Bioinspired 3D Printable, Self-Healable, and Stretchable Hydrogels with Multiple Conductivities for Skin-like Wearable Strain Sensors

Bioinspired
hydrogels have promising prospects in applications
such as wearable devices, human health monitoring equipment, and soft
robots due to their multifunctional sensing properties resembling
natural skin. However, the preparation of intelligent hydrogels that
provide feedback on multiple electronic signals simultaneously, such
as human skin receptors, when stimulated by external contact pressure
remains a substantial challenge. In this study, we designed a bioinspired
hydrogel with multiple conductive capabilities by incorporating carbon
nanotubes into a chelate of calcium ions with polyacrylic acid and
sodium alginate. The bioinspired hydrogel consolidates self-healing
ability, stretchability, 3D printability, and multiple conductivities.
It can be fabricated as an integrated strain sensor with simultaneous
piezoresistive and piezocapacitive performances, exhibiting sensitive
(gauge factor of 6.29 in resistance mode and 1.25 kPa–1 in capacitance mode) responses to subtle pressure changes in the
human body, such as finger flexion, knee flexion, and respiration.
Furthermore, the bioinspired strain sensor sensitively and discriminatively
recognizes the signatures written on it. Hence, we expect our ideas
to provide inspiration for studies exploring the use of advanced hydrogels
in multifunctional skin-like smart wearable devices.

仿生水凝胶（Bioinspired hydrogels）因具备类似天然皮肤的多功能传感特性，在可穿戴设备、人体健康监测设备以及软体机器人等领域拥有极具潜力的应用前景。然而，制备可同时反馈多种电子信号（如受外部接触压力刺激时，模拟人体皮肤受体功能）的智能水凝胶，仍是一项重大挑战。本研究中，我们通过将碳纳米管（carbon nanotubes）掺入钙离子（calcium ions）与聚丙烯酸（polyacrylic acid）、海藻酸钠（sodium alginate）的螯合物中，设计出一种具备多重导电性能的仿生水凝胶。该仿生水凝胶兼具自修复（self-healing）能力、拉伸性能（stretchability）、3D打印性能（3D printability）与多重导电特性。该材料可被制备为集成型应变传感器，可同时实现压阻型（piezoresistive）与压电容型（piezocapacitive）传感性能，对人体细微压力变化（如手指屈曲、膝盖屈曲以及呼吸活动）展现出灵敏响应：电阻模式下灵敏因数（gauge factor）为6.29，电容模式下灵敏度为1.25 kPa⁻¹。此外，该仿生应变传感器可灵敏且具有区分度地识别书写于其表面的笔迹特征。因此，我们期望本研究思路可为探索先进水凝胶在多功能类皮肤智能可穿戴设备中的应用研究提供灵感与借鉴。