School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150000, China; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
J Colloid Interface Sci. 2021 Mar;585:420-432. doi: 10.1016/j.jcis.2020.10.023. Epub 2020 Oct 13.
Flexible and wearable hydrogel strain sensors have attracted significant attention for human activity monitoring and electronic skins. However, it remains a great challenge to develop an integrated hydrogel strain sensor showing intrinsic adhesive performances, tunable mechanical and high strain-sensitive properties. Marine mussels show a superior capacity to adhere to various substrates (including organic and inorganic), while polycaprolactone (PCL) can be easily modified into crosslinkers with different degrees of functionality (bi-, tri-, and quadri-functional groups) to control the crosslinking density. Therefore, the developed mussel-inspired 3,4-dihydroxyphenyl-l-alanine acrylamide-polycaprolactone (l-DMA-PCL) hydrogels could address these issues and serve as the potential wearable strain sensors for biomaterials and healthcare monitoring.
l-DMA monomers were successfully crosslinked by functionalized PCL (bi-, tri-, and quadri-functional) using UV light (wavelength ~ 365 nm) to prepare the l-DMA-PCL hydrogel. Adhesive behaviors, tunable mechanical properties and strain sensing performances of the l-DMA-PCL hydrogels were systematically studied.
The l-DMA-PCL hydrogel exhibited reversible adhesion to various material substrates (including steel, aluminum, ceramics, poly(ethylene terephthalate) (PET), wood, rubber, even for polypropylene (PP) and polytetrafluoroethylene (PTFE)) as well as skin. Moreover, the mechanical properties (stress: 50.2-72.4 KPa, strain: 700-1140%, Young's modulus: 8.6-14.8 KPa, and toughness: 16.4-53.6 KJ/m) of the hydrogels could be readily tuned by the modulation of functionality degree (bi-, tri-, and quadri-functional) of PCL. Intriguingly, the hydrogel-based wearable strain sensor showing high conductivity (0.0550 S/cm) and sensitive responses to both large (e.g., joint bending) and subtle human motions (e.g., frowning and speaking). Based on these achievements, this work provides new insights into the development of hydrogel with adhesiveness, controllable mechanical performance and high strain sensitivity as a flexible and wearable hydrogel strain sensors.
可拉伸、可穿戴的水凝胶应变传感器因其在人体活动监测和电子皮肤方面的应用而受到广泛关注。然而，开发具有内在粘附性能、可调机械性能和高应变敏感性的集成水凝胶应变传感器仍然是一个巨大的挑战。贻贝具有优异的粘附各种基底（包括有机和无机基底）的能力，而聚己内酯（PCL）可以很容易地被修饰成具有不同功能度（双、三、四官能团）的交联剂，以控制交联密度。因此，所开发的受贻贝启发的 3,4-二羟基苯丙氨酸丙烯酰胺-聚己内酯（l-DMA-PCL）水凝胶可以解决这些问题，并作为潜在的可穿戴应变传感器用于生物材料和医疗保健监测。
使用功能化的 PCL（双、三、四官能团）通过紫外光（波长约 365nm）成功交联 l-DMA 单体，制备 l-DMA-PCL 水凝胶。系统研究了 l-DMA-PCL 水凝胶的粘附行为、可调机械性能和应变传感性能。
l-DMA-PCL 水凝胶表现出对各种材料基底（包括钢、铝、陶瓷、聚对苯二甲酸乙二醇酯（PET）、木材、橡胶，甚至聚丙烯（PP）和聚四氟乙烯（PTFE）以及皮肤）的可逆粘附性。此外，水凝胶的机械性能（应力：50.2-72.4kPa，应变：700-1140%，杨氏模量：8.6-14.8kPa，韧性：16.4-53.6kJ/m）可以通过调节 PCL 的功能度（双、三、四官能团）来轻松调节。有趣的是，基于水凝胶的可穿戴应变传感器具有高导电性（0.0550S/cm），对大（如关节弯曲）和微妙的人体运动（如皱眉和说话）都有敏感的响应。基于这些研究成果，本工作为开发具有粘附性、可控机械性能和高应变敏感性的水凝胶提供了新的思路，可作为一种灵活的、可穿戴的水凝胶应变传感器。
