Adamantane plasma polymers: fluorine-free vacuum-processable triboelectric thin films for all-triboelectric nanogenerator configurations
Triboelectric nanogenerators (TENGs) are major drivers in on-site power generation for smart devices, enable self-powered sensors, and introduce novel catalytic processes. Here, we present the advantages of adamantane plasma layers as bivalently triboelectric surfaces capable of exhibiting both tribopositive and tribonegative character through simple modification of the synthesis conditions without the need for additives or functionalization. Fabrication facing or backfacing the plasma yields thin film polymers with different dielectric constants, Young's moduli, and secondary electron emission. The conformality, stability, and processability of the polymers enable direct implementation across solid-solid, solid-liquid, and hybrid piezo-triboelectric configurations. Additional texturization by buckling is shown to provide voltage and current outputs as high as 90 V cm2 and 0.6 uA for a 2.8 um (tribonegative) vs. 400 nm (tribopositive) combination. A maximum power density of 2.1 uW cm-2 is generated from salty droplets in a switch-electrode drop-TENG configuration employing a 500 nm-thick tribopositive adamantane polymer as the triboelectric surface. These layers have demonstrated outstanding durability, enabling more than 10^5 cycles in solid-solid nanogenerators and 10^4 droplet impacts in solid-liquid configurations. The synthetic method is environmentally friendly and industrially scalable, making the adamantane plasma polymer a reliable and competitive solution for thin film triboelectric materials.