Associate Professor at
DTU Chemical Engineering, Anne Ladegaard Skov, recently defended her doctoral dissertation in which she summarizes five years’ research.
It is 2.00 p.m. About 70 people are assembled in a large meeting room on DTU Lyngby Campus, where Anne Ladegaard Skov is about to defend her doctoral dissertation. In short, it centres on how to imitate the way in which our muscles work with the help of so-called ‘dielectric elastomer transducers’.
To create ‘artificial muscles’ flexible, a micrometre-thin material is placed between two even thinner electrodes. When electricity passes through the electrodes, they create an electric field, causing the flexible material together to contract—and when the power is turned off, the material expands again. In this way, electrical energy can be converted into mechanical energy—or vice versa (hence the word transducer).
Such an artificial muscle can then be used for pumps, valves, robots, actuators, generators, sensors—and for harvesting wave energy. This is the field of research in which Anne is engaged. In most places where we can envisage motion as part of a technology, we can draw inspiration from copying our own muscles, in time saving vast quantities of fuel, such as coal and oil.
2.05 p.m. Anne’s presentation
This is the field of research in which Anne is involved—and the subject of today’s doctoral dissertation defence. She begins with an explanation everyone can understand: The first slide shows Pippi Longstocking carrying her horse above her head. Anne explains that she is going to help her childhood heroine lift ten horses—something even the laymen in the audience can grasp. But she then moves from Pippi Longstocking and the muscle analogy—and our immediate fascination—to a room containing highly specialized research equipment.
Anne has researched extensively into the flexible, rubber-like material fixed between the electrodes, as it is exposed to extreme wear and tear when expanded and contracted millions of times over. Many materials were tested, but Anne finally decided on silicone elastomers.
They are durable, react quickly, and can withstand hot and cold temperatures. They also offer substantial resistance to the electric field, so they require a powerful electric current before they react. Elastomers can be mixed with another substance—‘formulated’—so they change properties. However, this may result in a loss of durability or air bubbles being formed. The process requires minute steps and every detail must be correct.
2.40 p.m. Opponents’ question time
After the 30-minute lecture, it is time for her opponents, Dr Andreas Köllnberger (left) and Professor Herbert R. Shea (rigth), to pose questions. They are also given half an hour each. Both praise Anne for her 360 degree approach and ask about what kind of formulations provide good results.
The doctoral candidate replies that it all depends on what they are to be used for. Titanium dioxide produces good results with generators, but not with actuators—glycerol, on the other hand, may be a potential candidate. But how much? And how? Again, these details are extremely important. Everything you do affects the results and this is something you have to contend with as a researcher, says Anne.
While the field of research is young, commercial interest is high, which explains the tendency to oversell results—something that should be avoided at all costs. On the contrary: If the dielectric elastomers are to prove successful, they must be reliable—and the same can be said of the researchers engaged in this field of research.
However, the field is moving in the right direction. Several businesses are becoming involved and dielectric elastomer transducers are finding their way into consumer products. Inserting them into mobile phones to charge them when they move is one possibility. Sensors for sports technologies is another.
While Pippi still cannot lift ten horses, Anne remains confident. The ‘small’ applications will pave the way for more funding and more research so that the technology can gain wider acceptance and possibly—via the harvesting of wave energy—contribute towards fossil fuel independence.
After nearly two hours, her defence is at an end and Anne can now look forward to having the title doctor technices conferred upon her at the Commemoration Day celebrations on 28 April.
