The development of wearable electronics, point-of-care testing, and soft robotics requires strain sensors that are highly sensitive, stretchable, capable of adhering conformably to arbitrary and complex surfaces, and preferably self-healable. Conductive hydrogels hold great promise as sensing materials for these applications. However, their sensitivities are generally low, and they suffer from signal hysteresis and fluctuation due to their viscoelastic property, which can compromise their sensing performance. We demonstrate that hydrogel composites incorporating MXene (Ti₃C₂T _x ) outperform all reported hydrogels for strain sensors. The obtained composite hydrogel [MXene-based hydrogel (M-hydrogel)] exhibits outstanding tensile strain sensitivity with a gauge factor (GF) of 25, which is 10 times higher than that of pristine hydrogel. Furthermore, the M-hydrogel exhibits remarkable stretchability of more than 3400%, an instantaneous self-healing ability, excellent conformability, and adhesiveness to various surfaces, including human skin. The M-hydrogel composite exhibits much higher sensitivity under compressive strains (GF of 80) than under tensile strains. We exploit this asymmetrical strain sensitivity coupled with viscous deformation (self-recoverable residual deformation) to add new dimensions to the sensing capability of hydrogels. Consequently, both the direction and speed of motions on the hydrogel surface can be detected conveniently. Based on this effect, M-hydrogel demonstrates superior sensing performance in advanced sensing applications. Thus, the traditionally disadvantageous viscoelastic property of hydrogels can be transformed into an advantage for sensing, which reveals prospects for hydrogel sensors.

中文翻译：

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MXenes将水凝胶传感器的性能扩展到新的极限。

可穿戴电子设备，即时检验和软机器人技术的发展要求应变传感器具有高度灵敏，可拉伸的特性，能够顺应性地粘附到任意复杂的表面上，并且最好具有自修复性。导电水凝胶作为这些应用的传感材料具有广阔的前景。然而，它们的灵敏度通常很低，并且由于它们的粘弹性而遭受信号滞后和波动的影响，这会损害它们的感测性能。我们证明了掺入MXene（Ti ₃ C ₂ T _x ）的性能优于所有报道的用于应变传感器的水凝胶。所获得的复合水凝胶[基于MXene的水凝胶（M-水凝胶）]显示出优异的拉伸应变敏感性，其规变系数（GF）为25，这是原始水凝胶的十倍。此外，M-水凝胶显示出超过3400％的显着拉伸性，瞬时自我修复能力，优异的顺应性以及对包括人体皮肤在内的各种表面的粘附性。M-水凝胶复合材料在压缩应变（GF为80）下表现出比在拉伸应变下高得多的灵敏度。我们利用这种不对称应变敏感性与粘性变形（可自我恢复的残余变形）相结合，为水凝胶的传感能力增加了新的维度。所以，可以方便地检测水凝胶表面的运动方向和速度。基于这种效果，M-水凝胶在高级感测应用中显示出出众的感测性能。因此，传统上不利的水凝胶粘弹性可以转化为传感的优势，这揭示了水凝胶传感器的前景。