Peel-Transferable Omnidirectional Strain Sensor Via Screen-Printed MWCNT-OH/Ecoflex and Spray-Coated c-MOF/PEDOT Functional Layers.

Omnidirectional strain sensors capable of detecting large and complex deformations are highly promising for wearable motion monitoring; however, achieving both multidirectional strain perception and enhanced electrical sensitivity remains challenging. Herein, a peelable circular piezoresistive strain sensor based on KH570-modified hydroxylated multi-walled carbon nanotubes (m-MWCNT-OH)/Ecoflex is developed through a screen-printing strategy and further functionalized with a copper (II) 2,3,6,7,10,11-hexahydroxytriphenylene (Cu3(HHTP)2) conductive metal-organic framework (c-MOF)/poly(3,4-ethylenedioxythiophene) nanofiber (PEDOT-NFs) nanolaminate. The circular sensing architecture facilitates uniform strain distribution and orientation-independent strain transfer, while the c-MOF/PEDOT-NFs coating constructs additional conductive pathways, enhancing strain-induced resistance variation. The sensor is fabricated using a sequential process involving screen printing of the m-MWCNT-OH/Ecoflex sensing layer, peel transfer, and spray deposition of the functional coating. The resulting sensor demonstrates a wide strain detection range of 0%-300%, a gauge factor (GF) of 8, a fast response time of 33 ms, a recovery time of 420 ms, and stable performance over 10 000 loading-unloading cycles. Compared with unmodified sensor, c-MOF/PEDOT-NFs functionalization significantly improves electrical sensitivity while maintaining the intrinsic omnidirectional sensing capability. Finite element analysis (FEA) confirms similar strain-transfer characteristics under different loading directions. The sensor enables accurate monitoring of multidirectional human motions, highlighting its potential for wearable electronics, soft robotics, and human-machine interfaces.