fig3

Figure 3. Adhesion performance of ice-activated hydrogel suction cups. (A) Schematic diagram of PDMS suction cup contact process; (B) Schematic illustration of the evolution of interfacial contact in a hydrogel suction cup under freezing conditions; (C) Relative adhesion enhancement of the hydrogel suction cup and PDMS under low-temperature conditions. The annotations (~55 and ~0) indicate the approximately 55-fold increase in adhesion strength of the hydrogel suction cup after ice activation and the nearly negligible adhesion strength of PDMS at low temperature, respectively; (D) Adhesion of hydrogel suction cups at -20 °C after different freezing times; (E) Adhesion of hydrogel suction cups on different substrates; (F) Schematic illustration of ice-activated hydrogel suction cup contact on a cracked surface; (G) Adhesion of ice-activated hydrogel suction cup contact on surfaces with different crack sizes; (H) Schematic illustration of ice-activated hydrogel suction cup contact on a hole surface; (I) Adhesion of ice-activated hydrogel suction cup contact on surfaces with different hole sizes. Error bars represent ± SD (n = 3). PDMS: Polydimethylsiloxane; SD: standard deviation; PPX: parylene.