纤维素纳米纤维水凝胶在自供能可穿戴压力传感领域的研究进展

Advances in cellulose nanofiber hydrogels for self-powered wearable pressure sensors

现有的压力传感器无法解决对人体信号长期监测过程中的供能问题,需要频繁地充电甚至更换电池,给传感器的检测过程带来了极大的不便。此外,压力传感器本身的柔韧性以及与人体皮肤的贴合程度对传感性能有着较大程度的影响。水凝胶因其可调节的模量和对人体皮肤的良好顺应性,适合作为柔性可穿戴压力传感材料。同时,纤维素纳米纤维是自然界储备量极大的生物质高分子材料,具有良好的生物可降解性和机械性能,通过对其进行化学改性,可以获得良好的压电以及摩擦电响应性能。笔者综述并探讨了利用纤维素纳米纤维基水凝胶制造具有自供电能力的柔性传感器的最新进展。首先简要介绍了纤维素纳米纤维;接着概述了基于纤维素纳米纤维的水凝胶的物理与化学交联策略;随后介绍了其在柔性压电、摩擦电压力传感器的工作原理和实际应用;最后提出了基于纤维素纳米纤维的柔性自供电压力传感器发展的挑战和前景。总结认为,纤维素纳米纤维基水凝胶具有优异的传感性能、机械柔韧性、贴合性以及生物可降解性,是构筑柔性自供电压力传感器的理想材料。

The 21st century has seen rapid advancements in the field of flexible electronics field.Unlike traditional pressure sensors,flexible pressure sensors are lightweight,portable,and comfortable,making them a focal point of widespread interest.Despite these advantages,the issue of discontinuous energy supply during long-term monitoring of complex physiological signals in the human body remains unresolved.Flexible pressure sensors often require frequent charging or battery replacement,leading to signal detection interruptions and complicating the sensing process.Therefore,it is crucial to develop self-powered flexible pressure sensors that can harvest energy from environmental sources or the human body.Moreover,the flexibility of the pressure sensor and the degree of adhesion to the human skin have a great influence on the sensing performance.Hydrogels are three-dimensional network structures that are physically or chemically crosslinked,consisting mostly of water,with water content that can exceed 90%.The network density of the hydrogel network is controlled by crosslinking points,and it is a key factor affecting the mechanical properties of hydrogels.Therefore,hydrogels exhibit adjustable mechanical performance.During the compression process under external force,hydrogels undergo deformation through the sliding of polymer chains,which contributes to their flexibility.Hydrogels are ideal materials for flexible,wearable pressure sensing materials due to their adjustable modules and excellent compatibility with human skin.At the same time,cellulose nanofibers are natural biomass polymers,which are abundantly available on earth.They have good biodegradability and mechanical properties.Chemical modification of cellulose nanofiber can enhance the piezoelectric and triboelectric responses.Therefore,cellulose nanofiber-based hydrogels provide excellent sensing capabilities,mechanical flexibility,adhesion property,and biodegradability,making them ideal materials for developing flexible self-powered pressure sensors.This review summarizes recent development of flexible pressure sensors with self-powered capability based on cellulose nanofiber-based hydrogels.First,a brief introduction to the construction,microstructure and properties of cellulose nanofibers is provided,followed by an overview of the physical and chemical cross-linking strategies used in cellulose nanofiber-based hydrogels.Physical crosslinking includes hydrogen bonds,hydrophobic interactions,electrostatic interactions,and ionic interactions.Chemical crosslinking can be categorized into conventional chemical crosslinking and dynamic chemical crosslinking(such as borate ester bonds and disulfide bonds).Subsequently,flexible self-powered pressure sensors based on cellulose nanofiber hydrogels can be classified into piezoelectric and triboelectric types according to their energy supply mechanisms.Their working principles and practical applications in detecting human signals are discussed.Finally,the challenges and prospects for the development of flexible self-powered pressure sensors based on cellulose nanofibers are summarized.