What shall we make today?

Photo: Rune Petter Ness

In Walt Disney cartoons, characters mix chemicals
to make fantastic machines and materials. Today this has become a reality: scientists are designing materials for the future at the atomic level.

By Åse Dragland

Three young scientists are standing in front of a vacuum chamber in a labora-tory at NTNU. Thomas Tybell measures the temperature with an optical thermometer, while behind him, Turid Worren and Kjersti Midtbø follow the measurement with close interest. These SINTEF and NTNU scientists are in the process of creating materials in the form of thin films, and at this very moment a new layer is being deposited in the chamber. With the aid of an ionized gas, Tybell is bombarding his source material with ions; and a new film is created, one layer at a time, as the ions knock atoms off the source so that they nucleate on a substrate supporting the film. The thickness of the film is measured in nanometres – millionths of a millimetre.
A few hundred metres away, Mari Ann Einarsrud is busy with her own way of constructing new materials: by mixing different solutions she controls carefully calculated chemical reactions. She can also influence her “preparations” by adjusting the temperature, pH, or by means of additives.
“I can make films just a few nanometres thick, which I spread out over a surface, but I can also build up three-dimensional structures,” she says. She has been working for several years on building smart materials known as aerogels; transparent and insulating materials for windows, where there is a need for both insulation and light.
The scientists represent a new trend in materials technology, developing new materials whose properties are tailored at the atomic level for particular applications.

Smart materials
We have been building and constructing things from materials for a long time. The purpose of wooden table legs is to keep the table-top off the floor. The concrete structure of an offshore platform is a framework that supports the installations, accommodation and personnel.
The materials of the future will offer us new possibilities. They will be smart and intelligent, with memory and special functions. Thin films – coatings – can be customized to have specific properties such as increased strength, better protection against corrosion or even rejection of graffiti! The scientists simply need to know what properties the films have, and how they are built up at the atomic level in order to be able to exploit their potential.
Developments take place at the nano- and atomic level, and according to Unni Steinsmo, vice-president for research at SINTEF Materials Technology, it will not be long until we are able to create smart materials according to a given recipe.
“The ultimate goal would be if we were able in advance to calculate the properties we wish for, and then arrange the atoms in such a way as to provide the material with just those properties,” says Steinsmo. In fact, her institute is in the process of setting up a laboratory in which scientists will be able to test and study the properties of materials at nanometre level.

Carbon nanotubes are one example of a nanostructure material, and this is what they look like on the inside. The lines indicate the bonds between the carbon atoms that occupy the corners of the hexagons. Photo: pirx.com/Vincent H Crespi.

On virgin ground
Physicists, chemists and computer scientists have had their perceptions revolutionized by nanotechnology. For the past 30 years, demands for an ever greater degree of miniaturization have dominated microelectronics and the IT industry. Sooner or later, the limits of this process will be reached. The smallest elements can not be made any smaller! But scientists realized that they could get round the problem another way. Instead of thinking about reduction and miniaturisation, they could think of building up their components. The clue was to use the tiniest building blocks that we have – atoms.
“Nanotechnology is a partly a matter of manipulating individual atoms or very small groups of atoms. Since a number of different disciplines such as biology, chemistry, physics, and materials science are involved, new principles for interactions and effects arise. These in turn determine how the artificially produced material will function. For example, we can combine inorganic and organic materials to produce new inorganic materials that will not be rejected by the body – such as an artificial hip,” says Steinsmo

Optical functions
Aage Stori is research director at SINTEF Materials Technology. During the past year he has been doing research on a little component that will control the direction of a beam of light.
“This started when the former company OptiSwitch in Horten engaged us to qualify a component from Russia whose materials were unstable and changed in the course of time,” says Stori. “We took on the job, changed the recipe of the material, mixed certain other chemicals into the gel and obtained the properties we were looking for. The soft, flexible sample of material is optically transparent, and when it is inserted between two electrodes, we can change its shape by modifying the electrical field. The response is extremely rapid, and can be used, for example, to change the direction of a beam of light. This enables the unit to be employed as a switch for optical signals or to steer light in a specific direction.”

Materials for microsystems
Turid Worren, also of SINTEF Materials Technology, is member of a project team that operates across departmental boundaries.The team is making functional ceramics, i.e. compounds of metallic and non-metallic elements that end up as highly advanced “ceramics”. At the moment, they are making thin films of a piezoelectric material for microsystem applications
“In a piezoelectric material we can displace positive and negative charges if we hit it with a hammer or deform it by some other means,” says Worren. “One side of the material becomes positively charged while the other becomes negative, which means that we have produced a short-lived electric charge. In some portable computers, this effect is employed to turn on the background lighting in the LCD screen.”
The scientists can also go the other way round. Instead of producing an electric charge, they can apply a voltage to the material and make it expand or contract.
“This can be used to produce mechanical signals, or to make things vibrate or move, such as in medical ultrasonic instruments or small scanners,” says Worren.
The scientists are going to make a small piezoelectric buzzer, which will consist of a silicon beam up to a few millimetres on the side and just a few microns thick. A layer of piezoelectric material and electrodes are deposited on its surface, an ac voltage is applied, and the beam oscillates, producing a sound within the audible frequency range.

Professor Mari Ann Einarsrud at NTNU is working on a ”smart” material known as an aerogel, which is transparent and has good insulating properties. Photo: Rune Petter Ness

Metals with memory
“Peder”, aged 67, was suffering from weakened blood-vessel walls, which meant that a blood vessel near his stomach was ballooning out. In order to prevent it from giving way completely, doctors at St. Olav’s Hospital in Trondheim introduced a 14 cm-long prosthesis into the weakened blood vessel. The “stent” was surrounded by a special metal mesh which was cooled down before the surgical intervention. Once inside the blood vessel, the metal alloy soon rose to body temperature; the mesh expanded, fastened itself to the blood-vessel wall by means of tiny hooks, and reinforced the blood vessel, with the result that “Peder” is completely healthy once again.
The nickel-titanium alloy of the mesh is a “shape memory metal alloy”. The metal shrinks when it is cooled, but “remembers” its original shape, to which it returns when its temperature rises. “Several thousand Europeans have already had alloys of this sort operated into their bodies,” explains Hans Olav Myhre at St. Olav’s Hospital.

When cables form grippers
Materials that return to their original shape can also be used in other fields, such as the petroleum industry. Asbjørn Andersen, a scientist at SINTEF Petroleum Research, felt that alloys of this sort would be perfect for downhole use in oil wells as actuators that would cause valves to open and close. Tests were also done on whether it would be possible to use the concept to fasten cables to the inside of five-kilometre lengths of coiled tubing.
“It would be really smart to put small pieces of memory alloy on the cable and then circulate hot water through the tubing to make the cable swell up and form grippers. The only drawback was that another company already had an alternative technology for this purpose,” says Andersen. Although the product as such came to nothing, the reports from SINTEF Petroleum Research aroused a great deal of interest.

Further developments
Functional materials are by no means a new phenomenon. Mobile telephones, computers, solar panels, fuel cells and waste purification plants all utilize functional materials. The first shape memory metal, which was described in 1932, was a gold-cadmium alloy. Since then, a great deal of work has been put into understanding and developing these alloys for commercial applications. However, it is not until now that people have begun to realize the potential of this area. Nearly all technological development today is in connection with new functional materials – and it is now that the greatest efforts are being made to exploit their potential.
The new ICT materials have the most fantastic names. When the capacity of CDs, MDs, and DVDs quadruples, for example, this is because the laser diode
is based on indium gallium nitride. The conventional reading head on hard disks has been replaced by a head based on materials known as “giant magnetoresistors”, which enable data to be packed more closely. And the increased speed of storage is due to magneto-optical oxides.
“We can develop most things,” says Unni Steinsmo. “Smart materials are likely to play a decisive role in solving the energy and environmental problems that the world is facing. In order to be capable of producing energy from fossil fuels without emitting greenhouse gases, we will need ceramic membranes that are capable of separating oxygen, CO2 and hydrogen at high temperatures. If we want to exploit sunlight, we will need new processes for turning silicon into solar cells. And if the hydrogen economy is to come to pass, we are completely dependent on new materials for pro-ducing, storing, and converting hydrogen. But competence is essential – and that is what we are building up just now.”

Contact: Turid Worren
SINTEF Materials Technology, Dept. of Applied Physics
Tel: +47 73 59 70 46
Email: Turid.Worren@sintef.no

Gemini facts:

• Materials are what we use to make things. For this reason, their properties are critical. Functional materials have properties that can be changed by external factors. They can be used as membranes, catalysts, sensors, etc.

• Nanotechnology deals with the control, manipulation, and construction of materials at atomic and molecular level.

• Norway has realized the necessity of building up its competence in nanotechnology and functional materials. We are behind in the international race, and have done little research on these materials. For this reason, the University of Oslo, the Institute for Energy Research, SINTEF, and NTNU have launched a national cooperation known as FUNMAT. The NANOMAT programme has a budget of NOK 7.8 million this year, and has been promised NOK 25 million a year for the next four years for research on functional materials and nanotechnology. The four institutions are collaborating, drawing up plans, and launching strategic projects in this field of research.

• Laboratories with highly advanced equipment are essential to FUNMAT, and NTNU is planning a synthesis laboratory in collaboration with SINTEF, in order to be able to produce and characterize materials at nano-level. The University of Oslo is setting up a new joint Functional Materials Laboratory, and SINTEF will soon be opening the Norwegian Microtechnology Centre (NMC), which will have laboratories in Trondheim and Oslo.