Multifunctional Biomimetic e-Skin Constructed In Situ on Tanned Sheep Leather as a Multimodal Sensor for the Monitoring of Motion and Health

Bionic electronic skin, with its integrated biological functions, is capable of sensing and responding to external stimuli, potentially surpassing the ideal flexibility of natural skin in certain aspects. Most current preparation strategies employ the "bottom-up" approach, using various monomers or polymer materials to construct artificial networks through physical or chemical cross-linking, leading to issues of complexity and limited performance. In this work, we adopted a "top-down" strategy, in which the collagen fiber network of natural aluminum-tanned sheepskin was utilized as a scaffold to load monomers itaconic acid (IA) and hydroxyethyl acrylate (HEA). The subsequent in situ polymerization of IA and HEA led to the formation of poly(itaconic acid-co-hydroxyethyl acrylate) (P(IA-HEA)) and its filling among sheepskin collagen fiber skeleton, which results in the successful fabrication of a high-strength bionic electronic skin based on natural sheepskin (LIHEZ). The advantage of this approach is that it can retain the structure and properties of natural sheepskin and give the resulting LIHEZ multiple functions (e.g., electrical conductivity, adhesion, bacteriostasis, biocompatibility, and environmental stability), thereby replicating or even surpassing the performance of natural animal skin. LIHEZ demonstrated sensitive stimulus responsiveness and durability and could serve as multimodal sensors (strain, temperature, humidity, and bioelectricity) to efficiently monitor various human movements, physiological signals, and changes in environmental temperature and humidity. This diversified data collection provides reliable assurance for monitoring human health. The present construction method using sheepskin as the substrate not only breaks the conventional strategies and single applications but also provides new insights for the selection of flexible device substrates, promising to be a next-generation ideal material for constructing intelligent bionic electronic skin.