Pdda solution

PDDA-MWCNTs solution (1 g/L) was prepared by adding MWCNTs (1 mg) to PDDA solution (1 mL, 10 g/L; Sigma, SAINT LOUIS, MO, USA), followed by sonication for 60 min to form a homogenous dark solution, which was kept at room temperature for 24 h, filtered, and then stored at 4 °C until further use.

SUS316L stainless steel substrate was purchased from Sinkang Industries Co., Ltd., (New Taipei City, Taiwan). Graphite powder was purchased from Allightec Co., (Taichung City, Taiwan). 3,4-Ethylenedioxythiophene (EDOT), PSS solution (Mw 75,000 g/mol), hydrogen peroxide (H₂O₂), hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃), sodium chloride (NaCl), alcohol, potassium permanganate (KMnO₄), and PDDA solution were purchased from Sigma-Aldrich Corp. (St. Louis, MO, USA) and Acors Organics (Ozaukee County, WI, USA).

Graphite powder, potassium permanganate, sulfuric acid, sodium nitrate, hydrogen peroxide, ammonium persulfate, aniline, PDDA solution, Nafion 117 solution, trichloro(1H,1H,2H,2H‐perfluorooctyl)silane, hydrochloric acid, and other chemicals were purchased from Sigma‐Aldrich (Buchs, Switzerland) and used as received. Polyimide films with a thickness of 125 µm were also purchased from Sigma‐Aldrich. Silver Flake Ink (Metalon HPS‐021LV) was purchased from Novacentrix (Austin, USA). Polymer aluminum capacitors were purchased from Mouser Electronics (Munich, Germany). The Joy‐it SBC‐LCD 16 × 2 display module (HD44780) (cat. no. 1 503 825), L10 Solar Garden Light (0.2 W, SMD LEDs; cat no. 2 497 614), and Philips GU5.3 12 V/3.5 W/200 lumen LEDspot Light (Philips) were purchased from Conrad Electronics AG (Wollerau, Switzerland). The rechargeable lithium polymer battery (3.7 V/600 mAh) was purchased from RS PRO (cat. no. 176–9379; RS PRO, Wädenswil, Switzerland).