Fig. 3 The material choices and durability of the STENG. The material choices and durability of the STENG. (A) Summarized peak amplitude (A) of VOC and (B) three representative VOC profiles (B) of a VHB-STENG with relative contact-separation motion to different materials. (C) Output VOC and QSC of a PDMS-STENG using PAAm-LiCl hydrogel with different LiCl concentrations. (D) Normalized weight retention of the PAAm-LiCl hydrogel, VHB-STENG, and PDMS-STENG kept at a dry environment with an RH of 30% at 30°C. (E) Comparison of the VOC of the PDMS-STENG before and after storing in the dry environment for 30 days. (F) ISC of a PDMS-STENG that lasted for ~5000 cycles of contact-separation motions (1 hour). Xiong Pu et al. Sci Adv 2017;3:e1700015 Copyright © 2017, The Authors