Rapid Soft Material Actuation Through Droplet Evaporation

Soft material actuation is a promising field that can potentially solve several limitations of traditional robotic systems. These systems comprise soft and flexible materials to achieve high degrees of freedom and compliance with their surroundings. One method to actuate such structures is to vaporize liquid that is embedded inside the soft material. The soft elastomers are inflated since the generated vapor occupies a much larger volume after phase transformation. The simplest and widely used design to vaporize such liquids is installing a heating element near the liquid. Heating the system beyond the boiling point rapidly boils the liquid and deforms the structure. However, this technique possesses several limitations, such as the heating element must be in the liquid's vicinity, and boiling the liquid requires high temperatures. In addition, embedding a small amount of liquid for faster boiling prevents the use of valves to exhaust the vapor. Instead, the structure is slowly cooled until it returns to its original position. In this study, these limitations are addressed by combining heating with vibrating mesh atomization. The atomizer disperses the liquid into small droplets, which vaporize much faster as compared with simply heating the bulk liquid. Actuation through vibrating mesh atomization was first characterized and compared with other techniques. Then, the introduced method was used to demonstrate cyclic actuation, and a bistable structure was designed and fabricated to demonstrate gripping motion.