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Metal nanowires in an elastomer: an interesting composite material for bioelectronics

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

Atom-by-atom tomography

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

Transmission electron microscopy at Hönggerberg or how ScopeM can help you

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

Structure-function relationship in optical nanomaterials

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

Growth of thin films by pulsed laser deposition – fundamentals and applications

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

Electric and magnetic manipulation of colloids for materials and devices

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

Fundamentals and applications of magnetic nanostructures: a 2500-year-old story

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

Amyloid nematic and cholesteric phases

Prof. Dr. Raffaele Mezzenga

Protein Nanofibrils generated from globular proteins by unfolding, hydrolysis and one-dimensional polymerization are colloidal aggregates exhibiting mesoscopic properties comparable to those of natural polyelectrolytes, yet with persistence lengths several orders of magnitude beyond the Debye length. This intrinsic rigidity, together with their chiral, polar and charged nature, provides these systems with some unique colloidal behavior, which share similarities and differences compared to other filamentous colloids. In this talk I will discuss our current understanding on the physical properties of food protein nanofibrils and the implications on their liquid crystalline properties.

Overview D-MATL Seminar 2018

Assessing numerical methods for molecular and particle simulation

Dr. Xiaocheng Shang

I will discuss the design of state-of-the-art numerical methods for molecular dynamics, focusing on the demands of soft matter simulation, where the purposes include sampling and dynamics calculations both in and out of equilibrium. I will also discuss the characteristics of different algorithms, including their essential conservation properties, the convergence of averages, and the accuracy of numerical discretizations.

Overview D-MATL Seminar 2018

The magic and mystery of semiconductor nanoplatelets

Prof. Dr. David J. Norris

Colloidal nanoplatelets are atomically flat, quasi-two-dimensional sheets of semiconductor that can exhibit efficient, spectrally pure fluorescence. Despite intense interest in their properties, the growth mechanism behind their highly anisotropic shape and precise atomic-scale thickness remains unclear, and even counter-intuitive for commonly studied nanoplatelets. Here we will explain how simple growth kinetics can lead to such materials. Knowledge of this previously unknown mechanism for controlling shape at the nanoscale can then lead to broader libraries of quasi-two-dimensional solids.

Overview D-MATL Seminar 2018