Poly(N‐isopropylacrylamide) (PNIPAm) is widely implemented in responsive soft actuators. However, there are still defects of low brittleness and poor mechanical properties. Moreover, little attention has been paid to diameter shrinkage deformation of tubular PNIPAm hydrogels. In this study, physical crosslinking between Ca2+ cations and sodium alginate (SA) was introduced to form an interpenetrating network with chemically crosslinked PNIPAm, and then Ca–alginate/PNIPAm hydrogels were prepared. Molecular structure, surface morphology, swelling properties and mechanical properties were characterized. The results indicated that the pure PNIPAm hydrogel obtained using thermal initiation polymerization had better swelling and temperature‐responsive properties (with a maximum swelling ratio of 1134.65% and a fastest decrease rate of 318.45% min−1 in swelling ratio) compared to the hydrogel using ultraviolet polymerization. The mechanical properties the Ca/PNIPAm hydrogel were enhanced until the SA concentration exceeded 8 wt%. The compressive modulus of the hydrogel with SA concentration of 8 wt% (16.61 kPa) was increased by 10 times as compared with the pure PNIPAm hydrogel (1.42 kPa), and its corresponding elastic modulus increased by 47%. Moreover, a model soft actuator was prepared based on annular and tubular hydrogels. It had reversible diameter shrinkage behavior at 50 °C, and excellent temperature‐responsive property. The results reported herein provide valuable insight into the engineering application of temperature‐responsive PNIPAm‐based hydrogels. © 2022 Society of Industrial Chemistry.

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Soft materials are widely used in biomedical and flexible electronics fields, while their deformation properties are affected by many factors. It is difficult to obtain accurate characteristic parameters using common test methods. In this work, polydimethylsiloxane is used as the tested object, and the samples with different mass ratios of curing agent/base and thicknesses are prepared. The deformation properties of polydimethylsiloxane under the conditions of different loads and two indenters are investigated using the experiment and finite element analysis, and the factors affecting its deformation properties are discussed. The results demonstrate that the elastic modulus of polydimethylsiloxane is positively correlated with the content of curing agent, and the load has no significant role in its deformation properties. The correlation coefficients between the indentation tests and finite element results are in excess of 0.92. The difference between the modulus of the spherical indentation mode and the elastic modulus of the standard tensile test is lower than 3 %, while the flat‐ended indentation mode is more applicable to characterizing deformation properties of soft materials with variable thickness. These results will provide a new insight into the deformation characterization of soft materials.