Tannery solid waste-derived cross-scale deformable piezoresistive sensors for monitoring human body motions†
Abstract
Tannery solid wastes (TSWs) generated in tanneries during the leather manufacture process mainly contain collagen fibers with a hierarchical fiber structure, which are potential low-cost raw materials for preparing piezoresistive sensors. Herein, we developed cross-scale deformable piezoresistive sensors that were prepared from TSWs derived conductive foam with a pillars-supported directional multi-layer (PSDM) structure. The structural hierarchy of TSWs provides cross-scale structural deformations at both the nanoscale and microscale for accomplishing sensitive monitoring under both low and high pressure stimuli, while the surface contacts of directional layered architecture enabled by the PSDM structure allow for the sensitive monitoring of large scale deformations in the microscale range. Therefore, the as-prepared cross-scale deformable piezoresistive sensors were able to recognize a variety of human body motions, including breathing patterns (e.g. normal breath, deep breath and fast breath), body motion patterns (e.g. walking and jumping) and sitting postures (e.g. straight and bending). Benefiting from the high porosity of the PSDM structure (92.42%), the piezoresistive sensors also provided high water vapor permeability (90.76 g mm m−2 h−1 kPa−1) guaranteeing good wearability. Our investigations demonstrated a new approach for resource utilization of TSWs generated from tanneries, which also provided a new conceptual idea for developing piezoresistive sensors with good wearing comfortability and sensory capability.