advances.sciencemag.org/cgi/content/full/1/10/e1500533/DC1

Supplementary Materials for

Origami-inspired active graphene-based paper for programmable

instant self-folding walking devices

Jiuke Mu, Chengyi Hou, Hongzhi Wang, Yaogang Li, Qinghong Zhang, Meifang Zhu

Published 6 November 2015, Sci. Adv. 1, e1500533 (2015)

DOI: 10.1126/sciadv.1500533

This PDF file includes:

Fig. S1. Schematic illustration of the MGM having a dual-gradient structure with

vertical and lateral gradients.

Fig. S2. The XPS survey spectra of GO-PDA/HI and rGO.

Fig. S3. Powder XRD patterns of GO, GO-PDA, GO-PDA/HI, rGO, and graphite.

Fig. S4. Raman spectra of GO, GO-PDA, GO-PDA/HI, and rGO.

Fig. S5. Optical images show the adhesive tape–peeling method (top).

Fig. S6. The gravimetric tensile strength of GO-PDA/rGO and rGO regions.

Fig. S7. The thickness profiles of the GO-PDA line with light on and off.

Fig. S8. The digital photograph of the moisture control device and the recovery

performance tested at different relative humidity environments.

Fig. S9. Schematic illustration of θ, γ, L, F, and ρ (L is the width of the GO-PDA

line; F is the stress generated by the GO-PDA line; ρ is the radius of curvature; θ

is the bending angle of MGM; γ is the supplementary angles of θ).

Fig. S10. Schematic illustration of the preparation of a self-folding box.

Fig. S11. The stress generated by the MGMs (middle and right) were measured

on the universal testing machine (Instron Model 5969) with on/off NIR light

irradiations (left).

Fig. S12. Cross-sectional field emission SEM images indicating GO-PDA/rGO

regions for different GO-PDA lines: (A) 1 mm, (B) 3 mm, and (C) 5 mm.

Fig. S13. Temperature-change curves and the energy conversion efficiency of

MGM.

Fig. S14. Cycle output test of MGM under on/off irradiations.

Fig. S15. Optical image of the walking behavior of the walking device driven by

NIR light.

Fig. S16. The turning behavior of the walking device.

Fig. S17. Turning angle of the walking devices as a function of time as light is

turned on and off for different illumination areas.

Fig. S18. Optical images show the walking device progressing over a virtual map

driven by light irradiation (scale bar, 3 cm).

Fig. S19. The schematic illustration and optical image showing the measurement

of the bending angle using a laser displacement sensor.

Table S1. Maximum output stress, bending angle, and theoretical bending angle

as a function of GO-PDA width (average value of data).

Note S1. Calculations of the maximum energy conversion efficiency of our

actuator.

Methods

Legends for movies S1 to S6

Other Supplementary Material for this manuscript includes the following:

(available at advances.sciencemag.org/cgi/content/full/1/10/e1500533/DC1)

Movie S1 (.mp4 format). The photoactuation behavior of the self-folding box.

Movie S2 (.mp4 format). The walking behavior of the wormlike walking device

driven by an NIR light on and off (100 mW cm−2).

Movie S3 (.mp4 format). The worming behavior of the wormlike walking device

driven by an NIR light on and off (100 mW cm−2).

Movie S4 (.mp4 format). The turning behavior of the wormlike walking device

driven by an IR laser.

Movie S5 (.mp4 format). The grasping behavior of the “artificial/robotic hand”

driven by light irradiation.

Movie S6 (.mp4 format). The crawling behavior of the “microrobot” inside a

minipipe driven by an NIR light on and off (100 mW cm−2).

Supplementary Figures

Fig. S1. Schematic illustration of the MGM having a dual-gradient structure with vertical and lateral

gradients.

Fig. S2. XPS survey spectra of (A) GO-PDA/HI and (B) rGO. High-resolution C 1s spectra of (A) GO-

PDA/HI and (B) rGO.

Fig. S3. Powder XRD patterns of GO, GO-PDA, GO-PDA/HI, rGO, and graphite.

Fig. S4. Raman spectra of GO, GO-PDA, GO-PDA/HI, and rGO.

The degree of reduction of GO was characterized by powder XRD and Raman spectroscopy. The

powder XRD pattern of the prepared GO was compared with those of GO-PDA, GO-PDA/HI (GO-PDA

treated with HI) and rGO in fig. S3. Broad peaks near 10.27° and 24.57° were observed for the GO

powder and rGO powder, respectively1. Compared with rGO, the peak from GO-PDA/HI at 10.27° is

typical of GO, confirming incomplete reduction of GO on the GO-PDA surface. This result supports the

concept that PDA could protect GO from further reduction by HI. The fig. S4. presents the micro-

Raman spectra of powder samples of GO, GO-PDA, GO-PDA/HI and rGO. These spectra suggest that

DA has a slightly lower ability to reduce GO than HI and further indicates that PDA could protect GO

from reduction by HI2. These observations agree well with previous findings and the XRD analysis.

Fig. S5. Optical images show the adhesive tape–peeling method (top). SEM images of the border of

GO-PDA line after 0, 30 and 60 peeling actions indicate that the GO-PDA layer is hardly peeled off

from rGO layers.

Fig. S6. The gravimetric tensile strength of GO-PDA/rGO and rGO regions. The data were statistically

analyzed from 14 samples.

Fig. S7. (A and B) The thickness profiles of GO-PDA line with light on and off (3D images of GO-PDA

line performed by optical profiler). (C) Time-dependent weight measurements of the MGM and rGO

film under on/off irradiating. Insets show the paper (10×30 mm) deformation. It was irradiated for 2 s

and then allowed to cool to room temperature. (D) Attenuated total reflectance-infrared (ATR-IR)

spectra of the GO-PDA/rGO film show that the intensity of the hydroxyl stretching vibration of water

decreases with increasing temperature.

Fig. S8. The digital photograph of the moisture control device and the recovery performance tested at

different relative humidity environments. The MGM demonstrated a faster recovery with the increasing

of relative humidity.

Fig. S9. Schematic illustration of θ, γ, L, F, and ρ (L is the width of GO-PDA line; F is the stress

generated by GO-PDA line; ρ is the radius of curvature; θ is the bending angle of MGM; γ is the

supplementary angles of θ)

Fig. S10. Schematic illustration of the preparation of a self-folding box. I: the dual-gradient GO paper

was obtained after a mask-assisted filtration process; II: the obtained dual-gradient GO paper was

reduced by hydriodic acid (HI) and thoroughly washed under ambient laboratory conditions; III: the

self-folding box was obtained through laser cutting and patterning (or cut using scissors, but the laser

could control the clipping boundary better).

Fig. S11. The stress generated by the MGMs (middle and right) were measured on the universal testing

machine (Instron Model 5969) with on/off NIR light irradiations (left).

Fig. S12. Cross-sectional field-emission SEM images indicating GO-PDA/rGO regions for different

GO-PDA lines: (A) 1 mm, (B) 3 mm, and (C) 5 mm. (Insets show the samples used to test the stress.)

The thickness values measured here were used to calculate the cross sectional area.

Fig. S13. (A) Temperature-change curves of the MGM exposed to laser at a power density of 200 mW

cm-2. The temperature value is the average temperature measured from the irradiated area indicated in

fig. S12B. (B) Thermal image of the MGM before and after 2.2 s irradiation. (C) The lifting distance,

maximum speed (v), and period in the experiment where the maximum energy conversion efficiency and

power density were calculated (see Note S1). (D) Images of the MGM (3 mm GO-PDA line) lifting a

titanium foil by 7 mm within 3.2 s under 2.2 s laser irradiation.

Fig. S14. Cycle output test of MGM under on/off irradiations.

Fig. S15. Optical image of the walking behaviour of the walking device driven by NIR light.

Fig. S16. (A) Optical images showing the turning behavior of the walking device. (B) Temperature

change of different areas of the walking device as laser light is turned on (time, 0.7 s) and off (time,

1.1s).

Fig. S17. Turning angle of the walking devices as a function of time as light is turned on and off for

different illumination areas. The turning direction of the walking device could be controlled by

irradiation regions. The walking devices would turn to a certain side when the laser irradiated one side

(+). It would turn to the opposite direction (-) if the other side was irradiated.

Fig. S18. Optical images show the walking device progressing over a virtual map driven by light

irradiation (scale bar, 3 cm). And this figure depicts a demonstration of the worm like walking device

completing various bending and stretching actions (a simple demonstration of ‘the story of Three

Kingdom’ of ancient China). The ‘worm’ started from Wei's country, then reached Shu’s country after

several bend and stretch behaviors. In the Shu’s country, the ‘worm’ completed a turning and walked to

Wu’s country step by step. At last the walking device came back to Wei’s country.

Fig. S19. The schematic illustration and optical image showing the measurement of the bending angle

using a laser displacement sensor. The Eq. θ = 180°-arc tan(d/c) given in this figure was used to

calculate the bending angle. The height c is a fixed value. The d can be measured at 10 μm resolution

using laser displacement sensor and ruler. Therefore the resolution of calculated angle values is at least

at 0.1°.

Table. S1 Maximum output stress, bending angle, and theoretical bending angle as a function of GO-

PDA width (average value of data).

GO-PDA width

(mm)

Tensile strength

(MPa)

Maximum bending angle

(°)

Theoretical bending angle

(°)

1 9 100 109.4

2 15 80 82.2

3 23 60 55

4 29 43 37.2

5 33 32 26.5

6 44 17 14.7

Supplementary Note S1: Calculations of the maximum energy conversion efficiency of our actuator:

The maximum energy conversion efficiency of our actuator is defined as the maximum work output

during material contraction divided by the input energy.

The input energy was estimated as the incident light energy:

Ein=Plaser St (1)

where Plaser is the light power (200 mW cm-2), S is the light facula area (7.63×10-2 cm2), and t is the

irradiation time (2.2 s). The input energy (Ein) is calculated to be 0.0336 J.

The maximum mechanical work MGM when lifting the titanium foil was approximated as:

Eout=movo2/2 +mogΔh (2)

where vo is the maximum speed of the object during uplift process (3.2 mm ms-1), Δh is the lifting

distance where the object showed maximum speed (2.5 mm), mo is the weight of the object (120 mg).

Eout was calculated to be 0.617×10-3 J.

At last, the efficiency (η) of the actuator (η = Eout/Ein × 100%) was calculated to be 1.8%.

The contraction finished at 3.2 s, this 1-mg actuator could deform and lift a 120 mg load to a height of 7

mm within 3.2 s. The power density (W) is calculated using:

W= mogΔh’/ma/t (3)

Where Δh’ is the largest lifting distance (7 mm), ma is the weight of the actuator, t is lifting time. W was

2.6 W kg-1.

Supplementary Methods

Raman spectra were recorded on a Renishaw in plus laser Raman spectrometer with λexc=785 nm. XRD

spectroscopy was carried out on a Rigaku D/max 2550 V X-ray diffractometer using Cu Kα irradiation

(λ=1.5406 Å). The operating voltage and current were kept at 40 kV and 300 mA, respectively.

Supplementary Movies

Movie S1. The photoactuation behavior of the self-folding box. A relatively low-power NIR light (100

mW cm-2) is incident from the right side of the scene.

Movie S2. The walking behavior of the wormlike walking device driven by an NIR light on and off (100

mW cm-2).

Movie S3. The worming behavior of the wormlike walking device driven by an NIR light on and off

(100 mW cm-2).

Movie S4. The turning behavior of the wormlike walking device driven by an IR laser. A relatively

high-power visible-near infrared laser radiation (200 mW cm-2) is incident from the one side to another

side.

Movie S5. The grasping behavior of the “artificial/robotic hand” driven by light irradiation.

Movie S6. The crawling behavior of the “microrobot” inside a minipipe driven by an NIR light on and

off (100 mW cm-2).