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Shin et al. Soft Sci 2024;4:22 https://dx.doi.org/10.20517/ss.2024.03 Page 3 of 13

EXPERIMENTAL
Materials
PEDOT:PSS (Heraeus Clevios PH1000) was purchased from Ossila. Polyethylene glycol 400 (PEG) was
obtained from Thermo Fisher Scientific. Dimethylsulfoxide (DMSO; > 99.9%), Tergitol 15-s-9 (tergitol),
toluene (> 99.5%), regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT; MW = 50,000-100,000), anhydrous
dichloromethane (DCM; > 99.8%), and gallium-indium eutectic (EGaIn) were acquired from Sigma Aldrich.
Polydimethylsiloxane (PDMS; Sylgard 184) came from Dow-Corning. Styrene-ethylene-butylene-styrene
(SEBS, G1657) was purchased from Kraton polymers. Tween 80 was obtained from Duksan Chemicals.
Fast-drying silver paint (160040-30) was purchased from Ted Pella.

Preparation of the soft PEDOT:PSS solution
The soft PEDOT:PSS electrode was prepared by initially mixing PEDOT:PSS with DMSO in a weight ratio
[23]
of 4% to enhance conductivity . This mixture was then blended with tergitol and PEG in a weight ratio of
100:1:8. Subsequently, the solution was stirred vigorously for 30 min at room temperature.

Preparation of the P3HT-NFs/PDMS composite solution
P3HT was dissolved in DCM to form a 4 mg/mL solution at 80 °C, then cooled at -25 °C for an hour to
yield P3HT-NFs [24,25] . The P3HT-NFs solution was mixed with PDMS in DCM (80 mg/mL) at a weight ratio
of 1:4, producing the P3HT-NFs/PDMS composite, which was then stored at -25 °C.

Preparation of the fully soft Schottky diode, bridge rectifier, and logic gates
The fully soft Schottky diode fabrication process began with preparing soft PEDOT:PSS electrodes. The soft
electrode was patterned by spin-casting the solution at 500 rpm for 60 s onto an ultraviolet-ozone (UV-O )
3
treated SEBS substrate using a polyimide-based shadow mask prepared with a Silhouette Portrait 3
programmable cutting machine. The patterned electrode was subsequently annealed at 100 °C for 30 min.
The P3HT-NFs/PDMS composite was then spin-casted onto the electrodes at 500 rpm for 60 s using a
polyimide-based shadow mask, followed by annealing at 100 °C for 30 min. EGaIn was applied to the
P3HT-NFs/PDMS layer using doctor-blading through a polyimide-based shadow mask. The device
fabrication process is schematically illustrated in Supplementary Figure 1. Depending on the type of device,
such as a bridge rectifier or logic gates, the soft resistor was fabricated by spin-casting P3HT-NFs/PDMS
between the lateral gaps of two soft PEDOT:PSS electrodes, following the same method.

Preparation of the skin-interfaced energy harvesting system
The energy harvesting system was constructed using a commercial PENG and a ceramic capacitor, which
were incorporated into the fully soft bridge rectifier. Copper electric cables and the silver paint were used
for interconnection to ensure electrical conductivity. For the skin-interfaced system, a soft dry-adhesive film
[26]
was prepared . This preparation involved mixing liquid state [10:1 (w/w) ratio of prepolymer to curing
agent] with 2.5 wt% Tween 80. To ensure a smooth and consistent adhesive capability, the mixture was
thoroughly degassed in a vacuum chamber. Afterward, the PDMS mixture was cast onto a glass slide and
placed in a convection oven at 60 °C for two hours, forming the soft dry-adhesive film. Lastly, the integrated
system was carefully positioned onto these prepared soft dry-adhesive films.

Characterization of the device and materials
The electrical properties of the fully soft Schottky diode were characterized using a Keithley 4200-SCS
semiconductor analyzer, Keysight B2912B, and an LCR meter (E4980A, Keysight Technology Inc.) under
mechanical strain, employing a customized stretcher and programmable stretching machine (Bending &
Stretchable Machine System, SNM Korea). The rectifiers and OR and AND logic gates were characterized
with a RIGOL DG4102 function generator and GW Instek GPP-3323 DC power supply. The output voltage