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

Abstract

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.

Photoactivated Artificial Molecular Motors

“…The net result of this combination is a photostationary state in which the macroscopic size of the hydrogel sample can be reversibly controlled through light irradiation (Figure a–c). More recently, the authors expanded their understanding on the influence of the nature of the polymer network on hydrogel actuation . The photon density available per motor unit and the amount of free volume in the polymer network were found to be key parameters to improve the efficiency and applicability.…”

“…Photodriven chain entanglement was also exploited by Giuseppone and co-workers to control the macroscopic properties of a polymeric system. , Polyethylene glycol-functionalized second-generation stilbene motors were used to provide cross-linked networks resulting in hydrogel formation. ,, Upon light irradiation, the degree of entanglement of the polymers increases due to the unidirectional rotation, similar to the “whirligig” system. This results in the motors within the hydrogel being pulled toward each other with a consequent net stiffening of the structure (Figure a,b).…”

“…More recently, the authors expanded their understanding on the influence of the nature of the polymer network on hydrogel actuation. 82 The photon density available per motor unit and the amount of free volume in the polymer network were found to be key parameters to improve the efficiency and applicability. Their careful optimization led to the preparation of self-standing gels working as bending actuators that display a 400-fold enhancement in the mechanical work that can be extracted from the system.…”

Out‐of‐Equilibrium Mechanical Disruption of β‐Amyloid‐Like Fibers using Light‐Driven Molecular Motors

“…[ 20 ] Conversely, examples of real molecular motors that can truly influence materials’ properties because of their autonomous and continuous unidirectional motion (independently of their state) remain scarce. [ 21,22 ] However, this kind of approach is of particular fundamental and technological interests because it holds the potential to generate continuous mechanical work within a system, and therefore to access advanced responsive out‐of‐equilibrium materials displaying thermodynamic properties approaching those encountered in living systems. [ 23 ]…”

Transducing chemical energy through catalysis by an artificial molecular motor

“…Artificial molecular motors [17][18][19][20][21][22][23][24] and pumps [25][26][27][28][29][30][31][32][33][34] can provide insights regarding the mechanisms of powered molecular-level motion. [13][14][15][16] Molecular machines have been interfaced with other components to perform tasks, 29,32,[35][36][37][38] including the use of light-driven rotary motors to disrupt cell membranes 35 and drive the contraction of gels. [36][37][38] However, performing work with artificial catalysis-driven molecular motors, the synthetic analogues of motor proteins, has remained elusive.…”