Figure 3: Characterization of the hydraulic hydrogel actuators under cyclic actuations.
From: Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water
(a) Pressure-volume hysteresis curve and the resultant energy analysis for the unit-segment hydrogel actuator. (b) Pressure-volume hysteresis curve and the resultant energy analysis for the bending hydrogel actuator. (c) Pressure-volume hysteresis curves for the bending hydrogel actuator in the 1st, 10th, 100th and 1,000th cycles of actuations with the actuation frequency of 0.5 Hz. (d) The number of cycles to failure for the PAAm-alginate hydrogel versus the applied nominal stress. The cyclic fatigue tests are performed using stress-controlled cyclic tension of the hydrogel samples at a frequency of 1 Hz. The dotted line indicates the maximum stress level in the fully actuated hydrogel actuator in Fig. 2a. Note that hydrogel actuators in a,b are dyed with colour for better visual representation.
