Anti-freezing heat-resistant hollow hydrogel tubes.

Hollow hydrogel tubes that are capable of maintaining their flexibility and structural stability in extreme temperature conditions, have a potential for use in biomedical scaffolds, carriers, and soft robotics over a wide temperature range. However, the preparation of hollow hydrogel tubes still remains challenging because it normally requires templates or complex devices, and is hard to endow the hollow tubes with anti-freezing heat-resistant capabilities. We report a protocol that does not require template or complex devices, in which sodium alginate (SA) film strips are immersed in an aqueous mixture of CaCO3, CaCl2, NaHCO3 and HCl which results in the manufacture of hollow tubes in 30 min. These hollow tubes are functionalized by glycerol and polyethylene glycol that provide the tubes with anti-freezing heat-resistant performances and enables them to keep their flexibility and hollow structures from -70 to 120 °C. This is the first report on anti-freezing heat-resistant hollow hydrogel tubes, to the best of our knowledge. Such hollow tubes as carriers can control the sublimation of mothball at a rate of 1.1 mg/h that is one tenth of the sublimating rate of an unloaded mothball. This sublimating rate reduces the hazard to environments with maintaining the repellent effects. As the tube is a honey carrier, it enables the sustainable release of the honey over 800 min with a high efficacy for tricking and capturing ants. This is ~14 times longer than the same amount of unloaded honey would release. The simple applications demonstrate that the anti-freezing heat-resistant hollow tubes might be feasible as carriers for the controlled release in extremely cold/hot environments.