Electrothermally Triggered Broadband Optical Switch Films

Transcription

1 Supporting Information Electrothermally Triggered Broadband Optical Switch Films with Extremely Low Power Consumption Ryohei Yoshikawa, Mizuki Tenjimbayashi, and Seimei Shiratori* Center for Material Design Science, School of Integrated Design Engineering, Keio University, Hiyoshi, Kohoku-ku, Yokohama, Kanagawa , Japan S-1

2 MATERIALS AND METHODS Poly(vinyl butyral) (PVB, Mw=40,000-70,000; Sigma-Aldrich, St. Louis, MO), tin chloride (SnCl 2 ; Sigma-Aldrich), and ethanol (Kanto Chemical Co. Inc., Tokyo, Japan) were used in the preparation of the electrospinning solution. A poly(ethylene terephthalate) (PET) film with a thickness of 188 µm (Toyobo Co., Ltd., Osaka, Japan) was used as the substrate. Palladium chloride (PdCl 2 ; Sigma-Aldrich), and hydrochloric acid (HCl, conc.=37%; Wako Pure Chemical Industries Ltd., Osaka, Japan) were used for the preparation of an activation solution. Deionized water (DIW) that was purified using automatic water distillation apparatus (Advantec, Tokyo, Japan) was used in all experiments. Cu(II) sulfate pentahydrate (CuSO 4 5H 2 O), nickel (II) sulfate hexahydrate (NiSO 4 6H 2 O), sodium phosphinate monohydrate (NaPH 2 O 2 H 2 O), sodium citrate (Na 3 C 6 H 5 O 7 ), and sodium acetate (CH 3 COONa), which were used for the preparation of an electroless plating bath, were purchased from Wako Pure Chemical Industries Ltd. Sodium hydroxide (NaOH; 5N, Junsei Chemical Co., Ltd., Tokyo, Japan) was used as a ph adjuster. Paraffin (m.p.:42 44 C; Wako Pure Chemical Industries Ltd.), liquid paraffin (Wako Pure Chemical Industries Ltd.), cyclohexane (Wako Pure Chemical Industries Ltd.), and a PDMS gel precursor (Sylgard 184 silicone elastomer kit; Dow Corning, Toray Co., Ltd., Tokyo, Japan) were used to prepare the M-PW/PDMS solution. S-2

3 Fabrication of the Cu/Ni transparent heater Fabrication of the nanofiber template. The electrospinning solution was prepared by mixing 8 wt.% of PVB and 9 wt.% of SnCl 2 in ethanol by stirring at room temperature (RT) for 12 h. The resulting solution was then loaded into a hypodermic syringe (volume: ~1 ml; Terumo Co., Tokyo, Japan) with a needle (diameter = 0.80 mm; Terumo Co.). The syringe was then placed on a syringe pump stage to control the flow rate at 0.1 ml/h. The positive and ground terminals of a power supply were connected to the needle and to a drum collector (diameter = 9 cm), respectively. A PET film was then attached to the drum collector. The needle tip-to-collector distance was set at 10 cm. The drum collector rotation speed was fixed at a target value (50 rpm or 1500 rpm). Then, 12 kv was applied using the power supply for 90 s to deposit the nanofibers on the PET film. Activation process. The activation process is similar to that described in our previous report. The activation solution was prepared by dissolving PdCl 2 (1.0 g/l) and 2.0 mm HCl in DIW. The nanofibers that were deposited on the PET film were immersed in the activation solution for 10 min. The film was subsequently rinsed using DIW. Electroless plating. The plating bath was composed of ion sources, a reducing agent, a complexing agent, and a buffer agent. CuSO 4 5H 2 O (0.016 M) and NiSO 4 6H 2 O (0.038 M) S-3

4 were used as the Cu(II) and Ni(II) ion sources, respectively. NaPH 2 O 2 H 2 O (0.094 M) was used as the reducing agent. Na 3 C 6 H 5 O 7 (0.090 M) and CH 3 COONa (0.12 M) acted as the complexing agent and the buffer agent, respectively. All components of the plating bath were dissolved in DIW by stirring for 12 h. The ph of the bath was then adjusted to 10 by addition of NaOH. The rinsed templates were immersed in the plating bath at 70 C while stirring at 150 rpm for various plating times (180, 300, and 420 s). Fabrication of the M-PW/PDMS Solid paraffin was heated to 60 C and the solid and liquid paraffins were mixed at a volume ratio of 1:2 to prepare the mixed paraffin. A specified amount of mixed paraffin was dissolved in 0.9 g of cyclohexane and stirred at RT for 10 min. When the mixed paraffin was sufficiently dissolved and the solution became transparent, 1.8 g of the PDMS gel precursor and 0.1 g of the curing agent were added and the resulting mixture was stirred at RT for 5 min, followed by further stirring at 60 C for 3 min. Stirring was then stopped and the mixture was heated at 60 C to remove the bubbles from the solution. Finally, 0.3 g of the solution was cast on the PET film or the transparent heater and heated at 60 C for 3 h. Characterization The film geometry was characterized using field emission scanning electron microscopy S-4

5 (FE-SEM; Hitachi, Tokyo, Japan) with an accelerating voltage of 5 kv. The sheet resistance was measured via the standard four-probe method using a Loresta GP resistivity meter (MCP-T610, Mitsubishi Chemical Analytech, Co., Ltd., Kanagawa, Japan). An ultraviolet-visible (UV-vis) spectrophotometer (UV-3600 Plus, Shimadzu, Kyoto, Japan) and a haze meter (NDH-5000, Nippon Denshoku Industries, Tokyo, Japan) with a white light-emitting diode acting as a light source were used for measurement of the optical properties. The PET film was used as a reference film in the above optical properties measurements. The temperature-dependent optical transmittance was measured using another UV-vis spectrophotometer (UV-2500 PC, Shimadzu). A differential scanning calorimeter (DSC-60, Shimadzu) was used for the melting point measurements. To evaluate the heating characteristics of the aligned networks (dimensions: mm), a two-terminal side-contact configuration was constructed using silver paste (DOTITE D-500, Fujikura Kasei Co., Ltd., Tokyo, Japan). The surface temperature during application of the direct current voltage was measured using an infrared camera (PI1400, Optris GmbH, Berlin, Germany). S-5

6 Figure S1. A schematic of fabrication procedure of a M-PW/PDMS on a transparent heater. Figure S2. Cross-sectional SEM images of M-PW10/PDMS. The paraffin particles were uniformly dispersed within the PDMS gel networks in each area. S-6

7 Figure S3. Surface morphologies of M-PW10/PDMS: (a) as-prepared M-PW10/PDMS, and (b) M-PW10/PDMS after heating. The morphology was maintained after heating for transmittance switching because of the stable immobilization process. Table S1. The required energy quantities for transmittance switching of maximum width (The energy quantities were calculated based on the power densities and required times for switching which are provided in each literature). / / ref S S S S this work :power. :film area. :power density. t:required time for switching. E:energy. S-7

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