The behavior of a temperature-sensitive micro-channel have been investigated in this study which mainly includes a functionally graded (FG) hydrogel as a sensor or an actuator. In order to achieve this goal, both fluid-structure interaction (FSI) and non-FSI simulations are conducted for hydrogel with homogeneous property distribution as well as FG hydrogels with different number of layers (2–16 layers). Moreover, this study investigates the FG hydrogel cross-linking density that obeys a general exponential form. In addition to all mentioned, the FG hydrogels are considered in both ascending and descending states with vertically and horizontally functionally graded property distributions (VFG and HFG hydrogels). Subsequently, the importance of the difference between the FG and homogenous hydrogels has been highlighted in the findings of the study. Besides, the FSI influence has a vital role in these structures especially once an FG material is utilized. According to the findings, the ascending and descending distributions of the hydrogel properties may significantly affect the micro-channel behavior, especially in horizontally graded type. This process can be done in a way that for descending distribution of HFG there exist no closing state for the micro-channel.
In this work, fluid–structure interaction (FSI) simulations, as well as non-FSI ones, are conducted to study the behavior of a functionally graded (FG) pH-sensitive micro-valve. The FEM analysis of the hydrogel is performed in ABAQUS while the fluid domain is analyzed in ANSYS fluent. To investigate the FSI and FG effects, both FSI and non-FSI simulations are performed for pH-sensitive micro-valve with homogeneous cross-linking distribution beside the FG cases. Two simulation domains are coupled by using a third-party software named MpCCI for both FSI and non-FSI simulations. For the FG hydrogel, linear and exponential property distributions are considered. The obtained results show a significant difference between the FG and homogeneous hydrogel behavior for both simulation methods. Additionally, the results emphasize that FSI consideration has a crucial role in the design of these smart devices. Especially, remarkable difference is observed for the closing pH of the micro-valve as well as the flow-rate diagrams. For example, a leakage is observed in FSI simulations for the closing pH of the non-FSI simulations that indicates the importance of the FSI effect. Finally, the effect of the cross-linking density distribution and the inlet pressure of micro-valve are studied and the results are analyzed.
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