Self-powered artificial nanomotors are currently attract-9 ing increased interest as mimics of biological motors but also as 10 potential components of nanomachinery, robotics, and sensing devices.
11We have recently described the controlled shape transformation of 12 polymersomes into bowl-shaped stomatocytes and the assembly of
Every
living cell is a compartmentalized out-of-equilibrium system
exquisitely able to convert chemical energy into function. In order
to maintain homeostasis, the flux of metabolites is tightly controlled
by regulatory enzymatic networks. A crucial prerequisite for the development
of lifelike materials is the construction of synthetic systems with
compartmentalized reaction networks that maintain out-of-equilibrium
function. Here, we aim for autonomous movement as an example of the
conversion of feedstock molecules into function. The flux of the conversion
is regulated by a rationally designed enzymatic reaction network with
multiple feedforward loops. By compartmentalizing the network into
bowl-shaped nanocapsules the output of the network is harvested as
kinetic energy. The entire system shows sustained and tunable microscopic
motion resulting from the conversion of multiple external substrates.
The successful compartmentalization of an out-of-equilibrium reaction
network is a major first step in harnessing the design principles
of life for construction of adaptive and internally regulated lifelike
systems.
Micro- and nanomotors and their use for biomedical applications have recently received increased attention. However, most designs use top-down methods to construct inorganic motors, which are labour-intensive and not suitable for biomedical use. Herein, we report a high-throughput design of an asymmetric hydrogel microparticle with autonomous movement by using a microfluidic chip to generate asymmetric, aqueous, two-phase-separating droplets consisting of poly(ethylene glycol) diacrylate (PEGDA) and dextran, with the biocatalyst placed in the PEGDA phase. The motor is propelled by enzyme-mediated decomposition of fuel. The speed of the motors is influenced by the roughness of the PEGDA surface after diffusion of dextran and was tuned by using higher molecular weight dextran. This roughness allows for easier pinning of oxygen bubbles and thus higher speeds of the motors. Pinning of bubbles occurs repeatedly at the same location, thereby resulting in constant circular or linear motion.
Natural
materials provide an increasingly important role model for the development
and processing of next-generation polymers. The velvet worm Euperipatoides rowelli hunts using a projectile, mechanoresponsive
adhesive slime that rapidly and reversibly transitions into stiff
glassy polymer fibers following shearing and drying. However,
the molecular mechanism underlying this mechanoresponsive behavior
is still unclear. Previous work showed the slime to be an emulsion
of nanoscale charge-stabilized condensed droplets comprised primarily
of large phosphorylated proteins, which under mechanical shear coalesce
and self-organize into nano- and microfibrils that can be drawn into
macroscopic fibers. Here, we utilize wide-angle X-ray diffraction
and vibrational spectroscopy coupled with in situ shear deformation to explore the contribution of protein conformation
and mechanical forces to the fiber formation process. Although previously
believed to be unstructured, our findings indicate that the main phosphorylated
protein component possesses a significant β-crystalline structure
in the storage phase and that shear-induced partial unfolding of the
protein is a key first step in the rapid self-organization of nanodroplets
into fibers. The insights gained here have relevance for sustainable
production of advanced polymeric materials.
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