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In-person in HCI G4:

Machine Learning for the Inverse Design of (Meta-)Materials

Dennis M. Kochmann (Mechanics and Materials Lab – D-MAVT)

Multiscale material modeling has two primary goals: (i) understanding and predicant a material’s properties based on its small-scale architecture, and (ii) identifying those small-scale structural features that enable us to control and optimize a material’s properties and performance. Owing to the rise of additive manufacturing, metamaterials (or architected materials) have emerged as a special class of artificial materials with interesting or tunable properties, and as a new playground for computational modeling. While the forward problem (i) has produced many successful modeling techniques across scales, the inverse problem (ii) has remained a challenge: how do we design (meta-)materials with target properties? At the core of this challenge are the abundant design and property spaces, as well as the fact that the map from structure to properties cannot be inverted. Here, we will discuss how in recent years machine learning has offered new opportunities for the inverse design of (meta-)materials through generative models that predict metamaterial architectures with extreme, peculiar, or as-designed mechanical properties

Harnessing Size Effects: Where Nanostructures Meet Additive Manufacturing

Rebecca Gallivan (Laboratory for Nanometallurgy – D-MATL)

Nanostructured materials promise to unlock new functionality that can address modern challenges in electronics, health, and infrastructure. However, to fully hardness the power of size-based effects, we need to develop new methods for designing microstructurally complex and heterogeneous nanostructures. Furthermore, deep fundamental understanding of designed nanoscale materials is critical for bringing these tools to the materials engineers of tomorrow. Using novel nanoscale additive manufacturing and nanomechanical techniques, we will explore new pathways for nanoscale materials design and investigate the emergingmaterials behaviors that arise at the intersection of geometric and microstructural size-effects. Insights will focus on beginning to untangle the intricate roles of processing and microstructure in advancing nanoscale materials performance.

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Zoom: https://ethz.zoom.us/j/61014166756

Low-Dimensional Optoelectronics

Lukas Novotny (Photonics Laboratory – D-ITET)

To co-integrate photonics with electronics the length-scale of optical devices has to be reduced below the wavelength of light. To achieve this goal we interface optical antennas made of noble metals with low-dimensional materials, such as graphene, hexagonal boron-nitride (hBN) and transition-metal dichalcogenides (TMDs). Optical antennas enhance the interaction strength and boost the efficiency of low-dimensional optoelectronic devices.

In this talk I will describe different low-dimensional optoelectronic devices that we recently fabricated and characterized. These include 1) waveguide-integrated photodetectors based on MoTe2, 2) light-emitting devices based on inelastic electron tunneling, and 3) nonlinear phased array antennas for directional photon emission.

Six-axis multi-process additive manufacturing for implantable medical devices

Fergal Coulter (Complex Materials – D-MATL)

The presentation will focus on multi-axis additive manufacturing techniques for fabricating bio-hybrid implantable devices. Example objects are detailed, such as patient-specific prosthetic heart valves [1] and cellular macro-encapsulation devices. The design and fabrication of custom 3D printers and vision system hardware, required for their manufacture is also outlined.

Multi-material objects with unique properties are realised by combining multiple deposition techniques - direct ink writing, spray deposition, micro-jetting and/or thermoplastic pellet extrusion - with laser-based 3D scanning techniques. Examples include inflatable minimum energy structures containing bonded layers with differing levels of stress [2]; living bio-inks printed over the surfaces of complex multi-curved mandrels and selectively permeable membranes that are found to encourage cellular on-growth [3].

[1] Bioinspired Heart Valve Prosthesis Made by Silicone Additive Manufacturing in Matter 2019
[2] Production Techniques for 3D Printed Inflatable Elastomer Structures: Part II in 3DP&AM 2018
[3] Additive Manufacturing of Multi-Scale Porous Soft Tissue Implants That Encourage Vascularization and Tissue Ingrowth. Adv Healthcare Matr. 2021

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Zoom: https://ethz.zoom.us/j/66758737383

Magnetoelectric teleportation

Manfred Fiebig (Multifunctional Ferroic Materials – D-MATL)

Teleportation, the transfer of matter or energy between points in space without traversing the physical distance between them, is a common subject in science fiction. Aside from the fascination in propagation-less transfer of matter or energy, teleportation allows authors or filmmakers to dispose of the description of lengthy journeys or save the costs of depicting these. Teleportation has been realized in the quantum world, where it denotes the immediate transfer of the quantum state of an atom or photon through quantum-mechanical entanglement. In this expanded definition, it is a form of communication rather than spatial transformation, and restricted to atomic dimensions. In the macroscopic world, teleportation is believed to be nonexistent, however. Here I demonstrate that nevertheless, compounds with simultaneous magnetic and electric order, so-called multiferroics, permit a special form of teleportation.

Innovating Medical Materials

Inge K. Herrman (Nanoparticle Systems Engineering Laboratory – D-MAVT)

The well-controlled synthesis of nanoscale materials is arguably one of the most important achievements of material science in the past decades. With the push to simplify biomedical material designs, inorganic nanomaterials have regained interest. Especially metal and metal oxide nanomaterials have attracted significant attention due to the scalability and robustness of their synthesis and their tailorable composition and architecture. In the first part, I will present an approach to unite tissue adhesion, based on nano-bridging, with bioactivity for wound healing applications. Uniting these properties requires control over nanoparticle architecture and freedom of choice in materials. Liquid-feed flame spray pyrolysis (LF-FSP) fulfills these requirements, while offering scalable and sterile synthesis. By utilizing the versatility of LF-FSP, we have united the wound closure properties of bioglass with the anti-inflammatory properties of ceria in one nanoparticle hybrid system. By tailoring the architecture of the hybrid nanoparticles, temporal control of the material bioactivities can be achieved in order to optimally address the different phases of the wound healing cascade. In the second part of my presentation, I will briefly introduce a new adhesion concept based on mutually interpenetrating networks as a new route to high performance tissue adhesion under most demanding conditions, such as the ones encountered in the gastrointestinal tract.

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Materials Colloquium 2020 - December, 2nd, 16:30

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Laura Alvarez (Laboratory for Soft Materials and Interfaces, D-MATL, ETHZ)

Programming the dynamics of artificial microswimmers provides a benchmark towards the realization of smart microscale devices. Motile microorganisms, such as bacteria, have developed sophisticated mechanisms to regulate their dynamics based on environmental changes [1]. The creation of artificial programmable microswimmers capable of reproducing such complex performance using much simpler structures remains an open challenge [2]. Here we present two strategies to create artificial microscale active agents that are able to move, sense and respond to external stimuli [3-5]. In both cases, a real time feedback with the environment dictates the swimming behavior of artificial microswimmers. This new generation of adaptive active colloids constitutes an important step in the pursuit of autonomous microsystems with potential applications in microrobotics.

[1] K. Son, et.al. Nature Reviews, 13, 761-775 (2015).
[2] C. Bechinger, et.al., Revi. Mod. Phys, 88, 045006-045056 (2016).
[3] M. A Fernandez-Rodriguez et.al, Nature Communications, 11, 4223 (2020).
[4] A. R. Sprenger et.al., Langmuir, 36, 25 (2020).
[5] L. Alvarez et.al, submitted (2020).

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Materials Colloquium 2020 - December, 2nd, 16:30

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Marta Gibert (Physik-Institut, University of Zurich)

The large variety of functionalities exhibited by transition metal oxides places them as highly attractive materials both from a fundamental and applied point of view. Furthermore, the possibility to assemble oxides in epitaxial heterostructures allows us to further tune their properties and even access novel electronic behaviours not displayed by the parent compounds. Here, we will use atomically-controlled NdNiO3/SmNiO3 superlattices to show that the length scale of the interfacial coupling between metal and insulator phases is determined by balancing the energy cost of the boundary between a metal and an insulator and the bulk phase energies [1]. The structure-property relation of ferromagnetic La2NiMnO6 thin films as their thickness is reduced to just few unit cells will also be presented.

[1] Dominguez et al., Nature Materials 19, 1182 (2020)

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Materials Colloquium 2020 - November, 4th, 16:30

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Sebastian Stepanow (Magnetism and Interface Physics, D-MATL, ETHZ)

Magnetic resonance techniques are widely employed for probing the electronic and magnetic properties of solids, liquids, and molecules as well as for their elemental and structural characterization. These techniques probe with high precision the excitation of the magnetic states of an atom, or of a nucleus, and provide information on their chemical environment. For instance, electron paramagnetic resonance (EPR) is routinely used for non-invasive spin detection in materials science and chemistry research. However, conventional magnetic resonance techniques can only detect a macroscopic number of spins (~107 electron spins, ~1012 nuclear spins) and have poor spatial resolution. Scanning tunneling microscopy (STM), on the other hand, is a unique technique to achieve subatomic spatial resolution with simultaneous local spectroscopic information of single atoms and molecules on conductive surfaces.  Recently, the two techniques were combined to probe magnetic interactions and properties of single spins on surfaces. In this presentation, I will introduce the EPR-STM technique and highlight recent advances. 

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Materials Colloquium 2020 - November, 4th, 16:30

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Anna Fontcuberta i Morral (Laboratory of Semiconductor Materials, EPFL)

Solar energy harvesting constitutes of the technological paths to replace production of electrical power by burning fossil fuels. Some compound semiconductors such as GaAs and InGaAsP exhibit a high absorption coefficient in the photon energy of interest for solar energy conversion. Their commercial potential in terrestrial applications is reduced due to the scarcity (and thus high cost) of group III elements such as In and Ga. In this talk we present two approaches to render the use of this kind of materials sustainable: a strong reduction in material use through nanostructures and the replacement of group III by group II such as zinc. We find nanostructures also provide a path to increase light collection [1]. We show how II-V compounds such as Zn3P2 exhibit one magnitude higher absorption coefficient than GaAs [2]. We explain how these materials can be fabricated with high crystal quality, opening the path for the creation of alternative and sustainable compound semiconductor solar cells [3,4].

[1] P. Krogstrup et al Nature Photon 7, 306 (2013)
[2] M.Y. Swinkels et al Phys. Rev. Appl. 14, 024045 (2020)
[3] S. Escobar Steinvall et al Nanoscale Horizons 5, 274-282 (2020)
[4] R. Paul et al, Crys. Growth. Des. 20, 3816–3825 (2020)

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Materials Colloquium 2020 - October, 7th, 16:30

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Ahmad Rafsanjani (SDU Biorobotics, University of Southern Denmark)

Soft robotics surged a bioinspired evolution in robot design through their highly deformable structure by enabling robots to interact adaptively with complex environments and cooperate safely with humans. Flexible mechanical metamaterials are compliant structures with exotic mechanical properties and complex deformation behavior associated with their unique architecture rather than their chemical makeup. Integrating the complex behavior of highly deformable metamaterials into the function of soft robots allows us to embody intelligent behavior into their structure and substantially enhance their performance. In this talk, I will present several examples in which flexible metamaterials can enable us to assign primitive forms of intelligent behavior to the body of soft robots and perform simple tasks.

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Materials Colloquium 2020 - October, 7th, 16:30

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Brendan Bulfin (Professorship of Renewable Energy Carriers, D-MAVT, ETH Zürich)

Metal oxide redox cycles offer a pathway for converting heat into chemical energy via the thermal reduction of a metal oxide. The reduced metal oxide can then be used in a number of applications by re-oxidized it in a second step, utilizing the stored chemical energy and returning the oxide to its original state. Applications include; thermochemical fuel production via water or carbon dioxide splitting, thermal energy storage, and oxygen storage and separation. Here we discuss these applications, with a focus on the redox materials and their requirements. The crucial limiting factors for these applications are the thermodynamics of the reactions, which depend strongly on the choice of oxide. These limitations will be discussed along with developments in the field. Finally, a large material screening study of perovskite oxides will be presented.

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Materials Colloquium 2020 - September, 9th, 16:30

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Roland Logé (Laboratory of Thermomechanical Metallurgy, Institute of Materials, EPFL)

Laser Powder Bed Fusion (LPBF, also known as SLM, Selective Laser Melting) is a well known Additive Manufacturing technology, among the most studied in literature for metals and alloys. A number of drawbacks however still limit its range of applications, among which : (i) the high level of residual stresses; (ii) the often narrow safe processing window, which does not leave much space for microstructure optimization; (iii) the time consuming search for optimum laser parameters, which is material and machine dependent, and also relates to the part size and shape. To solve some of these issues, we introduce a new hybrid “3D LSP” manufacturing process, combining Laser Shock Peening (LSP) with LPBF. 3D LSP can efficiently strain harden a metal and convert LPBF induced Tensile Residual Stresses into CRS. It opens a range of new possibilities such as increased fatigue life or geometrical accuracy, 3D design of grain structures, and improved processability. We also present a new “translation rule”, which is able to predict optimum LPBF parameters for one material, based on those found for another material, using the concept of normalized enthalpy.

Overview Materials Colloquium 2020