Controllable and Stable Deformation of a Self-Healing Photo-Responsive Supramolecular Assembly for an Optically Actuated Manipulator Arm

Abstract

It is highly challenging to achieve an optically deformable polymer with good controllability, stability, and self-healability for fabricating an optically controlled microrobotics. Here, we present a photo-responsive self-healing supramolecular assembly cross-linked by 3,3',5,5'-azobenzenetetracarboxylic acid (t-Azo) enabling the controllable and stable deformation. The network (PAA-u) of polyacrylic acid (PAA) grafted with 2-ureido-4[1 H]-pyrimidinone (UPy) is formed via multiple intermolecular hydrogen bonds (H-bonds) between UPy and t-Azo moieties. Molecular H-bonds stabilize the cis-isomer, enables stress transfer at the interface, and also contributes to fast healability. The PAA-u/t-Azo assembly shows a green-light-induced bending deformation, which recovers its shape under the irradiation of UV light. On the basis of this controllable and reversible deformation, the PAA-u/t-Azo "hand" realizes reversible light-driven grabbing and releasing of an object by optimizing bending and recovery. The assembly also shows a fast and excellent self-healing performance irradiated by green light during deformation. The multiple-H-bonding-cross-linked assembly with stable deformation and fast self-healability can be used for the development of a multitude of advanced microrobotics.