, which happened around Christmas. Perhaps the most official date would be when World Care agreed to support us in being a non-profit. Anyway, those were all in December, so we're now one year old.
We've done quite a lot in the last year: published numerous papers and commentaries, built a prestigious Board of Advisors, given a presentation to the EPA, been mentioned in US News and World Report, and had articles republished on KurweilAI and in Small Times. This year we're going to be even more energetic and diverse. QUESTION #1: If we started a nano-blog, would you read it? We'd really like to know. Please let us know. Thanks!
The Futurist published a great article written by Mike on nanofactories in its current edition. Small Times immediately reprinted it. And this led to a request from another magazine for an article from him, as well as several newsletter signups.
Last month Chris gave his presentation to the EPA Science Advisory Board. It went very well. Everyone on the panel had only a few minutes to speak, and if you've been reading our newsletters (of course you have!) you know that you can't summarize advanced nanotechnology in six minutes. But he managed to hit most of the highlights. Several people on the Science Advisory Board told him afterward that they appreciated the talk. Chris spent the next day talking with several people in Washington, including a Congressional staffer. All the talks were preliminary, but should lead to good things in the future.
There are now almost three hundred people on our newsletter list. That's pretty good! But we'd like to reach more people. QUESTION #2: Would your friends and co-workers be interested in this newsletter? Why or why not? Could you take a minute and tell us what would inspire you to forward this newsletter to them?
The Drexler/Smalley debate has not generated an obvious shift of opinion one way or the other. It looks like we were over-optimistic about that. Apparently, in many people's perception, Smalley's incorrect statements about enzymes weren't enough to weaken his argument. And Smalley and Drexler both talked past each other — which left each side claiming victory and ignoring the equally loud victory yells from the other side.
In other nano-establishment news, we're eagerly awaiting Howard Lovy's promised article on the 21st Century Nano Act and why molecular manufacturing was deliberately excluded from it. He's promised that once the article comes out, he'll post additional information on his blog (nanobot.blogspot.com/). At CRN, we’re working on our own activist response to this controversy — can’t tell you about it yet, but it’s big, and we should be ready to announce something soon. Stay tuned!
SCIENCE AND TECHNOLOGY — by Chris Phoenix
Sub-wavelength Imaging
Light comes in small chunks called photons, which generally act like waves. When a drop falls into a pool of water, one or more peaks surrounded by troughs move across the surface. It's easy to describe a single wave: the curvy shape between one peak and the next. Multiple waves are just as easy. But what is the meaning of a fractional wave? Chop out a thin slice of a wave and set it moving across the water: it would almost immediately collapse and turn into something else. For most purposes, fractional waves can't exist. So it used to be thought that microscopes and projection systems could not focus on a point smaller than half a wavelength. This was known as the diffraction limit.
There are now more than half a dozen ways to beat the so-called diffraction limit. This means that we can use light to look at smaller features, and also to build smaller things out of light-sensitive materials. And this will be a big help in doing advanced nanotechnology. The wavelength of visible light is hundreds of nanometers, and a single atom is a fraction of one nanometer. The ability to beat the diffraction limit gets us a lot closer to using an incredibly versatile branch of physics—electromagnetic radiation—to access the nanoscale directly.
Here are some ways to overcome the diffraction limit:
There's a chemical that glows if it's hit with one color of light, but if it's also hit with a second color, it doesn't. Since each color has a slightly different wavelength, focusing two color spots on top of each other will create a glowing region smaller than either spot.
There are plastics that harden if hit with two photons at once, but not if hit with a single photon. Since two photons together are much more likely in the center of a focused spot, it's possible to make plastic shapes with features smaller than the spot.
Now this one is really interesting. Remember what we said about a fractional wave collapsing and turning into something else? Not to stretch the analogy too far, but if light hits objects smaller than a wavelength, a lot of fractional waves are created, which immediately turn into “speckles” or “fringes.” You can see the speckles if you shine a laser pointer at a nearby painted (not reflecting!) surface. Well, it turns out that a careful analysis of the speckles can tell you what the light bounced off of—and you don't even need a laser.
A company called “Angstrovision” claims to be doing something similar, though they use lasers. They say they'll soon have a product that can image 4x12x12 nanometer features at three frames per second, with large depth of field, and without sample preparation. And they expect that their product will improve rapidly.
High energy photons have smaller wavelengths, but are hard to work with. But a process called “parametric downconversion” can split a photon into several “entangled” photons of lower energy. Entanglement is spooky physics magic that even we don't fully understand, but it seems that several entangled photons of a certain energy can be focused to a tighter spot than one photon of that energy.
A material's “index of refraction” indicates how much it bends light going through it. A lens has a high index of refraction, while vacuum is lowest. But certain composite materials can have a negative index of refraction. And it turns out that a slab of such material can create a perfect image—not diffraction-limited—of a photon source. This field is advancing fast: last time we looked, they hadn't yet proposed that photonic crystals could display this effect.
A single atom or molecule can be a tiny source of light. That's not new. But if you scan that light source very close to a surface, you can watch very small areas of the surface interact with the “near-field effects.” Near-field effects, by the way, are what's going on while speckles or fringes are being created. And scanning near-field optical microscopy (SNOM, sometimes NSOM) can build a light-generated picture of a surface with only a few nanometers resolution.
Some of these techniques will be more useful than others. As researchers develop more and more ways to access the nano-scale, it will rapidly get easier to build and study nanoscale machines. For links to learn more about all these techniques, visit our website at CRNano.org/newsletter.htm#15
If you have any comments or questions about this brief technical explanation, please email Chris Phoenix, CRN's Director of Research -- cphoenix@CRNano.org -- thanks!
=============
For archived C-R-Newsletters, see www.crnano.org/newsletter.htm
The Center for Responsible Nanotechnology is an affiliate of World Care, an international, non-profit, 501(c)3 organization. All donations to CRN are handled through World Care. The opinions expressed by CRN do not necessarily reflect those of World Care.
To donate to CRN, go to crnano.org/support.htm, click on "Donate Now", and remember to specify CRN.
With this issue, we've decided to start something new: after CRN News, you'll find a brief article explaining a technical aspect of advanced nanotechnology. This month, we'll begin with how scientists "see" things smaller than a wavelength of light, with cutting edge sub-wavelength imaging techniques.
CRN NEWS
Happy Birthday to CRN!
We founded CRN sometime in December 2002. We can't agree on the date; Chris prefers Mike's original email in early December, but Mike thinks we should count from the website going online, which happened around Christmas. Perhaps the most official date would be when World Care agreed to support us in being a non-profit. Anyway, those were all in December, so we're now one year old.
We've done quite a lot in the last year: published numerous papers and commentaries, built a prestigious Board of Advisors, given a presentation to the EPA, been mentioned in US News and World Report, and had articles republished on KurweilAI and in Small Times. This year we're going to be even more energetic and diverse. QUESTION #1: If we started a nano-blog, would you read it? We'd really like to know. Please let us know. Thanks!
The Futurist published a great article written by Mike on nanofactories in its current edition. Small Times immediately reprinted it. And this led to a request from another magazine for an article from him, as well as several newsletter signups.
Last month Chris gave his presentation to the EPA Science Advisory Board. It went very well. Everyone on the panel had only a few minutes to speak, and if you've been reading our newsletters (of course you have!) you know that you can't summarize advanced nanotechnology in six minutes. But he managed to hit most of the highlights. Several people on the Science Advisory Board told him afterward that they appreciated the talk. Chris spent the next day talking with several people in Washington, including a Congressional staffer. All the talks were preliminary, but should lead to good things in the future.
There are now almost three hundred people on our newsletter list. That's pretty good! But we'd like to reach more people. QUESTION #2: Would your friends and co-workers be interested in this newsletter? Why or why not? Could you take a minute and tell us what would inspire you to forward this newsletter to them?
The Drexler/Smalley debate has not generated an obvious shift of opinion one way or the other. It looks like we were over-optimistic about that. Apparently, in many people's perception, Smalley's incorrect statements about enzymes weren't enough to weaken his argument. And Smalley and Drexler both talked past each other — which left each side claiming victory and ignoring the equally loud victory yells from the other side.
In other nano-establishment news, we're eagerly awaiting Howard Lovy's promised article on the 21st Century Nano Act and why molecular manufacturing was deliberately excluded from it. He's promised that once the article comes out, he'll post additional information on his blog (nanobot.blogspot.com/). At CRN, we’re working on our own activist response to this controversy — can’t tell you about it yet, but it’s big, and we should be ready to announce something soon. Stay tuned!
SCIENCE AND TECHNOLOGY — by Chris Phoenix
Sub-wavelength Imaging
Light comes in small chunks called photons, which generally act like waves. When a drop falls into a pool of water, one or more peaks surrounded by troughs move across the surface. It's easy to describe a single wave: the curvy shape between one peak and the next. Multiple waves are just as easy. But what is the meaning of a fractional wave? Chop out a thin slice of a wave and set it moving across the water: it would almost immediately collapse and turn into something else. For most purposes, fractional waves can't exist. So it used to be thought that microscopes and projection systems could not focus on a point smaller than half a wavelength. This was known as the diffraction limit.
There are now more than half a dozen ways to beat the so-called diffraction limit. This means that we can use light to look at smaller features, and also to build smaller things out of light-sensitive materials. And this will be a big help in doing advanced nanotechnology. The wavelength of visible light is hundreds of nanometers, and a single atom is a fraction of one nanometer. The ability to beat the diffraction limit gets us a lot closer to using an incredibly versatile branch of physics—electromagnetic radiation—to access the nanoscale directly.
Here are some ways to overcome the diffraction limit:
There's a chemical that glows if it's hit with one color of light, but if it's also hit with a second color, it doesn't. Since each color has a slightly different wavelength, focusing two color spots on top of each other will create a glowing region smaller than either spot.
There are plastics that harden if hit with two photons at once, but not if hit with a single photon. Since two photons together are much more likely in the center of a focused spot, it's possible to make plastic shapes with features smaller than the spot.
Now this one is really interesting. Remember what we said about a fractional wave collapsing and turning into something else? Not to stretch the analogy too far, but if light hits objects smaller than a wavelength, a lot of fractional waves are created, which immediately turn into “speckles” or “fringes.” You can see the speckles if you shine a laser pointer at a nearby painted (not reflecting!) surface. Well, it turns out that a careful analysis of the speckles can tell you what the light bounced off of—and you don't even need a laser.
A company called “Angstrovision” claims to be doing something similar, though they use lasers. They say they'll soon have a product that can image 4x12x12 nanometer features at three frames per second, with large depth of field, and without sample preparation. And they expect that their product will improve rapidly.
High energy photons have smaller wavelengths, but are hard to work with. But a process called “parametric downconversion” can split a photon into several “entangled” photons of lower energy. Entanglement is spooky physics magic that even we don't fully understand, but it seems that several entangled photons of a certain energy can be focused to a tighter spot than one photon of that energy.
A material's “index of refraction” indicates how much it bends light going through it. A lens has a high index of refraction, while vacuum is lowest. But certain composite materials can have a negative index of refraction. And it turns out that a slab of such material can create a perfect image—not diffraction-limited—of a photon source. This field is advancing fast: last time we looked, they hadn't yet proposed that photonic crystals could display this effect.
A single atom or molecule can be a tiny source of light. That's not new. But if you scan that light source very close to a surface, you can watch very small areas of the surface interact with the “near-field effects.” Near-field effects, by the way, are what's going on while speckles or fringes are being created. And scanning near-field optical microscopy (SNOM, sometimes NSOM) can build a light-generated picture of a surface with only a few nanometers resolution.
Some of these techniques will be more useful than others. As researchers develop more and more ways to access the nano-scale, it will rapidly get easier to build and study nanoscale machines. For links to learn more about all these techniques, visit our website at CRNano.org/newsletter.htm#15
If you have any comments or questions about this brief technical explanation, please email Chris Phoenix, CRN's Director of Research -- cphoenix@CRNano.org -- thanks!
=============
For archived C-R-Newsletters, see www.crnano.org/newsletter.htm
The Center for Responsible Nanotechnology is an affiliate of World Care, an international, non-profit, 501(c)3 organization. All donations to CRN are handled through World Care. The opinions expressed by CRN do not necessarily reflect those of World Care.
To donate to CRN, go to crnano.org/support.htm, click on "Donate Now", and remember to specify CRN.
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