| Tim Sanchez1*, Daniel T. N. Chen1*, Stephen J. DeCamp1*, Michael Heymann1,2 and Zvonimir Dogic1
This study explores spontaneous motion in hierarchically assembled active matter, focusing on microtubule (MT) bundles driven by molecular motors. The researchers assemble active analogs of conventional materials such as gels, liquid crystals, and emulsions using MTs stabilized with GMPCPP. These MTs are bundled using PEG, and kinesin motors are introduced to induce active motion. The system is driven far from equilibrium by ATP hydrolysis, leading to internal flows, hydrodynamic instabilities, and self-organized structures.
Active MT bundles exhibit extensile behavior, unlike actin/myosin bundles that contract. At high concentrations, these bundles form percolating active networks (BANs) with unique properties, including internally generated fluid flows and spontaneous motility. When confined to emulsion droplets, BANs form 2D nematic liquid crystals with streaming flows controlled by internal defects. These active emulsions display autonomous motility, a property not observed in passive analogs.
The study reveals that active matter assembled from animate microscopic objects exhibits collective biomimetic properties distinct from those of inanimate materials. These properties challenge the development of a theoretical framework for engineering far-from-equilibrium material properties. The active MT networks show robust, dynamic behavior, with unique dynamics driven by cascades of MT bundles extending, buckling, fracturing, and self-healing. These dynamics are independent of kinesin velocity and are influenced by depletion agents.
The research also demonstrates that active MT liquid crystals form disclination defects, indicating nematic symmetry. These defects exhibit unique spatiotemporal dynamics, including creation, annihilation, and streaming. The study further shows that active emulsions exhibit persistent autonomous motility, a phenomenon not observed in passive systems. The findings highlight the potential of active matter for applications in soft condensed matter physics and the development of new materials with tunable properties.This study explores spontaneous motion in hierarchically assembled active matter, focusing on microtubule (MT) bundles driven by molecular motors. The researchers assemble active analogs of conventional materials such as gels, liquid crystals, and emulsions using MTs stabilized with GMPCPP. These MTs are bundled using PEG, and kinesin motors are introduced to induce active motion. The system is driven far from equilibrium by ATP hydrolysis, leading to internal flows, hydrodynamic instabilities, and self-organized structures.
Active MT bundles exhibit extensile behavior, unlike actin/myosin bundles that contract. At high concentrations, these bundles form percolating active networks (BANs) with unique properties, including internally generated fluid flows and spontaneous motility. When confined to emulsion droplets, BANs form 2D nematic liquid crystals with streaming flows controlled by internal defects. These active emulsions display autonomous motility, a property not observed in passive analogs.
The study reveals that active matter assembled from animate microscopic objects exhibits collective biomimetic properties distinct from those of inanimate materials. These properties challenge the development of a theoretical framework for engineering far-from-equilibrium material properties. The active MT networks show robust, dynamic behavior, with unique dynamics driven by cascades of MT bundles extending, buckling, fracturing, and self-healing. These dynamics are independent of kinesin velocity and are influenced by depletion agents.
The research also demonstrates that active MT liquid crystals form disclination defects, indicating nematic symmetry. These defects exhibit unique spatiotemporal dynamics, including creation, annihilation, and streaming. The study further shows that active emulsions exhibit persistent autonomous motility, a phenomenon not observed in passive systems. The findings highlight the potential of active matter for applications in soft condensed matter physics and the development of new materials with tunable properties.