Jeong Hwan Lee

Shape memory polymer-based self-healing triboelectric nanogenerator

Recently, triboelectric nanogenerators (TENGs) have received increasing interest due to their large potential for mechanical energy harvesting. Important progress has been achieved in increasing the output power and efficiency while new structures have emerged. In particular, their robustness and endurance have increased, but some critical concerns still remain about the degradation and lifetime of TENGs. How will TENGs age under intensive use in our daily lives? To address this issue, we propose in this paper to use shape memory polymers (SMPs) to extend TENGs’ lifetimes and guarantee their performance. For this purpose we introduce a new smart SMP-based self-healing TENG which has the capacity to be healed and to recover good performance after degradation of its triboelectric layer. We studied the degradation and healing process of the SMP–TENG, and the improvement in its endurance and lifetime, and thus demonstrate the huge potential of self-healing SMP–TENGs.

Triboelectrification-Induced Large Electric Power Generation from a Single Moving Droplet on Graphene/Polytetrafluoroethylene

Recently, several reports have demonstrated that a moving droplet of seawater or ionic solution over monolayer graphene produces an electric power of about 19 nW, and this has been suggested to be a result of the pseudocapacitive effect between graphene and the liquid droplet. Here, we show that the change in the triboelectrification-induced pseudocapacitance between the water droplet and monolayer graphene on polytetrafluoroethylene (PTFE) results in a large power output of about 1.9 μW, which is about 100 times larger than that presented in previous research. During the graphene transfer process, a very strong negative triboelectric potential is generated on the surface of the PTFE. Positive and negative charge accumulation, respectively, occurs on the bottom and the top surfaces of graphene due to the triboelectric potential, and the negative charges that accumulate on the top surface of graphene are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet.