Self-restoring, waterproof, tunable microstructural shape memory triboelectric nanogenerator for self-powered water temperature sensor

Abstract

The thermal induced temporal changes of microstructured shape memory polymer for self-recovery triboelectric nanogenerator can be indigenously harnessed for water energy harvesting and water temperature sensing, simultaneously. Here, tunable microarchitectures of a thermally triggered shape memory polymer are realized by electrospinning, namely mats of microfibers (MFs), microspheres (MSs), and microspheres-nanofibers (MSNFs). The tunable microarchitectured shape memory triboelectric nanogenerators (mSM-TENG) exhibit self-restoring ability in both macro shape and micro morphology, while attaining enhanced and alterable triboelectric output (∼150–320 V, ∼2.5–4 μA cm−2) due to increased frictional effects enabled by the high surface roughness. Typically, the MFs mat is realized as a skin-contact-driven shape memory TENG, serving well as wearable power source due to variable temporary shapes that are realizable under heating. At the micro level, self-restoring capability enabled by thermal stimuli renders the deformed mats capable of restoring to the original microstructures, affording the durable TENGs with prolonged lifetime. By the aid of a cellulose oleoyl ester, waterproof mat based TENGs with retentive rough surface are attainable for harvesting energy from both cold and hot water. Accordingly, a deformed waterproof TENG is found to be recoverable in shape under hot water. The gradient surface roughness delivers distinguishable triboelectric outputs during the structural recovery process, enabling a water energy harvester with sensing ability for water temperature (25 ± 5 °C to 95 °C), promising for self-powered waterproof wearable electronics and smart wastewater management system.