Yew Y K, Ng T Y, Li Hua, Lam K Y
Institute of High Performance Computing, Agency for Science Technology & Research, 1 Science Park Road, Singapore, 117528, Singapore.
Biomed Microdevices. 2007 Aug;9(4):487-99. doi: 10.1007/s10544-007-9056-4.
In this paper, we carry out the theoretical electro-chemo-mechanical investigation into water swollen ionic polymer gels under the simultaneous influence of electrical and chemical stimuli. In addition to these hydrogels being deployed as active sensing/actuating elements in MEMS/BioMEMS devices, this work can also serve as the basis of illustrating synthetic analogs of physiological muscles with possible applications in orthotics, prosthetics, and as artificial muscles. An electro-chemo-mechanical model or Multi-Effect-Coupling of pH Stimulus (MECpH) model, which was developed earlier by the present authors, is significantly extended to handle nonlinear deformation and implemented numerically to simulate the deformation characteristics of the pH-stimulus responsive hydrogel under the application of an externally applied voltage in different buffered pH solutions. The nonlinear deformation theory provides more accurate results especially when the deformations are large. The hydrogel is observed to experience swelling and bending when pH and external electric field stimuli coexist. The mode and degree of deformation are found to be highly dependent on changes of environmental pH, external electrical potential and bathing ionic strength. As an anionic hydrogel is considered in the simulation, it shows larger changes in deformation characteristic in basic than in acidic solutions. More importantly, the average curvatures of the swollen hydrogel are found to be a linear function with the applied electric potential, making the hydrogel an ideal actuator. However, we also note a significant decrease in the swelling equilibrium degree as the ionic strength becomes concentrated.
在本文中，我们对电刺激和化学刺激同时作用下的水溶胀离子聚合物凝胶进行了理论上的电化学-力学研究。除了这些水凝胶被用作微机电系统/生物微机电系统设备中的有源传感/驱动元件外，这项工作还可作为说明生理肌肉的合成类似物的基础，在矫形器、假肢以及作为人工肌肉方面可能具有应用价值。作者先前开发的一种电化学-力学模型或pH刺激多效应耦合（MECpH）模型得到了显著扩展，以处理非线性变形，并通过数值方法实现，用于模拟在不同缓冲pH溶液中施加外部电压时pH刺激响应水凝胶的变形特性。非线性变形理论能提供更准确的结果，尤其是在变形较大时。观察到当pH值和外部电场刺激共存时，水凝胶会发生溶胀和弯曲。发现变形的模式和程度高度依赖于环境pH值、外部电势和浸泡离子强度的变化。由于在模拟中考虑的是阴离子水凝胶，它在碱性溶液中的变形特性变化比在酸性溶液中更大。更重要的是，发现溶胀水凝胶的平均曲率与施加的电势呈线性函数关系，这使得水凝胶成为一种理想的驱动器。然而，我们也注意到随着离子强度的增加，溶胀平衡度会显著降低。
