Fig. 1. Basic concept of hybrid bionic moisture responsive shape-morphing slippery surface inspired from multi-form carnivorous plants. The Nepenthes pitcher plant catches insects passively with the help of a lubricant-infused slippery surface. The Dionaea muscipula preys actively through a stimuli-responsive actuation mechanism. We combined the slippery surfaces (passive prey) and stimuli-responsive actuation (active prey), so we proposed a hybrid bionic moisture deformable slippery surface-based GO, which enables both active and passive droplet manipulation. GO: graphene oxide; RGO, reduced GO.

Fig. 2. Fabrication, morphology, and element characterization of the moisture responsive shape-morphing slippery surface. (a) Fabrication processing of the moisture responsive shape-morphing slippery surface. A femtosecond (fs) laser was used to reduce GO and induce microstructures similar to the Nepenthes pitcher plant. A waterproof lubricant was infused into the LRGO surface to form the slippery surface. (b) The scanning electron microscope (SEM) image of the Nepenthes pitcher plant. (c) The SEM image of the LRGO surface. (d, e) The confocal laser scanning microscope (CLSM) images of the LRGO. (f) The Raman spectra, (g) Fourier transform infrared (FTIR) spectra, (h) X-ray photoelectron spectroscopy (XPS) survey spectra, and (i) C1s XPS spectra of the GO and LRGO sides of the bilayer actuator.

Fig. 3. The properties of the lubricant-infused slippery surface. (a) Schematic illustration of the water droplet sliding behavior. (b) The lubricant-infused slippery surface's water contact angle (CA) and sliding angle (SA). The scale bar is 1 mm. (c) The photographs of a droplet (R6G labeled) sliding behavior on a tilted surface. (d) The overturning behavior of a ladybird on a general paper surface. The scale bar is 5 mm. (e) The overturning and sliding behavior of a ladybird on our lubricant-infused slippery surface. The scale bar is 5 mm. (f) The durability of CA and SA on oil-infused LRGO surface for 1000 cycles. (g) Sliding displacement of a water droplet vs. time. The tilted angles θ = 5°, 10°, and 15°, respectively. (h) The sliding behavior of various liquid droplets on our lubricant-infused slippery surface. The tilted angle θ = 30°.

Fig. 4. Moisture-response deformations of the oil-LRGO/GO actuator. (a) Schematic illustration of the moisture responsive shape-morphing mechanism. Under the moisture actuation, water molecules are selectively adsorbed by the GO layer, which leads to the swelling of the GO side. The strain mismatch induces bending deformation. (b) Curvature-RH curves of the oil-LRGO/GO, LRGO/GO, and GO films on RH. (c) Responsive/recovery properties of the oil-LRGO/GO and LRGO/GO actuator. (d) The stability of the oil-LRGO/GO and LRGO/GO actuator for cycling use (1000 times). (e) The moisture-response Dionaea muscipula actuator with a slippery inner surface. The left scheme is the working model. The right images are the photographs of the deformation and droplet sliding behavior of the Dionaea muscipula actuator. The scale bar is 2 cm.

Fig. 5. The manipulation of droplets on moisture responsive shape-morphing slippery surface. (a) Schematic illustration for the active and passive manipulation of a droplet containing live tubificidaes using the shape-morphing slippery surface. (b) The photographs of shape-morphing slippery frog tongue. The scale bar is 1.5 cm. (c) A smart water droplet harvesting flower. Every flower petal is made of the shape-morphing slippery surface (oil-LRGO/GO). The scale bar is 1.5 cm. (d) Moisture triggered active approach to water droplets containing live tubificidaes and the passive sliding behavior on the shape-morphing slippery surface. The scale bar is 0.5 cm. (e) The corresponding trajectory of the water droplet peripheries during the dynamic process. (f) The curvature changes of the shape-morphing slippery surface in (d). (g) The open-circuit voltage and (h) short-circuit current.