Category Uncategorized

Rachel Grange (D-PHYS)

Nonlinear optics is present in our daily life with many applications, e.g. light sources for microsurgery or green laser pointer. All of them use bulk materials such as glass fibres or crystals. Generating nonlinear effects from materials at the nanoscale can expand the applications to biology as imaging markers or sensors, and to optoelectronic integrated devices. However, nonlinear signals scale with the volume of a material. Therefore, finding nanostructured materials with high nonlinearities to avoid using high power and large interaction length is challenging. Here I will show several strategies to maximize nonlinear optical signals in nano-oxides with noncentrosymmetric crystalline structure and semiconductors. I will demonstrate how we enhance second-harmonic generation (SHG) by using the scattering properties of individual barium titanate (BaTiO₃) nanoparticles, and AlGaAs standing nanodisks. Our results suggest that a strong increase of the SHG signal can be obtained without using plasmonics or hybrid nanostructures.

Then, I will present innovative fabrication approaches of metal-oxides materials that are very different from standard semiconductors or metals. First, solution-processing of nano-oxides may solve, at the same time, the low nonlinear signal and the low throughput of photonic crystal cavity fabrication to obtain cost-effective disposable devices. Our recent results show that the easy fabrication of nonlinear 3D woodpile photonic crystal is possible with solutions of BaTiO₃ nanoparticles. Besides chemically synthesized nanostructures, we developed lithography processes to obtain lithium niobate (LiNbO₃) nanowaveguides, or BaTiO₃ metasurfaces.

Overview Materials Colloquium 2019

Silke Schön (FIRST Lab)

Today, micro- and nanofabrication is not only dedicated to semiconductor devices anymore. Besides laser diodes and transistors, microfluidic devices are used as microarrays for DNA studies or to investigate microorganisms in waste water. Micropatterned structures allow to explore a full range of new applications in engineering, physics, chemistry and biotechnology, e.g. as electrode arrays interfacing with brain cells. This talk will review the most important technologies to fabricate micro- and nanostructures for various applications and demonstrate examples fabricated in FIRST Lab.

Overview D-MATL Seminar 2019

Celestino Padeste (PSI)

Photon sources such as synchrotrons and X-ray free electron lasers (XFELs) offer great opportunities for the material sciences. I will present some examples from the field of polymer technology including our work on lithographic polymer grafting, which relies on the unique capabilities of the EUV-interference lithography beamline at the Swiss Light Source to produce functional polymer nanostructures on polymer substrates. In addition, I will report on our recent developments of polymer supports for serial protein crystallography at XFELs.

Overview D-MATL Seminar 2019

Henning Galinski (Laboratory for Nanometallurgy, D-MATL)

Today, optical metamaterials and metasurfaces are produced using lithography techniques and typically cannot be scaled above the gram level. In addition, the optical response of metamaterials is often designed for a specific polarization, which makes them unsuitable for many real-world applications using unpolarized light.

Here, I will discuss two new approaches to design scalable but disordered metamaterials, whose properties go beyond the effective medium limit. I will chart a course how these two approaches can be used in real world applications, e.g. for energy conversion.

Overview Materials Colloquium 2019

Francesco Stellacci (EPFL)

The vast majority of biological molecules (proteins, lipids, etc.) are amphiphilic, indeed often their water interface presents hydrophobic and hydrophilic patches coexisting at a molecular scale. In light of this observation, in my talk, I will show how amphiphilic nanomaterials (nanoparticles and macromolecules) can establish a series of unique interactions with biological materials, Particular attention will be dedicated to discussing the role and the nature of hydrophobic interaction, highlighting what we do and do not understand about them.

Overview D-MATL Seminar 2019

Dr. Thomas Weber (D-MATL X-Ray Service Platform)

The D-MATL X-ray platform supports D-MATL members (and also external users) with problems that can be solved with X-ray diffraction methods or, more generally, with any problems that are related to crystallography. For an overview about the available infrastructure and services provided see www.xray.mat.ethz.ch. Most of the service requests concern standard problems that require limited user support for data collection or evaluation. However, in my presentation I will talk about two long-term research projects I did together with D-MATL groups. The first is a collaboration with the Spaldin group about the thermoelectric compound PbTe, which has some interesting physical properties. By combining ab-initio molecular dynamics simulation methods and experimental information from X-ray diffuse scattering we succeeded in resolving a controversial discussion in literature about the structural origin of the physical effects. The second part of my presentation will address a joint project with the Schlüter group regarding the structural characterisation of two-dimensional polymers. In the single-crystal-to-single-crystal polymerisation approach it is straightforward to monitor the average conversion from the monomer to the polymer. However, standard methods do not allow the identification of the local polymerisation mechanisms, e.g. how polymerisation propagates through the crystal and which structural properties are crucial for compensating unavoidable local strain in the intermediate states. Some of these questions could be answered with the help of Bragg and diffuse X-ray scattering.

Overview D-MATL Seminar 2018

 

Prof. Dr. Sotiris Pratsinis (D-MAVT)

Flame synthesis of ceramic oxide films as highly selective gas sensors for breath analysis of acetone (e.g. tracer for lipolysis) and NH₃ (e.g. tracer for the treatment of end stage renal disease) will be presented. The performance  of such sensors for monitoring body fat burning during gym work-out will be demonstrated. Sensing at ppb of the far more challenging breath isoprene by pre-separation will be discussed as time permits.

Overview D-MATL Seminar 2018

Prof. Dr. Ingo Burgert (D-BAUG)

Wood possesses a porous hierarchical structure with excellent mechanical properties, which makes it an eligible scaffold to develop sophisticated high performance composites and hybrid materials. Modification and functionalization treatments can be conducted to improve wood properties for traditional fields of application or to add new functions for novel material profiles. Additionally, the natural wood can be delignified to produce porous cellulose scaffolds, while retaining the sophisticated hierarchical structure and the beneficial fibre directionality. The presentation will cover various approaches to develop bio-inspired wood materials, including the utilization of wood-water interactions for actuating wood elements and the fabrication of delignified cellulose scaffolds with excellent mechanical properties. A specific focus will be laid on discussing wood functionalization in a top-down approach as a manufacturing alternative to bottom-up assembly strategies.

Overview D-MATL Seminar 2018

Dr. Edmondo Benetti (Surface Science and Technology)

The application of distinctive polymer topologies, beyond the simple linear chain, to yield cyclic and loops-forming surface-grafted assemblies, enables a broad modulation of highly relevant, interfacial physicochemical properties. This is especially valid on flat surfaces, where the ultra-dense and highly compact character of cyclic polymer “brushes” provide an enhanced steric stabilization of the interface and a superlubricious behavior [1]. Alternatively, when cyclic brushes form shells on inorganic nanoparticles (NPs), their extraordinary structural properties make them impenetrable and long-lasting shields, which extend the stability of NP dispersions and hinder any interaction with serum proteins [2].

Polymer topology effects, typically observed in bulk or in solution are amplified by adding an additional boundary such as a grafting surface. Their precise tuning translates into materials with unprecedented properties and extremely high applicability.

Figure 1 The application of cyclic polymer shells on inorganic NPs provides enhanced stability and biopassivity to the colloids if compared to liner polymer analogues.

References
[1] G. Morgese, L. Trachsel, M. Romio, M. Divandari, S.N. Ramakrishna, E.M. Benetti Angew. Chem., Int. Ed. 2016, 55, 15583-15588.
[2] G. Morgese, B.S. Shaghasemi, V. Causin, M. Zenobi-Wong, S.N. Ramakrishna, E. Reimhult, E.M. Benetti Angew. Chem., Int. Ed. 2017, 56, 4507-4511.

Overview D-MATL Seminar 2018

Prof. Dr. Andreas Stemmer (D-MAVT)

Atomic force microscopy (AFM) has seen a remarkable development – starting from a kind of small sample scanning profilometer in 1986 it gradually evolved into a non-contact imaging tool capable of visualizing chemical bonds in single molecules today. Yet, such superb resolution is not achieved when imaging organic thin films like 2D-polymers. In my talk I will shed some light on practical aspects and requirements of high-resolution imaging. I will further show how the atomic force microscope allows one to image and analyse electronic properties of active nanoscale structures and how a single AFM tip may substitute for complicated four-point probe measurements.

Overview D-MATL Seminar 2018