3D打印导电水凝胶的制备与应变传感性能研究

  导电水凝胶柔性应变传感器因具备优异的柔韧性、可拉伸性等优势，被广泛应用于人体运动、生理信号的实时监测，在健康医疗设备、可穿戴电子器件等领域具有广阔的应用前景。然而，借助模具的冻融法、紫外光聚合法等传统工艺制备的导电水凝胶柔性应变传感器存在着制备成本高、耗时、设计自由度低等缺点，极大地限制了柔性应变传感器的个性化应用和发展。与传统工艺相比，光固化3D打印技术避免了开模和脱模的过程，具有成本低、成型速度快和结构设计度高的优势，为水凝胶柔性应变传感器的制备提供了一种新的策略。针对目前光固化3D打印水凝胶柔性应变传感器存在光敏树脂浆料受限、水凝胶生物相容性差、灵敏度低、缺乏保水性、回弹性和可穿戴性差等问题，本文开发了一种具有潜在生物相容性的光固化3D打印水凝胶；构建了导电填料与水凝胶不同的复合方式来提升应变传感器的灵敏度；设计并调控物理和化学交联网络来优化水凝胶的保水、回弹等使用性能；通过结构设计来提升应变传感器的可穿戴、机械和传感性能。论文的主要研究内容和结果如下：

  基于光固化3D打印水凝胶浆料的选择原则，制备了N-丙烯酰吗啉水凝胶(P(ACMO))、甲基丙烯酸羟乙酯水凝胶(P(HEMA))和聚乙二醇二丙烯酸酯水凝胶(P(PEGDA))，比较了不同水凝胶的拉伸性、自粘附性和生物相容性，研究了不同水凝胶的内部交联机制和拉伸断裂机制。P(ACMO)水凝胶在拉伸过程中的受力点为链段与水之间形成的弱氢键作用，氢键的可逆断裂/重组赋予了P(ACMO)水凝胶优异的机械拉伸性。此外，P(ACMO)水凝胶展示出潜在的自粘附性和生物相容性。光固化3D打印P(ACMO)水凝胶的开发为后续导电填料的引入和柔性应变传感器的制备奠定基础。

  设计了不同类型的填料嵌入式和涂层负载式的导电水凝胶，制备了电子、离子和电子/离子混合导电型P(ACMO)水凝胶，比较了不同导电类型水凝胶的电学、机械和传感性能，揭示了不同导电类型水凝胶的传感机制。单一的填料嵌入或涂层负载式导电水凝胶在应变过程中导电路径变化有限，导电机制始终为电子或离子导电，而混合型导电水凝胶在应变过程中会发生电子和离子导电机制的相互转换，显著提升了应变传感器的灵敏度。设计的金属涂层负载/NaCl嵌入P(ACMO)导电水凝胶在0-20%和20-100%应变范围的灵敏度系数分别为2.4 × 10⁵和5.0 × 10⁴，为高性能水凝胶柔性应变传感器的设计和开发奠定基础。

  基于水凝胶的物理和化学交联机制，探究了甘油和PEGDA的含量对水凝胶的保水、自粘附、回弹等使用性能的影响规律，揭示了水凝胶的保水、自粘附和回弹机制。由于甘油的吸水特性和桥接作用，水凝胶的保水性和自粘附性得到了明显的改善。由P(ACMO)与PEGDA之间形成的共价交联网络和P(ACMO)/PEGDA与甘油/水之间形成的氢键的协同作用机制赋予了水凝胶优异的回弹性，混合导电水凝胶在100%拉伸应变下的初始残余应变仅为9.3%。P(ACMO)导电水凝胶保水性、自粘附性、回弹性等使用性能的优化为后续高性能可穿戴水凝胶应变传感器的设计和开发奠定基础。

  设计了不同结构水凝胶，有限元分析了不同结构水凝胶的应力和应变分布，探究了不同结构对水凝胶的重量、透气、机械和传感性能的影响规律。有限元分析表明，方格结构水凝胶在拉伸过程中应变分布均匀，通过机械性能测试也表明了方格结构水凝胶具有优异的回弹性，在100%拉伸应变下的初始残余应变仅为7.8%。此外，方格结构设计还同时改善了水凝胶应变传感器的穿戴透气性、灵敏度和传感稳定性。在手指康复监测、手语识别、人机交互等领域对光固化3D打印方格结构导电水凝胶柔性应变传感器进行了初步的应用。

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