Enable Multi-Stimuli-Responsive Biomimetic Actuation with Asymmetric Design of Graphene-Conjugated Conductive Polymer Gradient Film

In this paper, multiresponsive actuators based on asymmetricdesignof graphene-conjugated poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate)(PEDOT:PSS) gradient films have been developed by a simple drop castingmethod. The biomimetic actuation is attributed to the hygroscopicexpansion property of PEDOT:PSS and the gradient distribution of graphenesheets within the film, which resembles the hierarchical swellingtissues of some plants in nature. Graphene-conjugated PEDOT:PSS (GCP)actuators exhibit reversible bending behavior under multistimuli suchas moisture, organic vapor, electrothermal, and photothermal heating.Noticeably, the bending curvature reaches 2.15 cm(-1) under applied voltage as low as 1.5 V owing to the high electricalconductivity of GCP actuator. To mimic the motions of nyctinasticplants, a GCP artificial flower that spreads its petals under sunlightillumination has been fabricated. GCP actuators have been also demonstratedas intelligent light-controlled switches for light-emitting diodesand smart curtains for thermal management. Not only do the GCP gradientfilms exhibit potential applications in flexible electronics and energyharvesting/storage devices but also the facile fabrication of multiresponsiveGCP actuators may shed light on the development of soft robotics,artificial muscles, wearable electronics, and smart sensors.