On‐Demand Activation of Thin Alginate Shell Encapsulated Volatile Liquid for Untethered Pneumatic Soft Actuation

Phase‐changing liquids in elastomeric matrices have drawn attention for facilitating pneumatic actuators that circumvent the need for tethering in soft robotics. Phase change from liquid to vapor enables high‐power, self‐contained actuation triggered by minimal temperature change. However, due to the volatile nature of the phase‐changing liquids, simple fabrication methods that ensure both long‐term volatile liquid storage and reliable on‐demand activation are beneficial. We present a straightforward method for encapsulating Novec7000, a nonhazardous volatile liquid with a boiling point of 34°C, within micron‐thin alginate shells. The alginate‐Novec7000 capsules are prepared through in situ injection of Novec7000 during ionic crosslinking of sodium alginate, followed by ambient drying. These capsules remain intact during extended storage (over 7 months) and can be activated on‐demand either mechanically (with two to six newtons of compressive force) or thermally (above the volatile liquid's boiling point). This approach prevents the loss of volatile liquids for pneumatic phase‐change soft robots until actuation is desired. Demonstrations highlight alginate‐Novec7000 capsule utility in embedding volatile liquids into elastomeric matrices, enabling thermally activated pneumatic valves used as a high‐temperature safeguard in pipe systems. On‐demand release of volatile liquids can expand the utility of untethered self‐contained pneumatic phase‐change soft robotics and enable new applications.