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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

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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

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Dr. Diane Lançon (Mesoscopic Systems, PSI)

Geometrically frustrated lattices such as the 2D Shastry-Sutherland lattice are known to induce emergent quantum phenomena such as spin liquids, topologically protected states, and complex magnetic order. The spin liquid SrCu2(BO3)2 is a famous example of the physical realisation of the Shastry-Sutherland lattice in an insulator [1], yet there exists a family of rare-earth metal tetraborides that exhibit both lattice-induced geometrical frustration and itinerant behavior [2]. In this context, the magnetic order in the frustrated magnet TmB4 is of particular interest. Through measurements of neutron diffuse magnetic scattering, neutron diffraction experiments and resonant soft Xray scattering, we have demonstrated the co-existence of magnetic order with Q-dependent short-ranged correlations in TmB4 and established the evolution of the unconventional magnetic ordering as a function of temperature and applied field.

[1] M. E. Zayed et al., Nature Physics 13, 962966 (2017)
[2] Linda Ye et al., Phys. Rev. B 95, 174405 (2017)

Overview D-MATL Seminar 2018

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Prof. Dr. Janos Vörös (D-ITET)

Embedding metal nanowires into elastomeric materials not only enables a new class of stretchable electronic devices with up to 500% stretchability, or strain sensors with Gauge factors of over 100 but it also brings interesting material science questions and challenges.1
A simple fabrication method has been developed to produce various opto-electronic components using wax-pattern assisted filtration.2 The resulting devices are soft and can be made of biocompatible materials therefore they are also ideal for in vivo applications. For example, electrode arrays made of such composites can be used to stimulate and record from the brain.3 In addition, passive strain sensors can be created to wirelessly measure the filing level of the bladder in handicapped users.4

[1] Stretchable silver nanowire-elastomer composite microelectrodes with tailored electrical properties V. Martinez, et al., ACS Applied Materials & Interfaces, 7 (24):13467–13475. 2015.
[2] Fast and efficient fabrication of intrinsically stretchable multilayer circuit boards by wax pattern assisted filtration; K. Tybrandt , et al; Small 12(2), 180-184, 2016
[3 ]High‐Density Stretchable Electrode Grids for Chronic Neural Recording; K. Tybrandt, et al.; Advanced Materials, 2018. DOI: 10.1002/adma.201706520
[4] Soft Electronic Strain Sensor with Chipless Wireless Readout: Toward Real‐Time Monitoring of Bladder Volume; F. Stauffer, et al.; Advanced Materials Technologies, 2018. doi.org/10.1002/admt.201800031

Overview D-MATL Seminar 2018

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Dr. Stephan Gerstl (ScopeM and LMPT)

Come take a trip into nanostructural analysis capability by taking materials apart atom-by-atom. Atomic scale processes define the properties we witness at macroscales. Therefore we ultimately should characterize our materials near atomic scale to understand and improve them.  Combining high chemical sensitivity and 3-dimensional spatial resolution, atom probe tomography strives for this ideal characterization goal of identifying atoms in their place.  I will show how this is possible with research examples of alloys strengthened by their nanoclusters, semiconductor dopants’ influence, to diffusion zones in minerals. With the latest developments in the field of atom probe tomography, there are opportunities to open the characterization space for softer and even fluid based materials.

Overview D-MATL Seminar 2018

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Dr. Alla Sologubenko

Metallurgy, engineering, material science critically rely on the knowledge of the microstructure – property interrelationships in a material. Assessment of the required microstructural state of the material is the starting point of the complex process of material design and is the backbone of any nanotechnological development. Structural and functional materials being developed by research groups of our Department are designed to exhibit novel and improved physical, chemical and biological properties on micro- and nano-scales. They must fulfill narrow performance criteria and therefore have to possess a well-tuned and stable microstructural state in a broad range of external conditions. Since the understanding of the underlying principles governing the microstructure stability and evolution is the key to the microstructure control, the complex and reliable microstructure analyses of the materials are very important at all stages of the design.
Electron microscopy, especially transmission electron microscopy, presents the most powerful tool for the complex microstructure studies. It is the only technique that enables the direct correlation of the structure information obtained by electron diffraction analyses, the whole range of coherent and incoherent imaging modes using parallel (TEM) and conical (STEM) illuminations and the atomic resolution analytical studies employing energy-dispersive X-ray and electron energy loss spectroscopies at the same area of the specimen and down to sub-Angstrom resolution employing state-of-the-art aberration correctors. Moreover, in-situ TEM techniques allow direct studying the effects of a specific environment on the material stability and performance.
Scientific Center for Optical and Electron Microscopy maintains a number of TEMs and SEMs, including cryo-, high-resolution analytical and state-of-the-art aberration corrected instruments for a wide user base. ScopeM as a highly qualified technical and scientific collective supports interdisciplinary research, encourages scientific collaborations, administers training programs providing a user hands-on experience supported by solid physical understanding of a TEM as a tool.

Overview D-MATL Seminar 2018

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Dr. Alessandro Lauria

Several properties of nanomaterials are related to their crystallinity, size and composition. Many of these structural parameters can be pre-determined through chemical choices operated during their synthesis. I will discuss some of the chemical parameters which enable control over optical properties of nanoparticles, as well as on their further processing toward optical materials at the macroscale.

Overview D-MATL Seminar 2018

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Prof. Dr. Thomas Lippert

Thin films of organic, polymeric, biological, and inorganic thin films are utilized in many applications, e.g. catalysis, microelectronics, sensors, food industry, tools, optics, decorative coatings, and renewable energy applications, etc.. The preparation of these thin films can be achieved with a variety of tools, ranging e.g. from chemical to physical vapor deposition methods (PVD). One PVD method which is used extensively in research, especially for oxides, but recently also in industry in pulsed laser deposition (PLD). It is noteworthy, that it is often assumed, without further analysis, that the films will have automatically the same composition as the target, which is not really the case. I will show, that all steps and the associated parameter, such as background gas type and pressure, target composition, and substrate type and temperature have a pronounced effect on the PLD process, and therefore on the film composition and properties. The sum of all these effects suggests, that in many cases it can be difficult and time-consuming to find conditions to achieve the desired film composition (properties).

The application of thin films as model systems for renewable energy applications will be briefly shown for two topics, i.e. photocatalysis and ion conduction. Pulsed reactive crossed beam laser ablation (PRCLA), a modification of PLD, is used to obtain oxynitride films. Oxynitrides have gained a lot of attention over the last decade due to their photocatalytic properties using visible light. We utilize photoelectrocatalytic measurements (PEC) to study the oxynitride thin films, mainly LaTiOxNy, where we could show that the crystalline orientation has a pronounced influence on the activity. For ion conductors, we are looking mainly at the influence of strain on oxygen and proton conductivity. We could show, that tensile strain will improve conductivity but not by orders of magnitude as reported elsewhere.

Overview D-MATL Seminar 2018

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Dr. Ahmet Demirörs

External fields are a useful tool to manipulate materials without having contact. I will show two examples of how we used external fields, 1) for achieving bio-inspired composites with control on the orientation and position of the colloidal reinforcing components in the composite, 2) for programmable micro-scale cargo delivery purposes where we used magnetic fields for transport and electric fields for pick up and release of cargo.

Overview D-MATL Seminar 2018

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Dr. Michalis Charilaou

Magnetic materials support our most vital infrastructures e.g. by driving powerful motors, generating electricity in power plants, or sensing. Magnetic-field-based sensing existed long before humanity, specifically in bacteria, and it was based on nanoscopic phenomena that we are just discovering today. In this brief talk, I will show how studying magnetic nanoparticles and their assemblies in bacteria can shed light to the distant past of the planet, how this research enables the development of innovative technologies, e.g. for biomedicine, and how it enables us to obtain a deeper understanding of magnetic phenomena in materials.

Overview D-MATL Seminar 2018