[99]. Zhao ZH, Zhu SF, Li B, Niu CG, Tong Y, Ma N, Dong XF*, Han BG, Huang H, Qi M*, A Stiffness Tunable Self-Healing Composite Comprising PDMS and Titanium Dioxide, ACS Applied Polymer Materials, 2022, 4: 2656-2663.

Abstract: It is a challenge to make artificial muscles with tunable stiffness capacities. The key is to develop a composite with tunable stiffness as well as self-healing properties and stretchability. In this work, we design a composite with amorphous TiO2 particles and poly(dimethylsiloxane) (PDMS) matrix cross-linked with metal–ligand interactions. The PDMS matrix enables the composite to have self-healing properties and excellent stretchability, while the interactions between the TiO2 particles can be enhanced by applying an electric field, which provides the composite with an electric field-controlled stiffness. The tunable storage modulus increased by 180% at 4 kV/mm. The stiffness of a simply supported beam increased by 10.8% at 6 kV with respect to that at 0 kV. Based on its tunable stiffness, self-healing properties and stretchability, this composite can mimic many functions of human muscles and has promising applications as an artificial muscle.

https://pubs.acs.org/doi/10.1021/acsapm.1c01937