The swelling and shrinking of spherical thermo-responsive hydrogels

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Butler, Matthew D. and Montenegro-Johnson, Thomas D. (2022) The swelling and shrinking of spherical thermo-responsive hydrogels. Journal of Fluid Mechanics, 947. A11. ISSN 0022-1120 (https://doi.org/10.1017/jfm.2022.641)

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Abstract

Thermo-responsive hydrogels are a promising material for creating controllable actuators for use in micro-scale devices, since they expand and contract significantly (absorbing or expelling fluid) in response to relatively small temperature changes. Understanding such systems can be difficult because of the spatially and temporally varying properties of the gel, and the complex relationships between the fluid dynamics, elastic deformation of the gel and chemical interaction between the polymer and fluid. We address this using a poro-elastic model, considering the dynamics of a thermo-responsive spherical hydrogel after a sudden change in the temperature that should result in substantial swelling or shrinking. We focus on two model examples, with equilibrium parameters extracted from data in the literature. We find a range of qualitatively different behaviours when swelling and shrinking, including cases where swelling and shrinking happen smoothly from the edge, and other situations that result in the formation of an inwards-travelling spherical front that separates a core and shell with markedly different degrees of swelling. We then characterise when each of these scenarios is expected to occur. An approximate analytical form for the front dynamics is developed, with two levels of constant porosity, that well-approximates the numerical solutions. This system can be evolved forward in time, and is simpler to solve than the full numerics, allowing for more efficient predictions to be made, such as when deciding dosing strategies for drug-laden hydrogels.

ORCID iDs

Butler, Matthew D. ORCID logoORCID: https://orcid.org/0000-0002-7110-163X and Montenegro-Johnson, Thomas D.;
  • Item type:Article
    ID code:94994
    Dates:
    Date
    Event
    25 September 2022
    Published
    17 August 2022
    Published Online
    19 July 2022
    Accepted
    Subjects:Science > Mathematics
    Department:Faculty of Science > Mathematics and Statistics
    Depositing user: Pure Administrator
    Date deposited:11 Dec 2025 15:49
    Last modified:06 Feb 2026 14:43
    URI:https://strathprints.strath.ac.uk/id/eprint/94994
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