Finite bending of bilayer pH-responsive hydrogels: A novel analytic method and finite element analysis

Abstract

Recently bilayer smart hydrogel beams are widely used in various applications such as sensors, actuators, self-folding structures and switches. Developing a strong tool for designing these bilayer smart hydrogel beams is necessary. In this article, we developed an analytical method to solve the swelling induced bending of bilayer beams made of a pH-sensitive layer attached to an inert elastomer layer. A total deformation gradient tensor, without assuming any intermediary virtual state, is defined to map the initial configuration to the deformed state. An exponential function with four constants is employed to describe the deformation of the pH-sensitive gel layer. The proposed method leads to a system of equations with six unknowns that can be simply solved via numerical techniques. As a case study, this method is implemented to solve the swelling induced bending of several bilayer beams with various parameters. The outcomes of the analytical solution are in excellent agreement with the finite element method results, thus confirming the strength of the presented method.

Developing an analytical solution for photo-sensitive hydrogel bilayers

“…Another solution method is also suggested in which the multiplicative decomposition is omitted, and the large deformation of bilayers is analyzed through a single-step deformation. In comparison to the previous methods, the latter’s results were more coincident with numerical simulations (Abdolahi et al, 2016, 2017; Arbabi et al, 2017). In this work, the formulation is derived based on a single-step deformation, considering both the bending and free swelling.…”

Transformer Hydrogels: A Review

“…While previously discussed principles can generate complex hydrogel shape transformations, they require integration of two or more materials with seams or interfaces between them. Seamless integration of materials can be important from a failure perspective since the interfaces between materials can fracture and delaminate due to high interfacial stresses resulting from the significant differences in mechanical and chemical properties and swelling characteristics . Biological structures avoid these critical problems by employing gradients where properties vary spatially almost homogeneously within the same material system …”

Plastic Bending at Large Strain: A Review

“…Analytic and semi-analytic solutions for finite bending of various hydrogel strips were found in [16][17][18][19][20]. An elastomer-hydrogel bi-layer strip was considered in [16], a hydrogel-elastomer-hydrogel tri-layer strip in [17], and a functionally graded hydrogel strip in [18].…”