Ultrathin, breathable, swelling-resistant bio-mimetic electronic skin based on PVA/cellulose nanofibers for wearable devices and flexible bioelectronics.

In recent years, hydrogels have attracted significant attention for their potential in flexible sensors. However, the development of multifunctional hydrogel-based sensors remains challenging due to inadequate mechanical properties and limited breathability, which restrict their use in wearable devices. To overcome these limitations, this study presents an innovatively designed PVA/CNF/MXene (DS-PCM) ultrathin hydrogel film (126.8 ± 2.1 μm) with outstanding breathability, high stretchability, and excellent swelling resistance, making it highly suitable for wearable multifunctional sensors. The Hofmeister effect is leveraged to induce self-assembly, while directional freezing is employed to create a unique layered structure. Notably, salting-out treatment transforms weak hydrogen bonds between molecular chains into strong hydrogen bonds, significantly enhancing the hydrogel's tensile properties and achieving a remarkable stretchability of 790 %. The hydrogel also maintains its structural integrity and mechanical strength after 7 days of swelling. Additionally, the film exhibits exceptional breathability (2516.7 ± 102.5 g m d), excellent water retention, and high sensitivity to temperature variations (TCR = 3.67). Its seamless skin adhesion makes it superior to commercially available electrodes for physiological signal acquisition. These outstanding properties provide new insights into the design of multifunctional electronic skin.