Colloidal microswimmers
Active colloids are self-propelled micro- and nanoparticles that convert uniform sources of fuel into directed motion. They hold tremendous promise as model systems of living microorganism or as drug delivery vehicles. I will show some complex phenomena in artificial active matter, focusing on how liquid interfaces can be used as confining platforms to fabricate novel 2D active materials and as tools to assemble versatile active “molecules”.
Batteries for safe and large-scale energy storage
Energy storage technologies are essential to integrate and optimize the use of intermittent renewable energy sources. Not to mention that large scale energy storage can even transform the way we generate, distribute, and consume electricity. Among various options that we have at our disposal, electrochemical energy storage offers great flexibility in the design of energy storage systems. In case of large scale storage, where energy and power densities take a backseat, and cost, longevity, and safety become utmost important, aqueous batteries become favorable candidates. Through this talk I will present our recent work on the development of an aqueous rechargeable battery and discuss the underlying mechanism for its excellent performance. In addition, we will also peek into our ongoing and future efforts to enable the use of alkali metal for high energy batteries and improve the performance characteristics of aqueous batteries.
Cool stuff with ferroics – towards future solid state refrigeration
If a magnetic field is applied adiabatically to a system of magnetic
dipoles (or an electric field to a system of electric dipoles) it
heats up. If the field is removed, the temperature decreases
again. The corresponding temperature changes are particularly large in
materials close to ferroic phase transitions (e.g., ferromagnetic or
ferroelectric), and are considered as very promising route towards
more energy-efficient and less polluting cooling devices.
In this talk I will give a short introduction into the field of
“ferro-calorics” (with a focus on electro-caloric materials), and show
how we use ab-initio-based molecular dynamics simulations to better
understand what factors control the caloric response of a material and
how to optimize it for potential future technological applications.
Current challenges in the fabrication of bio-inspired composites
Biological composites achieve remarkable mechanical properties by organizing organic and inorganic building blocks into complex reinforcing architectures that find no counterparts in man-made materials. Combining the design principles underlying such intricate microstructures with the rich chemistry available in synthetic systems may offer interesting solutions for the manufacturing of sustainable and high-performance synthetic systems. In this talk, we will revisit the recent progress in the development of magnetically-assisted assembly techniques for the fabrication of bio-inspired materials and discuss the current challenges for the next major steps towards the next generation of multifunctional and high-performance composites.
Microscale metal additive manufacturing
Additive manufacturing (AM) is transforming the way we design and fabricate structures on many scales. A main driving force of this movement is the ability of AM to overcome traditional geometrical constraints imposed by subtractive manufacturing techniques. Because such geometric design restrictions become increasingly limiting at small length scales, microscale AM has the potential to expand the capabilities of microfabrication significantly.
In this talk, I will briefly review the variety of novel microscale AM techniques currently available for fabricating metal structures and touch on the resulting materials properties of structures printed with these techniques. Furthermore, I will introduce electrochemical approaches to microscale AM and summarize some of our recent work. This includes the development of a new electrochemical AM technique based on strongly spatially-confined reduction of metal ions using nanosecond pulse plating. Lastly, I will discuss possible methods for achieving voxel-by-voxel control of the printed materials’ microstructure and thus the local properties within the structure. This highlights a unique ability of electrochemical AM, which could enable the printing of complex geometries with locally tailored microstructures.
Mimicking bio-lubrication by modifying hydrogel surfaces
Biological tissues such as articular cartilage or cornea provide ultralow friction with negligible wear over many decades. A large part of such unique lubrication properties is attributed to the confinement of fluid within the branched and brushy biomolecules at the surface. Synthetic hydrogels offer the possibility to tailor their surface properties on the nanoscale and therefore can be used to mimic various biological tissues. We have modified the surface structure of hydrogels by molding them against different materials. We have also developed a 2-step nano-indentation method to accurately determine rate-dependent stiffening effects of soft matter in liquid—a property characteristic of lubricious biological tissues such as cartilage or cornea. Understanding such lubrication mechanisms is crucial for designing synthetic replacements for cartilage, contact-lens materials or even coatings for medical instruments.
Sticking with Soft Solids
Surface tension is usually neglected in solid mechanics because elasticity dominates the mechanical response of stiff materials. However, for very compliant solids, the surface tension can compete with and even dominate over the elastic response. This results in counterintuitive phenomena that sometimes directly contradict the predictions of classic elastic theory. Here, I will describe solid surface tension at work in the specific context of soft adhesive contact. In this and other examples, we find that surface tension dominates over elasticity on length scales determined by material properties, requiring us to rethink solid mechanics for soft solids. Our findings potentially impact the design of any system that relies on compliant materials with interfaces, including soft robotics, flexible and wearable electronics, functional soft medical implants, and commercial adhesives.
Electromagnetic field mapping at the nanoscale in the transmission electron microscope
Transmission electron microscopy has been revolutionized in recent years, both by the introduction of new hardware such as aberration correctors and by the development of new techniques. In this talk, I will describe how electron microscopy can be used to obtain quantitative information about not only local microstructure and chemistry in materials but also magnetic fields and electrostatic potentials with close-to-atomic spatial resolution. When combined with electron tomography and in situ techniques, this information can be obtained in three dimensions, as a function of temperature and in the presence of applied fields and reactive gases.