MESA+ University of Twente
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René Houben (promotion date: 27 September 2012)

Equipment for printing of high viscosity liquids and molton metals

Promotion date: 27. September

Promotor: Prof. dr. Frits Dijksman, prof. dr. Detlef Lohse

The common denominator of this thesis is the quest for processing a wider range of materials using inkjet technology. One of the limiting factors in commercial available systems is their range of processable viscosities.

Continuous inkjet can overcome this, by splitting the effort of the droplet creation process. The actuation mechanism is responsible to form the droplets, the supply pressure forces the material through the nozzle and accelerates the fluid.

Applications are widespread. Initially developed for additive manufacturing purposes also new ways of powder production are possible. The monodispersity of the droplet generation process results in a reduced size distribution of the powder. The resulting powder reveals to be different in nature: spherical without air enclosures resulting in high density powders.

Also various metal printing options are promising like pyrolitic metal printing and direct metal printing.

3D layer-wise production systems are possible, combining multiple materials into one single product, even generating gradients in material properties within an industrial product.

How did you come to write this thesis?

I work on the subject of inkjet applications in different areas for about eleven years now, at TNO in Eindhoven. We have considerable expertise, resulting in over twenty-five patents in the field. A selection of these, was picked up in this thesis and scientifically worked out in collaboration with Frits Dijksman of the Physics of Fluids group, led by professor Detlef Lohse.

Is inkjet technology considered to be feasible in commercial settings as yet?

For example, futuristic applications can be expected when applying additive manufacturing techniques using inkjet technology. Products seem possible which are layer-wise built using multiple materials. By mixing these materials even gradients in material properties become a reality, allowing the products to gradually change from one material to another. This is considered as a kind of ‘holy grail’.

Using functional materials, some exciting applications can be thought of. For example when integrating electronics to create customer specific hearing aids, or even on-body sensors and other personalised or customised products.

The continuous inkjet concept can lead to a robust industrial processes. Personally, I believe that continuous inkjet technology has several advantages over commonly used drop-on-demand systems. This technology might solve current reliability issues by taking a different approach. With respect to additive manufacturing from my point of view a different approach of the layout of current systems is needed to break away from rapid prototyping and really evolve towards a manufacturing technology. Moving from batch towards continuous production layouts enabling production speeds needed for industrial application. Popular magazines like The Economist believe this generation of additive manufacturing technologies can herald the third industrial revolution even.

Also important are innovations in powder production systems. Here, as in the above mentioned, viscosity and monodispersity of the created droplets play a decisive role. Currently a powder drying facility is being built at TNO in Eindhoven to explore the opportunities of the process in more detail.

What are your future plans?

Working as an intermediate between an expertise centre like TNO and the University of Twente, I learned to bridge the culture differences. On the one hand application driven research tends to drift away in numerous efforts losing deep and trusted knowledge of the basics involved. On the other hand universities often struggle with patenting the vital components of knowledge contents necessary for successful valorisation. As an advisor of TNO on patenting this technology, I hope to play a decisive part in bringing this technology and its various promising applications to the Dutch market.

What, in your opinion, is important for Mesa+ to stay successful in future?

There is a significant difference between universities and TNO with respect to their view on patenting technology versus publishing about technology. At TNO I learned that companies like to be sure of exclusive use of the most strategic knowledge base. Although when patenting technology is discussed it might lead to researchers not feeling free to share their knowledge to colleagues, so disturbing the fruitful academic atmosphere. Nowadays also academic institutes are getting involved in patents, a necessity for the technology to be adopted by industry. However they should behave with great caution not to change the open and highly constructive environment.