Seed

Coatings that prevent fouling are critical in commercial, industrial, and healthcare contexts. Wisconsin MRSEC researchers have developed new spray-based methods to make nanoporous water-repelling films and spray-on ‘slippery liquid-infused porous surfaces’ (SLIPS). These coatings are antifouling to a range of substances and microorganisms and can be produced using scalable, manufacturing-compatible methods. They also developed new antifouling ‘slippery nanoemulsion-infused porous’ (SNIPS) that use water-in-oil nanoemulsions to slowly release encapsulated cargo.

Concepts of topology recently have been brought to bear on materials designed to control sound waves. Sound wavelengths are much longer than light, making acoustic materials easier to synthesize and their behavior easier to measure. Wisconsin MRSEC researchers are using topological acoustic materials to explore topological physics and enable applications in sensing, communication, and energy transport.

Materials with a repetitive pattern the same size as the wavelength of a wave can be used to control the wave, causing it to bend, perfectly reflect or transmit, or even turn around corners. Where different patterns meet, even more exotic behavior occurs, including making highways for light or sound that only travel in one direction or where the waves cannot be dissipated. Synthesizing such materials is a major challenge, which  Wisconsin MRSEC researchers have met by adapting a family of 3D printing techniques.

The Wisconsin MRSEC has shown that molecules inside in a type of topological photonic material called a Weyl crystal can exchange energy over much larger distances. The intricate twisting structure of the material uses light to connect one molecule to others much farther away. Developing photonic Weyl crystals may contribute to more efficient LEDs and solar cells and improve molecular sensors.

The Wisconsin MRSEC has developed machine learning techniques that enable the design of new toxin sensors using liquid crystal droplets that respond to the presence of different bacterial toxins and at extremely low concentrations by changing shape and appearance. Machine learning enables computers to automatically analyze the droplet responses to measure toxin concentration and type automatically at high accuracy. More generally, these results demonstrate that the machine learning approach can quickly extract valuable information from complex datasets.

Bacteria communicate via molecular signals that they produce in high concentrations. Bacterial communication promotes the formation of biofilms that can be harmful to humans and costly to industry. We have shown that collections of individual bacterial signaling molecules interact in water to form soft materials (“self-assemble”) with spherical, layered, or cylindrical structures. Simulation images showing the formation of a spherical structure (“micelle”) are shown with corresponding experimental images.

Heusler compounds are promising materials for next generation devices for direct conversion of heat to electricity (thermoelectricity) and for magnetic computer memory. Performance in these applications depends sensitively on the arrangement of the atoms and the behavior of electrons, both of which are hard to predict and harder to control for Heuslers. We have grown thin films of FeVSb, a new Heusler compound, using molecular beam epitaxy, a kind of spray painting with “cans” of different atoms. The top picture is an electron microscope image showing the arrangement of the Fe, V, and Sb as different size dots. On the right, the image shows the material we want, FeVSb. On the left, there is a completely new, unexpected material, Fe2VSb, which is a new kind of magnet.