Final Report Summary - NANOGOLD (Self-organized nanomaterials for tailored optical and electrical properties)
Eight European universities, coordinated by the Ecole Polytechnique Federal de Lausanne (EPFL), came together in NANOGOLD, a European Union funded project, in order to discover and achieve new metamaterials with properties never observed in nature which belonged rather to the realm of science fiction.
The goal was to develop future materials, or bulk three-dimensional optical metamaterials, which were at the heart of applications that promised to revolutionise various fields of science. A referential example was a material that was part of an imaging device that possessed a resolution which outperformed established microscopes by orders of magnitude. Alternatively, materials were developed that could conceal objects for an external observer and to let it be invisible. Or even further, materials were developed that absorbed completely the light across a large spectral domain. The absorbed light in these materials was converted into heat, which could be used on the nanoscale in, for example, catalytic or thermo-photovoltaic applications. The novelty of our approach was to use methodologies of self assembly to fabricate these metamaterials. This entailed the use of the materials as an ink which could be fabricated cheap, in large quantities, and which could be deposited on arbitrary objects.
The incredible material properties were obtained by incorporating small and resonant entities into a periodic or even amorphous nanoscopic structure. Under different options we identified metal nanoparticles, which were readily available as the most promising entities to achieve a significant interaction of light with matter. Unique to our approach was the assembly of meta-atoms made from a large number of metallic nanoparticles with a well defined geometry to form the composite material. The nanoscopic structure allowed these composites to behave as a homogeneous material with properties largely different from those observed in its constituents. The collective resonance of these nanoinclusions appeared only when a critical number of resonant units were unified, in the same way that a single molecule of water (H2O) was not wet, but many of these molecules formed water.
In this project, research followed an interdisciplinary approach and combined visionary inorganic chemistry, organic synthesis, macromolecular physics of electromagnetic resonance and liquid-crystal technology. The organisation of nanoparticles composing the metamaterials was obtained using the techniques of liquid-crystal molecules which were able to self organise. The advantage of using this technology was that the structural parameters of the material could be controlled by external means, making the material properties adjustable according to various parameters such as temperature, electric field or light.
To obtain a regular structure of the metallic nanoparticles, they were directly introduced into an organic molecule containing mesogenic, i.e. liquid-crystalline, entities. The resulting hybrid molecules self-assembled via intermolecular interaction. After analysis of both the individual components, the 'hybrid molecules' and the material as a whole, theoretical simulation of the optical properties guided the researchers in the most effective direction in terms of material realisation. This reverse engineering approach helped researchers to understand how the materials properties could be modified and enhanced.
Applications for this research were still under discussion, but some immediate areas were already identified. The main idea was to create devices that were transparent for certain wavelengths but not for others. This was already possible to do by the time of the project elaboration, but required the use of complicated multi-interference structures. In this project, the focus was on the development of an ink that could be applied to a surface and would allow to get these functionalities and to create particular effect in a single layer, as a magic paint.
The importance of metamaterial research was shown in the number of initiatives to stimulate the research and was out of question. Despite the impact of the photonic metamaterials for a lot of applications our approach added, in general, particular advantages not accessible by using conventional or advanced nanotechnology. Our project was the first bottom up approach for metamaterial fabrication and boosted technology development in the field. A lot of designs were based on restrictions given by means of nanotechnology fabrication.
Chemistry of nano-composites was a wide field of research. First applications of self organised composite materials with thermotropic properties led to a rush to this material class. The concept could be widened to allow for specific material design for applications like sensing paints. One aspect of materials characterisation like macromolecular assemblies was the development of low resolution crystallography methods for determination of nanostructures of self assembled metamaterials. This was in so far important as the structures dimension did not fit well with classical structural analysis means.
By the time of the reporting period, engineering of nanostructure and microstructure composite materials in the context of optical functionality was rare. Moulding and film processing as well as fibre spinning were used to bring materials into shapes. Bulk materials could be shaped very precisely, for instance with polishing and micromachining. If one considered high resolution of spatial modulated materials only very few results were available that showed optical functionality. The main problem was clustering of nanoparticles, de-mixing and wetting problems. Our material concept was explicitly based on such effects and our material designs would largely contribute to applying fabrication concepts available in this area. In a long run, when materials were designed that could be processed at room temperatures, the whole plastic technology process chain including injection moulding and hot embossing would be available for fabrication. In addition, it was expected that the material would have highly anisotropic electrical conductivity. Such properties could impact device development for organic electronics and solar cells.
The foreground of this project was disseminated in many ways, mainly to the scientific community, but also to the industry through the organisation of two workshops and publications in results' oriented magazines. The main activities were the publications of 51 peer reviewed articles and the participation in many international conferences and workshops were the NANOGOLD members disseminated results obtained during the project through oral presentations or posters. Moreover, two dissemination workshops were organised during the course of this project to share results and expectations with other members of the scientific community and the industry. A flyer, which could be downloaded from the project website, summarised the project strategy and goals.
In 2010 all project partners contributed to the 'Nanostuctured metamaterials: Exchange between experts in electomagnetics and material science' brochure edited by the European Commission (editor in chief Anne F. de Baas, editors Sergei Tretyakov, Philippe Barois, Toralf Scharf, Volodymyr Kruglyak and Iris Bergmair) together with the NIM_NIL, Metachem and Magnomics projects.
In 2012, it was decided to write a project booklet about the achieved exploitable results as a complement of the above mentioned brochure. As this booklet was intended to be distributed at the last dissemination workshop, it was decided to be done in partnership with the other involved projects. Profactor GmbH from the NIM_NIL project took over the responsibility of editing the brochure 'Nanostructured metamaterials: Exploitable results'. The very professional resulting booklet was distributed to all participants of the last dissemination workshop held in Jena, in July 2012.
The book 'Amorphous nanophotonics' was also its final stage by the end of the reporting period. It would be edited by Carsten Rockstuhl (JENA) and Toralf Scharf (EPFL) and would be published by Springer. It was planned to be printed in February 2013 and would be sent to all participants of the dissemination workshop in Jena. This book was co-written by all beneficiaries at the end of the project.
Toralf Scharf (project coordinator, EPFL) was interviewed and published in the European Union's Research Journal (T. Scharf, P. Truss EU Research 2/2012, 50-52). The three pages article 'The building blocks of metamaterials' could be downloaded from 'http://nanogold.epfl.ch'. The hosting journal was the leading non peer-review research journal in Europe. European Union Research was an effective, accessible and widely distributed platform for the dissemination of scientific research.
Furthermore, Toralf Scharf (EPFL), Carsten Rockstuhl, Thomas Bürgi (UNIGE) and Georg Mehl (UHULL) were interviewed for the International Innovation Report, whose 2012 edition focussed specifically on nanotechnology, photonics and electronics research. This journal was an annual research report. The 2012 report would be distributed to over 30 000 stakeholders across all countries in Europe and the International Cooperation (INCO) countries at every level in the government, policy, academic, research and different stakeholder communities in October 2012.
In assition, Alastair Cunningham (UNIGE) was interviewed and published in the December 2011 issue of the Gulf-life magazine. The article 'The invisible men' was available online at 'www.gulf-life.com'.
Press releases were made in the different countries involved in NANOGOLD. Press releases were done in the main language of each country, and were the following:
1. 'La nanotechnologie est-elle le premier pas vers l'invisibilité?', by T. Scharf and J. Lenoble Zwahlen, Flash (EPFL magazine), March 2010
2. A publication by T. Scharf and J. Lenoble Zwahlen, Flash (EPFL magazine), planned for November 2012
3. 'Von künstlichen Materialien zu realen Produkten', by Dr Ute Schönfelder, July 2012, online publication at 'http://idw-online.de/de/news486260'
3. A release by UPAT, in Greek, accessible through the NANOGOLD local news in October 2012
4. A planned press release - service of communication by the University of Geneva in October 2012.
The work carried out for the NANOGOLD project would be included in several PhD theses and diploma theses, which were fully or partially funded by the project. The list of the PhD theses is given below. The titles might change. The forecast date of thesis defence is written in brackets, since some of them were anticipated to be completed beyond the end of the reporting period:
1. Christoph Menzel (JENA), 'Characterisation of optical metamaterials - Effective parameters and beyond', November 2011
2. Xiaobin Mang (USFD), 'Self-assembled liquid crystal nanostructures', January 2012
3. Ruibin Zhang (USFD), 'Hierarchical self-assembled structures of liquid crystals in nano-templates', October 2012
4. Alastair Cunningham (UNIGE), 'Metamaterials by self-assembly of metal nanoparticles' (December 2012)
5. Bai Jia Tang (UHULL), 'The synthesis and investigation of hierachically structured liquid crystal gold nanocomposites' (December 2012)
6. A. J. Ferreira (UHULL), 'The synthesis and investigation of photoactive organic-inorganic nanohybrids' (December 2012)
7. Stefan Mühlig (JENA), 'Self-assembled metamaterials' (Spring 2013)
8. Ugo Cataldi (UNICAL), 'Soft-composite elastomeric microstructures for active plasmonic applications' (October 2013)
9. Vassiliki Kyrimi (UPAT), 'Hybrid layer-multiple-scattering/ discrete-dipole approximation method for the theoretical study of the optical properties of nanostructured metamaterials' (2014)
10. Z. Ahmed (UHULL), 'The investigation of LC nanocomposites incoprating highly birefringent rigid organic groups' (December 2014).
In addition, the list of the diploma or MSc theses is given below:
1. J. Schneider (JENA), 'Active materials integrated in colloidal nanoparticles', July 2011
2. Fabio Cerminara (UNICAL), 'Fabricazione e caratterizzazione di dispositivi plasmonici in materiali soft-elastomerici', May 2012
3. Pierantonio Cerminara (UNICAL), 'Studio e caratterizzazione di trasduttori ottico - elettronici realizzati in matrici elastomeriche', May 2012.
Further information about the project could be obtained at http://nanogold.epfl.ch.
The goal was to develop future materials, or bulk three-dimensional optical metamaterials, which were at the heart of applications that promised to revolutionise various fields of science. A referential example was a material that was part of an imaging device that possessed a resolution which outperformed established microscopes by orders of magnitude. Alternatively, materials were developed that could conceal objects for an external observer and to let it be invisible. Or even further, materials were developed that absorbed completely the light across a large spectral domain. The absorbed light in these materials was converted into heat, which could be used on the nanoscale in, for example, catalytic or thermo-photovoltaic applications. The novelty of our approach was to use methodologies of self assembly to fabricate these metamaterials. This entailed the use of the materials as an ink which could be fabricated cheap, in large quantities, and which could be deposited on arbitrary objects.
The incredible material properties were obtained by incorporating small and resonant entities into a periodic or even amorphous nanoscopic structure. Under different options we identified metal nanoparticles, which were readily available as the most promising entities to achieve a significant interaction of light with matter. Unique to our approach was the assembly of meta-atoms made from a large number of metallic nanoparticles with a well defined geometry to form the composite material. The nanoscopic structure allowed these composites to behave as a homogeneous material with properties largely different from those observed in its constituents. The collective resonance of these nanoinclusions appeared only when a critical number of resonant units were unified, in the same way that a single molecule of water (H2O) was not wet, but many of these molecules formed water.
In this project, research followed an interdisciplinary approach and combined visionary inorganic chemistry, organic synthesis, macromolecular physics of electromagnetic resonance and liquid-crystal technology. The organisation of nanoparticles composing the metamaterials was obtained using the techniques of liquid-crystal molecules which were able to self organise. The advantage of using this technology was that the structural parameters of the material could be controlled by external means, making the material properties adjustable according to various parameters such as temperature, electric field or light.
To obtain a regular structure of the metallic nanoparticles, they were directly introduced into an organic molecule containing mesogenic, i.e. liquid-crystalline, entities. The resulting hybrid molecules self-assembled via intermolecular interaction. After analysis of both the individual components, the 'hybrid molecules' and the material as a whole, theoretical simulation of the optical properties guided the researchers in the most effective direction in terms of material realisation. This reverse engineering approach helped researchers to understand how the materials properties could be modified and enhanced.
Applications for this research were still under discussion, but some immediate areas were already identified. The main idea was to create devices that were transparent for certain wavelengths but not for others. This was already possible to do by the time of the project elaboration, but required the use of complicated multi-interference structures. In this project, the focus was on the development of an ink that could be applied to a surface and would allow to get these functionalities and to create particular effect in a single layer, as a magic paint.
The importance of metamaterial research was shown in the number of initiatives to stimulate the research and was out of question. Despite the impact of the photonic metamaterials for a lot of applications our approach added, in general, particular advantages not accessible by using conventional or advanced nanotechnology. Our project was the first bottom up approach for metamaterial fabrication and boosted technology development in the field. A lot of designs were based on restrictions given by means of nanotechnology fabrication.
Chemistry of nano-composites was a wide field of research. First applications of self organised composite materials with thermotropic properties led to a rush to this material class. The concept could be widened to allow for specific material design for applications like sensing paints. One aspect of materials characterisation like macromolecular assemblies was the development of low resolution crystallography methods for determination of nanostructures of self assembled metamaterials. This was in so far important as the structures dimension did not fit well with classical structural analysis means.
By the time of the reporting period, engineering of nanostructure and microstructure composite materials in the context of optical functionality was rare. Moulding and film processing as well as fibre spinning were used to bring materials into shapes. Bulk materials could be shaped very precisely, for instance with polishing and micromachining. If one considered high resolution of spatial modulated materials only very few results were available that showed optical functionality. The main problem was clustering of nanoparticles, de-mixing and wetting problems. Our material concept was explicitly based on such effects and our material designs would largely contribute to applying fabrication concepts available in this area. In a long run, when materials were designed that could be processed at room temperatures, the whole plastic technology process chain including injection moulding and hot embossing would be available for fabrication. In addition, it was expected that the material would have highly anisotropic electrical conductivity. Such properties could impact device development for organic electronics and solar cells.
The foreground of this project was disseminated in many ways, mainly to the scientific community, but also to the industry through the organisation of two workshops and publications in results' oriented magazines. The main activities were the publications of 51 peer reviewed articles and the participation in many international conferences and workshops were the NANOGOLD members disseminated results obtained during the project through oral presentations or posters. Moreover, two dissemination workshops were organised during the course of this project to share results and expectations with other members of the scientific community and the industry. A flyer, which could be downloaded from the project website, summarised the project strategy and goals.
In 2010 all project partners contributed to the 'Nanostuctured metamaterials: Exchange between experts in electomagnetics and material science' brochure edited by the European Commission (editor in chief Anne F. de Baas, editors Sergei Tretyakov, Philippe Barois, Toralf Scharf, Volodymyr Kruglyak and Iris Bergmair) together with the NIM_NIL, Metachem and Magnomics projects.
In 2012, it was decided to write a project booklet about the achieved exploitable results as a complement of the above mentioned brochure. As this booklet was intended to be distributed at the last dissemination workshop, it was decided to be done in partnership with the other involved projects. Profactor GmbH from the NIM_NIL project took over the responsibility of editing the brochure 'Nanostructured metamaterials: Exploitable results'. The very professional resulting booklet was distributed to all participants of the last dissemination workshop held in Jena, in July 2012.
The book 'Amorphous nanophotonics' was also its final stage by the end of the reporting period. It would be edited by Carsten Rockstuhl (JENA) and Toralf Scharf (EPFL) and would be published by Springer. It was planned to be printed in February 2013 and would be sent to all participants of the dissemination workshop in Jena. This book was co-written by all beneficiaries at the end of the project.
Toralf Scharf (project coordinator, EPFL) was interviewed and published in the European Union's Research Journal (T. Scharf, P. Truss EU Research 2/2012, 50-52). The three pages article 'The building blocks of metamaterials' could be downloaded from 'http://nanogold.epfl.ch'. The hosting journal was the leading non peer-review research journal in Europe. European Union Research was an effective, accessible and widely distributed platform for the dissemination of scientific research.
Furthermore, Toralf Scharf (EPFL), Carsten Rockstuhl, Thomas Bürgi (UNIGE) and Georg Mehl (UHULL) were interviewed for the International Innovation Report, whose 2012 edition focussed specifically on nanotechnology, photonics and electronics research. This journal was an annual research report. The 2012 report would be distributed to over 30 000 stakeholders across all countries in Europe and the International Cooperation (INCO) countries at every level in the government, policy, academic, research and different stakeholder communities in October 2012.
In assition, Alastair Cunningham (UNIGE) was interviewed and published in the December 2011 issue of the Gulf-life magazine. The article 'The invisible men' was available online at 'www.gulf-life.com'.
Press releases were made in the different countries involved in NANOGOLD. Press releases were done in the main language of each country, and were the following:
1. 'La nanotechnologie est-elle le premier pas vers l'invisibilité?', by T. Scharf and J. Lenoble Zwahlen, Flash (EPFL magazine), March 2010
2. A publication by T. Scharf and J. Lenoble Zwahlen, Flash (EPFL magazine), planned for November 2012
3. 'Von künstlichen Materialien zu realen Produkten', by Dr Ute Schönfelder, July 2012, online publication at 'http://idw-online.de/de/news486260'
3. A release by UPAT, in Greek, accessible through the NANOGOLD local news in October 2012
4. A planned press release - service of communication by the University of Geneva in October 2012.
The work carried out for the NANOGOLD project would be included in several PhD theses and diploma theses, which were fully or partially funded by the project. The list of the PhD theses is given below. The titles might change. The forecast date of thesis defence is written in brackets, since some of them were anticipated to be completed beyond the end of the reporting period:
1. Christoph Menzel (JENA), 'Characterisation of optical metamaterials - Effective parameters and beyond', November 2011
2. Xiaobin Mang (USFD), 'Self-assembled liquid crystal nanostructures', January 2012
3. Ruibin Zhang (USFD), 'Hierarchical self-assembled structures of liquid crystals in nano-templates', October 2012
4. Alastair Cunningham (UNIGE), 'Metamaterials by self-assembly of metal nanoparticles' (December 2012)
5. Bai Jia Tang (UHULL), 'The synthesis and investigation of hierachically structured liquid crystal gold nanocomposites' (December 2012)
6. A. J. Ferreira (UHULL), 'The synthesis and investigation of photoactive organic-inorganic nanohybrids' (December 2012)
7. Stefan Mühlig (JENA), 'Self-assembled metamaterials' (Spring 2013)
8. Ugo Cataldi (UNICAL), 'Soft-composite elastomeric microstructures for active plasmonic applications' (October 2013)
9. Vassiliki Kyrimi (UPAT), 'Hybrid layer-multiple-scattering/ discrete-dipole approximation method for the theoretical study of the optical properties of nanostructured metamaterials' (2014)
10. Z. Ahmed (UHULL), 'The investigation of LC nanocomposites incoprating highly birefringent rigid organic groups' (December 2014).
In addition, the list of the diploma or MSc theses is given below:
1. J. Schneider (JENA), 'Active materials integrated in colloidal nanoparticles', July 2011
2. Fabio Cerminara (UNICAL), 'Fabricazione e caratterizzazione di dispositivi plasmonici in materiali soft-elastomerici', May 2012
3. Pierantonio Cerminara (UNICAL), 'Studio e caratterizzazione di trasduttori ottico - elettronici realizzati in matrici elastomeriche', May 2012.
Further information about the project could be obtained at http://nanogold.epfl.ch.