Acoustic wave propagation from external solution into a hydrogel can generate acoustic radiation stress due to acoustic momentum transfer between the two media

which may result in the large deformation of the hydrogel. To analyze the large deformation behavior of photo-thermal sensitive hydrogel under coupling acoustophoto-mechanical-thermo effect

an acousto-photo-mechanical-thermo constitutive model was established through the variational methods. Considering a specified case of photo-thermal sensitive hydrogel with uniaxial constraint

and that the condition of acoustic match was satisfied

the effects of ultrasonic intensity

light intensity and temperature on swelling properties of hydrogel had been analyzed systematically. The results show that the higher the uniaxial pre-stretching value is

the higher the equilibrium swelling ratio of the hydrogel is. The equilibrium swelling ratio of the hydrogel increases linearly with the rise of ultrasonic intensity

but decreases first and then increases with the temperature

and there is a minimum. The temperature at which the equilibrium swelling ratio reaches its minimum increases with the increase of pre-stretching and ultrasonic intensity

but decreases with the increase of light intensity. Once the environment temperature above the critical temperature

the change of pre-stretching and ultrasonic intensity has little effect on the swelling behavior of the hydrogel

but the change of light intensity still has a certain effect on the swelling behavior of the hydrogel.