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

Abstract

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.

Stretchable Transparent Polyelectrolyte Elastomers for All‐Solid Tunable Lenses of Excellent Stability Based on Electro–Mechano–Optical Coupling

“…Recall that during the molding‐free fabrication, the initial profile of the plano‐convex lens is almost identical with that of the precursor. Because the profile of the precursor can be tailored simply by mediating the size of plasma‐etching zone and the volume of the precursor (Figure S8, Supporting Information), [ 35 ] the molding‐free procedure thus provides a facile yet effective method to regulate the focal length of the tunable lens. Also worth mentioning is that the EDLs can withstand a voltage on the order of 1 V while the working voltage of the lens is on the order of 1 kV.…”

Patterning meets gels: Advances in engineering functional gels at micro/nanoscales for soft devices

“…The contact of different electrodes to turn on electroluminescence was determined by the local compression, leading to touchtriggered display. 46 For photopatterning of hydrogel electrodes, Zhang group explored DMD projection approach to pattern elastic PAM/PAA-Ca 2+ hydrogels, which were attached onto Au nanowire electrodes and organic semiconductors to achieve pressure sensing in a resistive 47 or a capacitive transistorbased manner. 48 With the micropatterned structures, these soft devices exhibited high sensitivity and could serve as wearable pulse monitoring devices.…”

“…Zhang et al utilized a facile dewetting method to form arrays of hydrogel electrodes with varied heights on hydrophobic PDMS encapsulating luminescent particles. The contact of different electrodes to turn on electroluminescence was determined by the local compression, leading to touch‐triggered display 46 …”

A mobile magnetic pad with fast light-switchable adhesion capabilities

“…Next, the PNIPAM hydrogel was deposited into the cavities of the magnetic PDMS substrate. The challenge of this process is to achieve stable bonding between PDMS substrate and hydrogel coating due to the intrinsic repel [26][27][28][29][30] (i.e. poor interfacial bonding) between hydrophobic PDMS [31,32] and hydrophilic hydrogel [33][34][35][36][37][38].…”