Nanotechnology: The fantastic use of atoms, one at a time

By Lucy Komisar

LaBAULE, France

Man-made muscles that contract like biological ones but that are 100 times stronger, that are so powerful they can inject drugs without a needle.

An external skeleton that conforms to the skin and kicks in when a weak knee or ankle kicks out.

Clothing made of cooling materials that amount to a personal air-conditioning system.

The vibrator in a cell phone.

Ah, the last doesn't seem so extraordinary. But they're all built on the new nanotechnology that is using microscopic inventions to interact with the human body, to transmit information in and out, to give it strength or comfort.

Ian Hunter Courtesy M.I.T.

Lynette Jones Courtesy M.I.T.

Ian Hunter and Lynette Jones, scientists at the Massachusetts Institute of Technology who are also husband and wife, work in nanotechnology, also known as "molecular manufacturing." Nano is Greek for dwarf. This "molecular manufacturing" involves the manipulation of individual atoms. Small is not only sometimes better, it is extraordinary.

Hunter runs the BioInstrumentation Lab at MIT, which builds scientific instruments and nanorobots required to generate objects that are even smaller. Jones works in the field of haptics – it comes from the Greek word haptesthai, to touch – which uses the skin as the receptor for information that can't be delivered to eye or ear. Both systems are part of the revolution of "nanotechnology."

They discussed their work at a recent gathering of Forum 21, an annual conference of Americans and Europeans held in France to talk about the latest in science, politics and culture. The conference was started in 2001 by Paul Weinstein and Abby Hirsch Weinstein, Americans living in Paris. He is president of Rive Droite International Investments and she is a journalist. The Forum met this spring in LaBaule, on the coast of Brittany.

Hunter's lab creates biomimetic materials – things that are like living tissue but are not built out of proteins but conducting polymers. (Biomimetic: Imitating, copying, or learning from nature to make artificial products that mimic the natural ones.) He said, "We're trying to create the building blocks of artificial life forms, new materials with life-like characteristics. We've created muscle-like materials that can contract like muscle but are 100 times stronger than real muscle. We've created the equivalent of neurons that take signals from the brain to cause these artificial muscles to contract, and we've created centers for energy storage."

Out of those materials come structures that imitate human organs. He said, "We've produced simple artificial life forms out of these materials, equivalent to what nature might have produced a couple of thousand million years ago – very primitive life forms made out of these wonderful and bizarre materials. We've produced a reflex loop where we have an artificial muscle, a length sensor, some wires and the equivalent of a spinal neuron acting as a reflexive loop as a simple illustration of something with a primitive life-like capability."

The goal is not simply to produce objects in the traditional way, by creating and assembling parts, but to get the materials to actually grow. The materials are designed using molecular techniques that never existed before. Hunter said, "We're almost at a point where we can conceive of a machine that would start growing these artificial life forms that would have the equivalent of muscles and sensors and other functionality."

Nanowalker Courtesy M.I.T.

The new structures will eventually be built by nanowalkers – small robots that can literally crawl over and manipulate atoms. They can move in increments as small as 10^-11 of a meter, smaller than the size of an atom. Hunter said, "The nanowalker walks around with subatomic precision. We have developed 20 different nanowalkers to do different tasks. One might bring a small amount of chemical from one location to another. Another might do a measurement or extract something. Collectively, they are implementing engineering tasks."

Rather than have components separately manufactured, the new products will be co-fabricated, as are humans and other living systems. Nanotechnology is developing manufacturing techniques to grow intelligent systems in three dimensions out of high molecular weight materials that provide more freedom to design important properties.

For example, Hunter said, "If you look at the motors that contract and generate force, which is what muscle does, if you look across nature, the maximum force used by nature almost doesn't change. Whether you're looking at a shellfish or a horse, there's a particular force that's generated. We've succeeded with artificial materials where we're generating 100 times more force than what nature created. We have invented new molecules; when you activate them with a small voltage they contract and generate gigantic force."

"The artificial muscle we've created is in early stages being used as heart assist material, in early experiments to create artificial bladders, sphincters and recently for a new method of injecting drugs without using a needle. We've got a material that can contract with such enormous force, it can squirt out a drug at high velocity to go straight through the skin without the need for a needle."

He predicted that within the next five years, there will be clothing made of materials that can cool the skin, so you'll wear your air-conditioning system!

Talk of skin moves us to the specialty of Lynette Jones, who deals with haptics, using the skin actively to provide information about the world.

Touch just involves passive contact, she explains. Haptics brings in the element of active exploration of the environment. For example, when you pick up a glass, you have an immediate impression about its compliance and mass. It's a rigid object, it doesn't compress. So you won't try to crush it. You also know the force you need to generate at the fingertips so that the glass doesn't fall from your hand. If you lose some of the sensors in your fingertips from nerve disease or with old age, you have to deliberately increase that force to hold the glass safely.

Jones explained that the skin is a remarkably sophisticated medium, with 12 different sensors that respond to different sorts of inputs. Some respond to contact, others to the acceleration or movement of an object in the hand, or to movement of the hair on the hand. The skin also has receptors that signal cooling, warming and pain. She said, "One of the challenges in haptic displays is to make use of those sensory pathways to present information to the human operator."

A simple demonstration of a haptic display you may use on a daily basis is vibratactile input that comes from a vibrating cell phone.

People may be in situations where they can't see or hear something they are manipulating, or they may have visual and auditory system overload.

Jones explained, "In a lot of applications in space, the military, and medicine, you have a number of things you are monitoring visually; you may have a lot of auditory cues coming in. You have a relatively unused medium of the skin, about 1.8 square meters of it sitting there." She said it seems a waste not to use the large number of neural connections from the skin to the central nervous system.

So displays are built to enable people to interact with computer-generated virtual environments and robotic systems. One of the large growth areas is in medically operated robotic systems, particularly in endoscopic tools, where surgeons working with long end effectors lose the tactile information they get with small hand-held tools. They may be unable to feel the presence of a lump in soft tissue or the viscous forces in the liquid medium they are moving through.

Jones explained, "So we want to present on these tool handles something about the operative environment, about the mechanical properties and materials in that environment."

Courtesy NASA

"We work on displays that are hand-based or torso-based in which you receive information about the environment, as you move through it," she said. "For example if you're a medical resident practicing a surgical procedure, you may thread the catheter through a virtual environment presented on a computer screen. You can feel the contact through a series of actuators in a hand-held display, and you know when you're pushing against the wall of an artery. You may feel the palpations associated with the fact you are near a blood source. You wouldn't see these things visually."

Just what do you put on the tip of an instrument to make the surgeon "feel"?

Hunter said, "If I want to create a tactile display, we have a sheet of material like cloth that has millions and millions of muscle-like activators that contract and vibrate or perturb or manipulate the skin."

Other new medical devices that are wearable have systems that monitor medical cells through the skin, then analyze the data and transmit information if it has diagnostic significance.

Haptics is important also on a much larger scale. Jones said, "In tele-operation, remote operation – you see that in construction on the International Space Station and undersea work – it's important to have mechanical cues in order to control the robots effectively. If you can't see the object you're controlling – the robotic arm – if you have haptic feedback, then you can get a much better understanding of how you are manipulating the object, where it is in space and what it's moving."

One can put displays on the bodies of pilots to provide directional or emergency information. She explained, "If you're a fighter pilot and you want information about personal orientation, we can activate a series of motors on your skin to say 'this is a vertical,' or we can activate them to say 'go left, go right'." The device becomes a private communication source to enable one to keep oriented in an environment in which the sense of orientation is disturbed.

Why does this work? Jones explained, "The skin is extremely sensitive in picking up vibrations and very small irregularities in surface structure. For that it is superior to the eye. If you look at the acuity of the skin, how sensitive it is, it's remarkable that we can detect with the fingertip a 1 to 3 micrometer dot about 500 micrometers wide on a smooth surface. Visually you would see nothing on that glass surface, but if you move your fingertip over it, you can pick up these asperities in the surface. If it's a repeating pattern, so the same dot reappears at various points on the surface, we can get down to the nanometer level. And that is just with the bare skin."

She said, "It's also superior to the eye in terms of its processing of information in time. The best sense for temporal resolution is the ear; that processes information on the order of .01 milliseconds. For the hand it's about 5 milliseconds, for the eye it's about 25 milliseconds."

Perhaps the most extraordinary use will unite Jones' research with Hunter's. She predicts using new materials as actuators for older people who lose range of motion and have weaker muscles. They will wear an exoskeleton that is flexible and conforms to the skin. "So," she said, "when you generate 30 degrees of knee or ankle flexion, it can exaggerate it so you can continue to walk and support your body."

Hunter and Jones are making great small discoveries!

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