Periodic Reporting for period 4 - RECONFMATTER (From colloidal joints to reconfigurable matter)
Periodo di rendicontazione: 2022-04-01 al 2023-01-31
What is the problem/issue being addressed? In biology, conformational changes are widely employed to create different functionalities in different situations. In contrast, current materials and structures made from micrometer-sized building blocks are usually rigid. They cannot adapt their shape to for example adjust to the different situation.
In this project, we are investigating how we can create materials and structures with flexible connections between the building blocks and how we harness this feature to create reconfigurable materials.
Why is it important for society? Micrometer sized particles are powerful model systems that allow scientists to study otherwise complex phenomena. In this project, we investigate the implications of flexibility on the behavior of structures to gain new insights into how for example polymers and biological molecules adapt their shape to different needs. Ultimately, we dream of using our insights to create materials with adaptable mechanical and optical properties which could be employed in sensors, actuators, advanced coatings and more complex functional devices such as microrobots.
What are the overall objectives? We will elucidate how bond flexibility can be exploited to create and understand flexible structures. We will build small units with internal degrees of freedom and study how they interact and organize. Finally, we will introduce active and actuatable elements to induce a controlled switching between different configurations and create shape-changing and self-propelled structures.
Conclusions: We developed, characterized and optimized colloidal particles with DNA-based bonds that allow rearrangements. We used both self-assembly as well as manual assembly by optical tweezers to create flexible chains, rings, colloidal molecules, and lattices of these colloidal particles. We studied how rearrangements after bonding and other parameters such as size, particle shape and number ratio affect the assembly pathways towards ordered, well-controlled structures. We quantified their diffusive behavior and conformational changes and used our findings to validate theoretical predictions. We investigated microswimmers and discovered that they adapt their velocity to the properties of the nearby wall, keep a very stable distance to the wall, and synchronize their motion due to a competition between repulsive and attractive interactions. With these insights we were able to develop proof-of-principle materials with global reconfiguration modes.
In this project, we are investigating how we can create materials and structures with flexible connections between the building blocks and how we harness this feature to create reconfigurable materials.
Why is it important for society? Micrometer sized particles are powerful model systems that allow scientists to study otherwise complex phenomena. In this project, we investigate the implications of flexibility on the behavior of structures to gain new insights into how for example polymers and biological molecules adapt their shape to different needs. Ultimately, we dream of using our insights to create materials with adaptable mechanical and optical properties which could be employed in sensors, actuators, advanced coatings and more complex functional devices such as microrobots.
What are the overall objectives? We will elucidate how bond flexibility can be exploited to create and understand flexible structures. We will build small units with internal degrees of freedom and study how they interact and organize. Finally, we will introduce active and actuatable elements to induce a controlled switching between different configurations and create shape-changing and self-propelled structures.
Conclusions: We developed, characterized and optimized colloidal particles with DNA-based bonds that allow rearrangements. We used both self-assembly as well as manual assembly by optical tweezers to create flexible chains, rings, colloidal molecules, and lattices of these colloidal particles. We studied how rearrangements after bonding and other parameters such as size, particle shape and number ratio affect the assembly pathways towards ordered, well-controlled structures. We quantified their diffusive behavior and conformational changes and used our findings to validate theoretical predictions. We investigated microswimmers and discovered that they adapt their velocity to the properties of the nearby wall, keep a very stable distance to the wall, and synchronize their motion due to a competition between repulsive and attractive interactions. With these insights we were able to develop proof-of-principle materials with global reconfiguration modes.
We developed, characterized and optimized colloidal particles with DNA-based bonds that allow rearrangements yet are stable against unspecific aggregation and spontaneous rigidification. We used both self-assembly as well as manual assembly by optical tweezers to create flexible chains, rings, colloidal molecules, and lattices of these colloidal particles.
We studied how rearrangements after bonding and other parameters such as size, particle shape and number ratio affect the assembly pathway towards ordered, well-controlled structures, which allowed us to significantly increase the yield and fidelity of the resulting structures. Particle shape and number ratio can be exploited to control the number of bonds per particle as well as their angular range of motion. We exploited the latter to confine particles to specific regions and showed that this confinement can be lifted in situ by an elevation of temperature. We demonstrated these concepts by assembling finite sized clusters, so called “flexible colloidal molecules” and showed that the bond flexibility allowed us to assemble finite-sized clusters of uniform shape in high yield, which has been challenging before. We successfully assembled these “flexible colloidal molecules” in various shapes and quantified their assembly dynamics. We found that bond flexibility is crucial for achieving maximum valence and the degree of flexibility impacts the assembly speed. Using an anisotropic particle shape, control over bond directionality and angular motion range was implemented. We exploited our insights gained from assembling colloidal molecules for assembling larger structures to creating square lattices with floppy reconfiguration modes. We quantified these modes and explored approaches to controllable switch between different conformations.
Finally, we investigated self-propelled elements (so-called active particles) for integration with reconfigurable structures. We employed spheres half-coated with a catalytically active material and found that their velocity is strongly dependent on the material that they are moving on, in particular, it depends on the slip length of the substrate. Since the influence of slip on particle motion hinges on the distance with which particles move from a substrate, we devised a new strategy to extract this crucial information from the diffusive contribution to their motion. We found the striking result that catalytically propelled particles assume a preferred height over the substrate that persist for a wide range of parameters and is in stark contrast to the behavior of passive particles. We discovered that microswimmers synchronize their motion due to a competition between repulsive and attractive interactions. We quantified their velocity distribution, and found remarkable intermittency of the active motion with robust power-law velocity distributions which we could model by an interplay of active force, limited by the velocity dependent fluid gradient, and hydrodynamic drag.
Our results were published in high-quality journals, and presented at over 30 conferences, workshops and seminars. We have engaged with the general public through lectures, school visits, press releases, and twitter.
We studied how rearrangements after bonding and other parameters such as size, particle shape and number ratio affect the assembly pathway towards ordered, well-controlled structures, which allowed us to significantly increase the yield and fidelity of the resulting structures. Particle shape and number ratio can be exploited to control the number of bonds per particle as well as their angular range of motion. We exploited the latter to confine particles to specific regions and showed that this confinement can be lifted in situ by an elevation of temperature. We demonstrated these concepts by assembling finite sized clusters, so called “flexible colloidal molecules” and showed that the bond flexibility allowed us to assemble finite-sized clusters of uniform shape in high yield, which has been challenging before. We successfully assembled these “flexible colloidal molecules” in various shapes and quantified their assembly dynamics. We found that bond flexibility is crucial for achieving maximum valence and the degree of flexibility impacts the assembly speed. Using an anisotropic particle shape, control over bond directionality and angular motion range was implemented. We exploited our insights gained from assembling colloidal molecules for assembling larger structures to creating square lattices with floppy reconfiguration modes. We quantified these modes and explored approaches to controllable switch between different conformations.
Finally, we investigated self-propelled elements (so-called active particles) for integration with reconfigurable structures. We employed spheres half-coated with a catalytically active material and found that their velocity is strongly dependent on the material that they are moving on, in particular, it depends on the slip length of the substrate. Since the influence of slip on particle motion hinges on the distance with which particles move from a substrate, we devised a new strategy to extract this crucial information from the diffusive contribution to their motion. We found the striking result that catalytically propelled particles assume a preferred height over the substrate that persist for a wide range of parameters and is in stark contrast to the behavior of passive particles. We discovered that microswimmers synchronize their motion due to a competition between repulsive and attractive interactions. We quantified their velocity distribution, and found remarkable intermittency of the active motion with robust power-law velocity distributions which we could model by an interplay of active force, limited by the velocity dependent fluid gradient, and hydrodynamic drag.
Our results were published in high-quality journals, and presented at over 30 conferences, workshops and seminars. We have engaged with the general public through lectures, school visits, press releases, and twitter.
We have established a framework for creating and understand flexible structures and reconfigurable materials. This has enabled us to study the impact of rearranging bonds on the assembly, diffusive behavior and mechanical properties of flexible colloidal structures. Our insights have led to the first proof-of-principle material with global reconfiguration modes, the first step towards create materials with adaptable mechanical and optical properties which could be employed in sensors, actuators, advanced coatings and more complex functional devices such as microrobots. Our discoveries made with synthetic self-propelled particles, which are model systems for microorganisms, have implications for the design of antimicrobial surfaces, treatment of infections and understanding the swimming behavior of microorganisms in general.