AC) stimuli. Xiao et al. [30] fabricated a graphene/poly(vinyldene fluoride) (PVDF) bilayer actuator by coating of PVDF solution onto a porous graphene paper. The hybrid film exhibited electrodriven vibration having rapid response rate, large displacement, and durable stability. In those electrothermal actuators, Joule heating was generated when electric current passed through the graphene film. Then the thermal expansion resulted in the large amount of deflection of the graphene/ polymer bilayer film. Polymer actuator is advantageous because of its high sensitivity, low energy input, and larger expansion rate. In this work, reduced graphene oxide (RGO)-based actuator was fabricated by spin-coating a reduced graphene oxide solution onto a polymer substrate obtaining a bilayer structure actuator. Poly dimethylsiloxane (PDMS) or polyethylene (PE) polymer substrate was used to support the electric-heated RGO layer and enlarge the thermal expansion deformation. [31] The bilayer film showed responsive bending motion under DC or AC voltage driving. Several actuate modes were proposed according to the bilayer structure design and driving current control. Experimental Section Preparation of RGOGraphite powder (2 g) was added into 46 mL of concentrated H 2 SO 4 , followed by adding 1 g NaNO 3 into above mixture under stirring and cooling in an ice bath condition. The mixture was continuous stirred while 6 g KMnO 4 was added slowly to keep the temperature of mixture below 5 °C. Then the mixture was kept at 35 °C for 30 min, followed by adding 90 mL deionized water while stirring, and the temperature would rise up to 95 °C. The mixture was kept stirring for a further 30 min, and 100 mL deionized water and 10 mL 30% H 2 O 2 were added in sequence. The oxidized material was then washed with 1:10 (v:v) HCl solution one time and deionized water three times to remove metal ions, followed by centrifugation. The collected product was dried in a vacuum drying oven at 45 °C.To obtain RGO, the as-synthesized GO powder (10 mg) was suspended in 20 mL of distilled water by ultrasonication until a yellowish-brown colloid was obtained. Subsequently, few drops of ammonia solution (35%) were added to increase the pH up to 8 allowing stability of the sheets. 15 µL hydrazine hydrate (0.1 m) solution was added to the above solution and refluxed at 98 °C for 100 min in a water bath, affording the formation Electrothermal Actuator Electrodriven bilayer actuator is designed and fabricated by spin-coating a reduced graphene oxide solution onto a polymer substrate. The bonded interface properties, electrical and thermal conductivities are characterized through scanning electron microscopy and X-ray diffraction. The bilayer actuator exhibits fast and large bending response when a direct current voltage is applied to the graphene layer. Whereas it exhibits oscillation when an alternating current voltage is applied to the bilayer actuator. The effects of the layer structure and the electro-operation methods on the bending motions are studied. Two new ...

A multi‐wavelength light drivable bilayer actuator is fabricated by depositing a thin layer of reduced graphene oxide (RGO) onto a flexible poly(dimethyl siloxane) (PDMS) substrate. The RGO/PDMS bilayer film shows fast and reversible bending/unbending motions upon exposure to UV light, visible light, or near‐infrared light (NIR). The photo‐thermal effect of the pump lights is studied by measuring and comparing the light induced temperature rises on RGO/PDMS film. The results demonstrate that the RGO absorbs and converts the light into heat. Thus the bilayer film undergoes thermal expansion under light irradiation. The calculated thermal expansion of the RGO thin layer is smaller than that of the PDMS layer, which results in the bilayer actuator bending towards the layer on the RGO side. Oscillational motion on the bilayer film is successfully achieved using continuous light irradiation on an offset sandwiched RGO/PDMS bilayer cantilever. Light induced motion on the RGO based film provides a new strategy for absorbing light energy and outputting photomechanical work.

We demonstrate straight and bent silicon waveguide junctions using the junction offsets. More than 20% reduction (about 0.02 dB) of the junction connection losses are obtained for the junction using 25 nm offset with bent radii 1.5 lm, compared with the junction without the offset. We also show that the performance of the silicon waveguide racetrack resonators can be improved by introducing a lateral offset at the straight-to-bent waveguide junctions. About 0.5 dB increase in drop power is observed for the racetrack resonators with junction offset.

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