Nanotech lets scientists create "lab-on-a-chip"
_JB:_ This is Earth and Sky, on squeezing the power of a scientific lab into something as tiny as a computer chip.
_DB:_ Experts are calling it lab–on–a–chip. These are miniaturized devices that can analyze chemicals just as in a laboratory. Nongjian Tao is with Arizona State University’s Center for Solid State Electronics. He’s developing these tiny chemical sensors using nanotechnology – the science of the very small.
_Nongjian Tao:_ A molecule is very small, but a molecule is incredibly useful and intelligent, and it can do a lot of things.
_JB:_ When Tao says molecules are “intelligent” he means some molecules already have the property of being able to identify other specific molecules. DNA molecules, for example, do this routinely when they reproduce.
_Nongjian Tao:_ So this means that we can use this property to build a device with chemical sensors that tells you what chemicals you have in the environment.
_DB:_ Lab–on–a–chip has become possible because nanotechnology lets scientists manipulate extremely small materials, on the scale of atoms and molecules. The lab–on–a–chip technology might someday let labs capable of detecting certain kinds of pollution, for example, easily travel to remote or undeveloped areas.
_JB:_ And there may be medical applications – such as monitoring glucose levels in our blood from inside our bodies. If you have questions about nanotechnology, come to earthsky.org. With thanks to the National Science Foundation, we’re Block and Byrd for Earth & Sky.
Emerging lab–on–a–chip technologies are opening up tremendous potential uses, ranging from monitoring glucose levels from within one’s bloodstream, to instant detection of outdoor pollutants such as lead or arsenic in water, to full diagnostic blood work tests from a coin–sized device available in a remote village of the developing world.
Nongjian Tao heads a full–sized laboratory at Arizona State University, where his team, among many others in the world, are tackling the very huge problems involved with manipulating materials at the smallest scales imaginable. Tao spoke to Earth & Sky’s Jorge Salazar about lab–on–a–chip technology.
Salazar: What are some of the things you’re developing in the lab right now?
Tao: Basically, it relies on the recent development of nanofabrication, nanostructured materials. So one of the things that you probably have heard of already is nanotechnology, or nanoscience. The basic idea is that by decreasing the size of the materials or devices, you gain a lot of things. First of all, you gain new properties. Material tends to behave in different ways if you decrease the size. And you also get higher density. Basically, you can pack more devices, or elements of devices, into a smaller area, and that makes the device run smaller and better. So that’s the general concept. Now in particular cases, in my lab, we’re trying to develop chemical sensors using the nanotechnology. So one of the things that we do is we try to wire individual molecules into an electrical circuit. A molecule is very small, but a molecule is incredibly useful and intelligent, and it can do a lot of things. You can think about DNA and proteins, but also think about other organic molecules as well. So one of the things that molecules can do that current silicon–based technology cannot do is, a molecule can recognize other molecules by very specific interactions or binding process. So this means that we can use this property to build a device with chemical sensors that tells you what chemicals you have in the environment. So that’s a general concept here – basically grab a molecule and wire this molecule into an electrical circuit. So now when this molecule interacts, or binds, or recognizes other molecules, to make it simple here, then you can detect the change, or the recognition event by detecting an electrical current.
Salazar: And how is this useful?
Tao: There are many applications. First of all, it can be used for environmental protection. For example, you can design a chip that can detect heavy metal ions such as lead or arsenic in water, and clearly this would be useful for monitoring pollution problems. A similar concept can be applied to monitoring toxic materials in air. And of course, there’s been a lot of interest over the years in homeland security, trying to detect explosive materials or other nasty materials in the air. So the general concept can also be applied to those situations. And, another thing is the biomedical applications that have been an interesting topic for many, many years already, in clinical situations that require one to identify a particular virus, for example. So how can you do that? There are different ways to do that. One way you can do that is by using the chips I described to you – basically you have a lot of molecules with different functions, and they are wired into an electrical circuit, and when this molecule finds, or recognizes virus, you can detect such an event by measuring an electrical signal.
Salazar: It all sounds pretty simple, or is it?
Tao: Well, this is actually very hard, in the sense that usually that molecule is very small. For a large molecule, like proteins, it’s a few nanometers across. And the reason is related to nanotechnology. So that’s the tough part – how to wire molecules in a circuit, because molecules are too small. The smallest a wire can get, if you work really hard, the smallest a wire can get is in the nanometer–scale. So that’s one requirement, that the electrical wiring part has to be very small. And that’s why a lot of people have spent a lot of time, probably over ten years, trying to figure out how to wire molecules into and electrical circuit.
Salazar: So how are things coming along in the development? Are we going to see these devices anytime soon?
Tao: Right now, we have done a lot of tests in the lab, and we have demonstrated a method to fabricate these kind of chips, and we have demonstrated the function of these kinds of chips in terms of detecting certain chemicals. And right now we are also working with Motorola labs to push this into real applications. And one of the things that we do with Motorola labs is to include wireless communications, too. So you have chips that also send signals out, and also take signals from the outside world. So to simplify the answers, we have tests in the labs, basically we try to look at a truly integrated device, so we demonstrate the individual components, and that seemed to work fine in the lab – but in the real world we have to put everything together, to build an integrated device to see how that works at that level.
So it’s still being developed – in a sense it’s not commercially available yet. One of the things, from an application point–of–view, is that you have something that can do a lot of things. You have to focus on a particular thing, I guess, and that means that you have to think about the market and everything. So, we are, at academic labs, we have to focus on the fundamental aspects that demonstrate what is possible, what is not possible, and trying to learn the lessons from all the mistakes, and so on.
Our thanks to:
N.J. Tao
Arizona State University
Professor
Electrical Engineering Department
affiliated with the
Chemistry and Biochemistry Department
Center for Solid State Electronics
