Periodic Reporting for period 2 - SpAM (Spinning Active Matter)
Berichtszeitraum: 2023-04-01 bis 2024-09-30
Problem being addressed
Active-matter physics describes the mesmerizing dynamics of interacting motile bodies: from bird flocks and cell colonies, to collections of synthetic units independently driven far from equilibrium. Until now, however, all man-made realizations have been merely limited to 2D model systems. We will introduce a paradigm shift to upgrade the status of synthetic active matter from aesthetic 2D experiments to genuine 3D materials and metamaterials with unanticipated engineering applications.
Why is it important for society?
Active matter physics had been one of the more active field in soft-condensed matter physics for more than 20 years. However the potential of active matter has been strongly hindered by the limitation of experimental research to model two-dimensional systems assembled from self-propelled units. In order to transform the field of active matter from a fundamental field to a line of research with potential engineering applications we need first to let active matter explore the third dimension and second to motorise a broader class of materials and metamaterials where activity does not only rhyme with self-propulsion but also with spontaneous rotation.
Overall objective:
The essential goal is to construct the first generation of three-dimensional active materials and metamaterials and to lay out the foundations of spinning active matter. I articulate my project around three complementary aims, all based on a unique experimental platforms combining high-content microfluidics, advanced 3D printing techniques, and statistical analysis of high content experiments.
Active-matter physics describes the mesmerizing dynamics of interacting motile bodies: from bird flocks and cell colonies, to collections of synthetic units independently driven far from equilibrium. Until now, however, all man-made realizations have been merely limited to 2D model systems. We will introduce a paradigm shift to upgrade the status of synthetic active matter from aesthetic 2D experiments to genuine 3D materials and metamaterials with unanticipated engineering applications.
Why is it important for society?
Active matter physics had been one of the more active field in soft-condensed matter physics for more than 20 years. However the potential of active matter has been strongly hindered by the limitation of experimental research to model two-dimensional systems assembled from self-propelled units. In order to transform the field of active matter from a fundamental field to a line of research with potential engineering applications we need first to let active matter explore the third dimension and second to motorise a broader class of materials and metamaterials where activity does not only rhyme with self-propulsion but also with spontaneous rotation.
Overall objective:
The essential goal is to construct the first generation of three-dimensional active materials and metamaterials and to lay out the foundations of spinning active matter. I articulate my project around three complementary aims, all based on a unique experimental platforms combining high-content microfluidics, advanced 3D printing techniques, and statistical analysis of high content experiments.
Design, fabrication, and motorization of spinning colloidal particles of custom shapes.
To achieve the fabrication of micron-sized particles of controlled and custom shapes, we have combined techniques from colloidal synthesis and 3D nano-printing. This combination has allowed us to produce micron-sized micromachines whose rotational degrees of freedom are motorized by an electrohydrodynamic instability commonly referred to as Quincke electro-rotation.
We have produced large collections of spinning bodies and studied their collective dynamics.
Active Hydraulics
When active spinning bodies are in contact with a solid surface, their spontaneous rotation can be readily converted into rolling motion. When colloidal rollers interact, they self-assemble into spontaneously flowing fluids, fluids that can flow even in the absence of pressure gradients and boundary motion (pumps). We have used this model system to lay out the basic laws of active-fluid hydraulics. To do so, we studied experimentally how colloidal roller fluid self-organizes their flows in channel networks. We showed that their emergent flow patterns are generically frustrated and degenerate as soon as the hydraulic networks include junctions with an odd coordination number. Combining experiments, theory, and numerical simulations, we explained quantitatively the geometry of active hydraulic flows using concepts and tools from frustrated magnetism.
Conditional activity
We have shown that rod-shaped spinners realize an unanticipated form of active matter. Unlike all other instances of synthetic active matter, the activity of anisotropic Quincke spinners is not a priori imposed; it is conditioned by the structure of their environment. Conditional activity is not peculiar to our rod-shaped spinners but is the hallmark of all active matter formed by living organisms. Think of a pedestrian walking in a crowded environment; its walking speed strongly depends on the local packing fraction. Combining experiments, simulations, and theory, we have shown that active liquids powered by conditional activity generically phase separate according to an unanticipated scenario.
Active cristalline solids
Conceptually, the simplest form of active matter would be a crystal assembled of active units. However, unlike liquid active matter, active crystals have strongly resisted experimental investigations. Assembling colloidal crystals from spinning colloidal particles, we have quantitatively investigated the stability of this new form of ordered active matter and explained why their melting cannot be explained from equilibrium principles.
Active metamaterials
The vast majority of active matter physics has hitherto focused on self-assembly. We initiated a paradigm shift and devised the first generation of microscopic active metamaterials assembled from active spinning machines. We are currently investigating how unprogrammed functionalities can emerge from the interactions between active micromachines.
To achieve the fabrication of micron-sized particles of controlled and custom shapes, we have combined techniques from colloidal synthesis and 3D nano-printing. This combination has allowed us to produce micron-sized micromachines whose rotational degrees of freedom are motorized by an electrohydrodynamic instability commonly referred to as Quincke electro-rotation.
We have produced large collections of spinning bodies and studied their collective dynamics.
Active Hydraulics
When active spinning bodies are in contact with a solid surface, their spontaneous rotation can be readily converted into rolling motion. When colloidal rollers interact, they self-assemble into spontaneously flowing fluids, fluids that can flow even in the absence of pressure gradients and boundary motion (pumps). We have used this model system to lay out the basic laws of active-fluid hydraulics. To do so, we studied experimentally how colloidal roller fluid self-organizes their flows in channel networks. We showed that their emergent flow patterns are generically frustrated and degenerate as soon as the hydraulic networks include junctions with an odd coordination number. Combining experiments, theory, and numerical simulations, we explained quantitatively the geometry of active hydraulic flows using concepts and tools from frustrated magnetism.
Conditional activity
We have shown that rod-shaped spinners realize an unanticipated form of active matter. Unlike all other instances of synthetic active matter, the activity of anisotropic Quincke spinners is not a priori imposed; it is conditioned by the structure of their environment. Conditional activity is not peculiar to our rod-shaped spinners but is the hallmark of all active matter formed by living organisms. Think of a pedestrian walking in a crowded environment; its walking speed strongly depends on the local packing fraction. Combining experiments, simulations, and theory, we have shown that active liquids powered by conditional activity generically phase separate according to an unanticipated scenario.
Active cristalline solids
Conceptually, the simplest form of active matter would be a crystal assembled of active units. However, unlike liquid active matter, active crystals have strongly resisted experimental investigations. Assembling colloidal crystals from spinning colloidal particles, we have quantitatively investigated the stability of this new form of ordered active matter and explained why their melting cannot be explained from equilibrium principles.
Active metamaterials
The vast majority of active matter physics has hitherto focused on self-assembly. We initiated a paradigm shift and devised the first generation of microscopic active metamaterials assembled from active spinning machines. We are currently investigating how unprogrammed functionalities can emerge from the interactions between active micromachines.
Progress beyond the state of the art:
— Fabrication of a new generation of active particles and active micromachines.
— Definition of the fundamental laws of active-fluid hydraulics
— Identification of the generic consequences of conditional activity on the phase behaviour of active liquids
— Fabrication of the first active colloidal crystals, characterisation and explanation of their unique melting dynamics.
— Realization of the first microscopic active metamaterials from coupled micro machines
Expected results until the end of the project:
— Realization of the first three dimensional active crystals, investigation of their response, fluctuations and topological defect dynamics
— Realization of the first three dimensional active metamaterials with emergent functionalities
— Fabrication of a new generation of active particles and active micromachines.
— Definition of the fundamental laws of active-fluid hydraulics
— Identification of the generic consequences of conditional activity on the phase behaviour of active liquids
— Fabrication of the first active colloidal crystals, characterisation and explanation of their unique melting dynamics.
— Realization of the first microscopic active metamaterials from coupled micro machines
Expected results until the end of the project:
— Realization of the first three dimensional active crystals, investigation of their response, fluctuations and topological defect dynamics
— Realization of the first three dimensional active metamaterials with emergent functionalities