30 s Response Time of K+ Ion-Selective Hydrogels Functionalized with 18-Crown-6 Ether Based on QCM Sensor - Zhang, Z; Dou, Q; Gao, H; Bai, B; Zhang, Y; Hu, D; Yetisen, AK; Butt, H; Yang, X; Li, C; Dai, Q (ADVANCED HEALTHCARE MATERIALS, 2018)