Extracts from recent PhD theses

At DTU you can get a research education equal to the world’s very best in fields such as mathematics, physics, informatics, chemistry, biotechnology, chemical and biochemical engineering, electrical engineering, communications technology, space science, mechanical engineering, nanotechnology, energy, civil engineering, transport, environmental engineering, food science, veterinary science, and life science.

Below are extract from a selection of recent PhD theses:

June 2019

"Body can act as power supply"

Illustration: Fei Shen

Tiny power supplies for personalized medicine devices that can generate or store their own energy is a promising technology in the monitoring and control of patient conditions. The power supplies—which are a growing field of research—work by means of biological power sources that can produce electrical energy from fuels found in biological fluids—or using biodegradable catalysts such as enzymes or other bio-components.

Fei Shen from DTU Chemistry has developed a new type of biological power source which uses enzymes to convert chemical energy directly into electrical energy—or to store electric charge. The enzymes are connected to electrodes (cathode and anode) on paper of the 2D material graphene, and the ongoing supply of fuel from the body’s own fluids makes it possible to generate electricity.

In addition, Fei Shen has also managed to create a condenser which makes it possible to store energy.

Illustration: Fei Shen.

"New knowledge about intestinal bacteria"

Illustration: Maria Louise Leth

Gut flora, which is made up of billions of micro-organisms in our gut, is very important for our health. One of these is the bacterium Roseburia intestinalis, which produces Butanoic acid and which helps to keep the intestines healthy and the immune system strong. The occurrence of Butanoic acid-producing bacteria is often lower among people with systemic and inflammatory diseases—e.g. diabetes and colon cancer.

Maria Louise Leth from DTU Bioengineering shows how Roseburia intestinalis converts the complex dietary fibres—mannan and xylan—found in grains, fruits and vegetables into Butanoic acid. By giving Roseburia intestinalis specific carbohydrate chains, the bacterium can outperform Bacteriodes ovatus, which does not form Butanoic acid.

Furthermore, in a dietary experiment on mice, her thesis shows that the addition of mannan to the diet can increase the number of beneficial mannan-degrading bacteria—including Roseburia intestinalis. The study can help to develop effective prebiotics, which can be produced from biomass targeted at Butanoic acid-producing intestinal bacteria that can improve people’s health. 

Illustration: Maria Louise Leth

"Better technology for drug delivery"

Photo: Colourbox

The complexity of the human gut is often the reason why medicinal products are not optimally absorbed when taken orally. But as it is very simple, safe, and easy for patients to take their medicine through the mouth, many strategies have been developed over the years to increase the absorption of drugs, so they are best protected through the gastrointestinal system.

Such strategies include microstructures with reservoirs, which ensure a directional release of the drug. But the manufacture of these structures is still complicated and costly.

Lukas Value from DTU Health Tech has developed a method for 3D printing these structures, so that they are simpler, more cost efficient, and provide greater design freedom. At the same time, the release of medication into the body is improved.

Photo: Colourbox

May 2019

"Fish inspire development of new heat exchangers"

Photo: Colourbox

With inspiration from the blood vessels of fish species such as tuna, porbeagle, and gloss fish, Kristina Navickaité from DTU Energy has developed new heat exchangers. Everyday examples of heat exchangers are radiators and the grid on the back of refrigerators.
The blood vessels in the above-mentioned fish act as counter-flow heat exchangers, where hot blood from the heart heats the cold returning blood. These fish are therefore able to maintain a body temperature that is higher than the ambient temperature by virtue of blood vessels whose walls are wavy—but where the hydraulic diameter inside remains the same.

Kristina made prototypes for tubes that mimicked blood vessels and found that the heat transfer and flow resistance was able to provide a 160 per cent higher performance than a straight tube. In connection with magnetic cooling, there was also a clear improvement in the performance output of the heat pumps. At the same time, the design made the system more compact. The project thus shows that heat exchangers can be made smaller while still managing to transfer the same amount of thermal energy.

Photo: Colourbox

"Algorithms for electricity system’s management of electric vehicles"

Photo: Joachim Rode

Creating a stable and socio-economically efficient electricity system based on renewable energy and capable of supporting the widespread distribution of electric cars poses a huge challenge. Such a system must meet a range of different needs, depending on whether they are seen from the point of view of the operators of the transmission system, the TSOs—or from the point of view of the local operators of the distribution network—the DSOs. 

Generally speaking, for TSOs the need is to increase the share of renewable energy—while the DSOs experience negative effects from electric vehicles on the distribution network. This means that a service supplied to one partner may have an undesired effect on another.

Antonio Zecchino from DTU Electrical Engineering has examined how the electric vehicle charging output and stored energy can be used in the electricity system. Among other things, he has developed algorithms that can minimize errors while maximizing the effectiveness of the electric vehicle fleet. This may help to ensure stable and socio-economically sound management of the increasing number of electric vehicles.

Photo: Joachim Rode.

"‘Spiral’ signals can increase internet speed"

Illustration: Colourbox

Optical fibres that support only a single type of light waves are the backbone of our communications infrastructure. However, these fibres have a finite capacity which we are rapidly approaching. Therefore there is a need for new optical fibres and the most promising solution is to use the same fibre to transfer independent data at the same time and on the same wavelength. This may be possible, for example, using wave types which are ‘spiralled’—i.e. that move through the fibre in a spiral-like motion.

Kasper IngerslevK from DTU Fotonik has examined a special optical fibre with an air core that supports stable transmission of ‘spiral’ wave types. The fibre makes it possible to transmit 12 spiral wave types at the same time without the need for signal processing with multiple inputs and outputs.

The complexity of communication systems that make use of this method is typically high, and several research groups around the world are in the process of optimizing the detectors to be able to receive a signal of this type.

Illustration: Colourbox.

January 2019

"Rapid diagnosis of hemolysis"

Illustration: Chen Zhou

Hemolysis - red blood cells that rupture prematurely - is a global health problem. The disorder may have many causes - hereditary being among them. Currently, there is no fast and reliable method to detect hemolysis in clinical practice because the diagnosis requires the separation of red blood cells and blood plasma by means of centrifugation, for example.

Chen Zhou from DTU Nanotech has - among other things - developed a sensor which solves the problem. Using new nanofilters on an optical waveguide it is possible to measure very small blood samples without any further preparation. The nanosensor, which has shown promising results, is integrated in a commercially available analyser from Radiometer Medical Aps.

Illustration: Chen Zhou

"Algorithm can work with compressed data"

Illustration: Colourbox

In line with the exponential increase in data volume, there is a corresponding requirement for data storage, transmission, and processing.  While hardware development - among other things - has supported these needs in the form of more powerful computers and large data centres, it can no longer keep pace.  There is now a need for solutions that can fully exploit the hardwaree.g. by compressing data. However, this is not a simple exercise.

Mikko Berggren Ettienne from DTU Compute has designed algorithms, data structures, and protocols which can work directly with compressed data. Among other things, he has designed a data structure that can determine whether a sentence or a word is part of a larger compressed text without first having to unpack the entire text.

The response time is as fast as if the text were not compressed - and the space requirement will often be significantly lower. This makes it possible to make calculations on larger volumes of data at the same speed as today - and most importantly without increasing hardware requirements.

Illustration: COLOURBOX

"Database of unknown materials"

Illustration: Colourbox

A wealth of applications is expected to come into play,
as large numbers of new 2D materials are discovered. To date, approximately 50 different 2D materials have been produced - graphene being the first and best-known material.

Sten Haastrup from DTU Physics has systematically investigated the properties of more than 3,000 new 2D materials which have not yet been manufactured. By starting with known 2D materials, he has used a computer to systematically replace the atoms of these materials with similar atoms from the periodic table.

This method offers thousands of potential structures. Sten Haastrup has then calculated the stability, resilience, and the thermodynamic, electronic, and optical properties of the materials. The database has subsequently found hundreds of all-new materials - approximately 30 of which have particularly interesting properties. These will now be studied in detail with a view to potential manufacture.

Illustration: Colourbox

Learn much more about our PhD programme.