Supplementary Information

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1 Supplementary Information Tough Nanocomposite Ionogel-based Actuator Exhibits Robust Performance Xinhua Liu 1, Bin He 2 *, Zhipeng Wang 2, Haifeng Tang 2, Teng Su 1, and Qigang Wang 1 * 1 Department of Chemistry and Advanced Research Institute, Tongji University, Shanghai (P. R. China) 2 Department of Control Science and Engineering, Tongji University, Shanghai (P. R. China) Contents Index Page 1. Materials... S2 2. Alternating Current Impedance Spectroscopy... S2 3. Displacement Simulative Equation... S3 4. Frequency Simulative Equation... S4 5. Simulative Equation with load... S5 6. References... S6 7. Table... S6 8. Figures... S7 1

2 1. Materials. 1-butyl-3-methylimidazolium tetrafluoroborate was obtained from Lanzhou Institute of Chemical Physics (The Chinese Academy of Sciences). TiO 2 was purchased from Dekedaojin (Beijing) Co., Ltd. 2-Hydroxyethyl Methacrylate was purchased from Shanghai Energy Chemical Co., Ltd. Activated charcoal powder (YP80F, surface area of 2100 m 2 /g) was purchased from Kuraray Co., Ltd. Polytetrafluoroethylene and acetylene black were obtained from Aladdin and Shanghai 3F New Co. 2. Alternating Current Impedance Spectroscopy The activated charcoal powder was acquired from Kuraray Co. The electrochemical properties were performed out by a Metrohm Autolab PGSTA302N potentiostats-galvanostats (The Netherlands) coupled with a computer. As for the AC impedance measurements, the BMIMBF 4 based ionogel samples were SS/electrolyte/SS sandwiched structured with a PTFE spacer with a circular hole for holding the gel electrolyte and were placed in a water-controlled furnace (stainless steel electrode: SS). The measurements were taken over the frequency range of 100 khz to 10 mhz. The ionic conductivity of the electrolyte was evaluated with the help of nova 1.10 software. The bulk resistance of the polymer electrolyte, R b, can be estimated from the fitting procedure, and correspondingly the conductivity of the gel polymer electrolyte is calculated according to Equation σ=l/(ar b ) where l is the thickness of the gel electrolyte and A is the area of stainless steel electrode. In the present study, the semicircular portion disappeared, indicating that 2

3 the current carriers are ions and hence the total conductivity is the result of ionic conduction. [S1] The resistance of the bulk electrolyte has been retrieved from the intercept of the straight line on the real axis. [S2] 3. Displacement Simulative Equation From a geometric approach, the volume difference of the actuator can be ideally calculated as follows: Based on the volume change of the transferring ions, we can ideally calculate the volume difference: Then, the rotating angel can be described by the following Equation Hence, the displacement can be described by the following Equation: [Equation S1] where D is the displacement, L is the free length of the actuator, U is the applied voltage, W is the thickness of the actuator, Csp is the specific capacitance of the supercapacitor-like actuator, ρ is the density of the activated carbon, t is the thickness of the activated carbon film, w is the width of the actuator, is the volume of the cation, and is the volume of the anion. 3

4 4. Frequency Simulative Equation To test the frequency response characteristic of the ionogel, an experimental system was established. The system consists of a signal generator (Agilent 33500B Series Waveform Generator, Agilent Technologies Inc.) and a power amplifier (HEA-200C, Nanjing Funeng Co., Ltd.). The signal generator output a standard sinusoidal waveform (the peak voltage is 4.7 V) with preset frequency, which was amplified by power amplifier to drive the ionogel. And then the terminal displacement of the ionogel can be measured according to the coordinate paper. Signal Generator Power Amplifer Ionogel The generated strain (ε) was calculated according to the Equation: where W is the thickness of the actuator, D is the displacement, and L is the free length of the actuator. Since the actuator can be equivalent to a simple RC circuit, AC R C the impedance of the capacitor can be written as: 4

5 where, f is the frequency of AC input voltage (sinusoidal wave for example). C is the capacitance. Then, the voltage applied to the capacitor can be expressed as: where, U is the voltage value of input signal. The quantity of electricity of the capacitor is given as: [Equation S2] 5. Simulative Equation with Load The actuator can be molded as a cantilevered bender; the schematic representation for ionogel is as followed: M y u M G x G According to literature, [S3] ionogel can be molded as a cantilevered bender. The driven moment can be expressed as: where, α is the electromechanical transfer coefficient. Uc is the voltage applied to the ionogel. C is the capacitance of the ionogel. h 1 and h 2 are the distances from 5

6 neutral axis to the surfaces of ionogel and active carbon respectively. L is the length of the ionogel. As described in literature, [S4] for small deflections, the bending moment of ionogel in y axis can be represented as: where, E is the Young s modulus. I is the area moment of inertia of the bender s cross section. C and D are constants of integration. M d is bending moment, which can be written as: [S3] where, M is the driven movement, M G is the moment caused by the gravity of load. 6. References [S1] J. Malathi, M. Kumaravadivel, G. Brahmanandhan, M. Hema, R. Baskaran, S. Selvasekarapandian, J. Non-Cryst. Solids 2010, 356, [S2] S. Rajendran, O. Mahendran, R. Kannan, J. Phys. Chem. Solids 2002, 63, 303. [S3] J. Gere, ISBN , Cheltenham, UK, [S4] G. Alici, B. Mui, C. Cook, Sens. Actuators, A: Physical 2006, 126, Table: Table S1. The mechanical properties of the ionogels No. TiO 2 /HEMA Compressive strength (kpa) Compressive modulus (kpa) Tensile strength (kpa) Tensile modulus (kpa) 1 0.2/ ± ± ± ± / ± ± ± ± / ± ± ± ± / ± ± ± ±

7 8. Figures: Figure S1. TGA-curves of the reaction mixtures with different time of UV-radiation. (a) 0 min; (b)15 min; (c)30min; (d) 45 min; (e)60 min; (f) The conversion of HEMA monomer estimated by TGA-curves. Figure S2. Tensile test of the ionogels with different TiO 2 contents. 7

8 Figure S3. The frequency dependent impedance plots of BMIMBF 4 based gel electrolyte. Figure S4. Cyclic voltammograms of ionogel based actuator at different sweep rates. 8

9 Figure S5. Photographs of the actuator with 1.5 times additional mass loading besides the original weight under an applied voltage of ±3.5 V. Figure S6. High temperature driving performance (100 ) of ionogel based actuator under applied voltage of ±3.5 V. Figure S7. Low temperature driving performance (-10 ) of ionogel based actuator under applied voltage of ±3.5 V. 9