Fig. 5: The effect of AWH-H mass and stiffness on acoustic signal attenuation and energy efficiency of water extraction.

a A setup for measuring transmittance and attenuation of acoustic waves propagating through hydrogel samples. A sample is placed between the actuator (transmitter) and a sensor (receiver), and the transmitted signal is measured as the output voltage. b Input and output voltages measured under periodic actuation of an HG-A sample. c The output voltage as a function of hydrogel stiffness and thickness. The COMSOL-simulated sound pressure level intensity (a.u.) in the hydrogel is shown in the inset for HG-A. d,e Water extraction rates from HG-A and HG-C gels and the corresponding energy consumption during ultrasonic actuation with 70% duty cycle. f Anomalous diffusion model describes the moisture extraction process under ultrasonic actuation. g,h Extraction rates and the associated energy costs during actuation with 30% duty cycle. i Cyclic stability of the desorption behavior of HG-A hydrogel. Scale bar: 16 mm.