Due to the incorporation of magnetic nanoparticles (MNPs), magnetically tuneable hydrogels have attracted considerable attention recently due to their ability to undergo remotely controlled large deformation. This work investigates the mechanics of the large deformation from the thermodynamics perspective for magneto-thermal sensitive hydrogels. The chemical thermodynamics of a temperature sensitive gel is first recapped before moving on to the thermodynamics of magnetism. Furthermore, an explicit energy form for the magneto-thermal sensitive hydrogel is adopted. The proposed field theory is implemented in a finite element method through the UHYPER subroutine. The finite element simulation results have been validated with analytical solutions at various temperatures and magnetic field strengths for MNPs entrapped PNIPAM hydrogel. We also utilize the numerical models to explain the interesting phenomena, including micro valves, bifurcation, and the opening of gel capsule for drug release delivery. The numerical deformation pattern for bifurcation is consistent with the experimental pattern, thus illustrating our theory and numerical method can provide future perspectives for device design of magneto-thermal sensitive hydrogel.

中文翻译：

---

磁热敏水凝胶的非均匀大变形研究

由于磁性纳米粒子（MNPs）的加入，磁性可调谐水凝胶最近因其能够进行远程控制的大变形而引起了相当大的关注。这项工作从热力学的角度研究了磁热敏水凝胶的大变形力学。在继续讨论磁性的热力学之前，首先回顾一下温度敏感凝胶的化学热力学。此外，采用了磁热敏感水凝胶的显式能量形式。所提出的场论是通过 UHYPER 子程序以有限元方法实现的。有限元模拟结果已在不同温度和磁场强度下对 MNP 包埋的 PNIPAM 水凝胶进行了分析解决方案验证。我们还利用数值模型来解释有趣的现象，包括微阀、分叉和用于药物释放递送的凝胶胶囊的开口。分叉的数值变形模式与实验模式一致，从而说明我们的理论和数值方法可以为磁热敏水凝胶的装置设计提供未来的视角。