For miniaturized shape-reconfigurable soft electronics, smart materials with material intelligence are necessary to achieve on-demand remotely controlled actuation under external stimuli. Toward this end, azobenzene functionalized liquid crystalline polymer networks (azo-LCN) can be a promising candidate for shape-tunable soft electronics owing to their external stimuli responsivity and the programmability. However, azo-LCNs are electrically insulating polymers and there are trade-off relationship between mechanical strength and actuation performance. In this presentation, we report enhancement of both mechanical and electrical properties of azo-LCNS without sacrifice of actuation capability of the azo-LCN by the introduction of reduced graphene oxide (rGO). The mismatch of coefficient of thermal expansion (CTE) between azo-LCN and rGO results in enhanced storage modulus of the azo-LCN/rGO increases by a factor of 5 (E=6.4 GPa) yet with larger photo/thermal responsivity in comparison with the neat azo-LCN. Also, the electrical conductivity of the azo-LCN is recorded to be 380 S cm<sup>-1</sup>. Upon exposure to broadband UV, the in-plane bending angle of azo-LCN/rGO is drastically enhanced for both forward and backward bending with respect to the light source than that of the neat azo-LCN. The out-plane 3D shape transition is achieved by simply adjusting the cutting angle and patterning designs of azo-LCN/rGO. The azo-LCN/rGO also have demonstrated multi-stimuli responsivity including actuating under near infrared (NIR), focused sunlight and direct heating. Finally, we demonstrate simultaneous shape-reconfiguration of kirigami-engineered azo-LCN/rGO by passive-type mechanical stretching and active-type photomechanical actuation without deterioration of electrical performance for stretchable electronics.

Stretchable electronics with light-triggered shape-reconfiguration: Reduced graphene oxide patterned azo-liquid crystalline polymer networks with enhanced mechanical and actuating performance

ACS Fall 2021

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