With the development of technology and the improvement of living standards, wearable electronic devices have attracted more attention. Here, both stretchable and compressible hydrogel strain sensors based on carbon nanofiber powder (CFP) and polyvinyl alcohol (PVA) are prepared by freezing–thawing cycles. The PVA/CFP hydrogel exhibits excellent stretchable (366%) and compressible strains (70%). During 1000 loading–unloading cycles, the PVA/CFP hydrogel has a low plastic deformation (<10%, for both stretching and compressing), small energy loss efficiency (5.62% under stretching and 12.13% under compressing), and stable mechanical strength and excellent sensitivity, at conditions whether it is stretched to 100% or compressed to 50% strains. The stretchable and compressible PVA/CFP hydrogel can not only accurately detect multiple stretching behaviors of human activity, such as bending of joints, swallowing or breathing, but also detect the changes of pressure during walking. Besides, the PVA/CFP hydrogel can operate electronic screens due to its internal ions, with more potential application in soft robotics and electronic skin.

中文翻译：

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高度可拉伸和可压缩的碳纳米纤维-聚合物水凝胶应变传感器，用于人体运动检测

随着技术的发展和生活水平的提高，可穿戴电子设备引起了越来越多的关注。在这里，基于碳纳米纤维粉末（CFP）和聚乙烯醇（PVA）的可拉伸和可压缩水凝胶应变传感器都是通过冻融循环制备的。PVA / CFP水凝胶具有出色的可拉伸性（366％）和可压缩应变（70％）。在1000次装卸循环中，PVA / CFP水凝胶的塑性变形低（拉伸和压缩均<10％），能量损失效率低（拉伸时为5.62％，压缩时为12.13％），并且机械强度和在拉伸至100％或压缩至50％应变的条件下均具有出色的灵敏度。可拉伸和可压缩的PVA / CFP水凝胶不仅可以准确地检测人类活动的多种拉伸行为，例如关节弯曲，吞咽或呼吸，还可以检测步行过程中的压力变化。此外，PVA / CFP水凝胶由于其内部离子而可以操作电子屏幕，在软机器人和电子皮肤中具有更大的潜在应用。