Bending force enhancement of sodium alginate-based polymer gel paper actuators

This work mainly studies the effect of calcium chloride crosslinking on the bending force properties of sodium alginate-based polymer gel paper actuators (PGPAs), where the driving layer is fabricated by the method of freeze-drying. The results indicate that the concentration of the crosslinking solution strongly affects the performance of the PGPAs and inappropriate concentration of crosslinking solution will even lead to a lower bending force of the PGPA compared with the uncrosslinked one. In particular, the bending force of excessively crosslinked PGPAs is lower than that of uncrosslinked actuators. The bending force of the PGPA achieves the highest value of 3.14 mN (1.94 times than when uncrosslinked) when the concentration of the crosslinking solution is 2 wt%. The driving layer of the PGPA shows optimal performance when the concentration of crosslinking solution is 2 wt%, and the elastic modulus of the driving layer was the smallest under this condition. Compared to the uncrosslinked actuators, the PGPAs consume less force to resist the bending strain produced. The pore structure of the driving layer is more uniform, and the connectivity between the pores is better, which is favorable for the bending force output of the PGPA. Moreover, compared with other concentrations of the crosslinking solution, the 2 wt% crosslinking solution leads to a desirable specific capacitance of the driving layer, which is beneficial for the movement of internal ions. Therefore, the bending force of the PGPA is improved.