Bending Actuation of Hydrogels through Rotation of Light-Driven Molecular Motors

The unidirectional rotation of chemically crosslinked light-driven molecular motors is shown to progressively shift the swelling equilibrium of hydrogels. The concentration of molecular motors and the initial strand density of the polymer network are key parameters to modulate the macroscopic contraction of the material, and both parameters can be tuned using polymer chains of different molecular weights. These findings led to the design of optimized hydrogels revealing a half-time contraction of approximately 5 min. Furthermore, under inhomogeneous stimulation, the local contraction event was exploited to design useful bending actuators with an energy output 400 times higher than for previously reported self-assembled systems involving rotary motors. In the present configuration, we measure that a single molecular motor can lift up loads of 200 times its own molecular weight.

Automated summary

The unidirectional rotation of chemically crosslinked light-driven molecular motors changes the swelling equilibrium of hydrogels progressively. The concentration of molecular motors and the initial strand density of the polymer network are crucial parameters for controlling the macroscopic contraction of the material, which can be adjusted by using polymer chains with different molecular weights. These findings led to the development of optimized hydrogels with a half-time contraction of approximately 5 min. Moreover, by harnessing the local contraction event under inhomogeneous stimulation, bending actuators with significantly higher energy output compared to previous self-assembled systems involving rotary motors were designed, allowing a single molecular motor to lift loads 200 times its own molecular weight.