Biomimetic Hydrophilic Islands for Integrating Elastomers and Hydrogels of Regulable Curved Profiles

Recent advances in integrating elastomers and hydrogels have enabled numerous emerging and promising applications in ionotronics, soft machines, and soft robotics. A challenge has emerged to integrate elastomers and hydrogels of intricate configurations in various manufacturing processes. Here, a biomimetic strategy is reported to enable the integration of elastomers and hydrogels with regulable curved profiles. To do so, hydrophilic islands are imparted on the hydrophobic surface of an elastomer to allow the regulation of the profiles of the precursor, which can be cured into a hydrogel with high degree of fidelity of the profile and robust adhesion between the hydrogel and the elastomer. Parametric investigations pertaining to the diameter of the hydrophilic island and the volume of the liquid are first carried out to construct the designing space, which is then applied to a hydrogel precursor. An ionotronic luminescent array that can selectively light up in response to various extents of compression is fabricated. A soft tunable lens whose focal length can be mediated by the profile and mechanical stretch is also demonstrated. The proposed approach paves avenues for integrated elastomer–hydrogel hybrid systems.